Showing papers in "European Journal of Clinical Pharmacology in 2000"

Pharmacokinetics of quercetin from quercetin aglycone and rutin in healthy volunteers.

Abstract: Background: Quercetin is a flavonoid with a wide range of biological activities. It mainly occurs in plants as glycosides, such as rutin (quercetin rutinoside) in tea. Quercetin and rutin are used in many countries as vasoprotectants and are ingredients of numerous multivitamin preparations and herbal remedies. Objectives: The primary objective was to characterise and compare the absorption and the pharmacokinetics of quercetin from quercetin aglycone and rutin. A secondary objective was to investigate which forms of quercetin are present in plasma. Methods: In this double blind, diet-controlled, two-period cross-over study, 16 healthy volunteers received three different doses of quercetin and rutin orally. The doses corresponded to 8 mg, 20 mg and 50 mg quercetin aglycone. Blood samples were obtained between 0 h and 32 h post-dose. Results: The overall kinetic behaviour of quercetin differed remarkably after ingestion of quercetin aglycone or rutin. The mean area under the plasma concentration–time curve from 0 h to 32 h [AUC(0–32)] and maximum plasma concentration (Cmax) values of the two treatments were similar. However, time to reach Cmax (tmax) was significantly shorter after the quercetin aglycone treatment than after the rutin treatment (1.9, 2.7 and 4.8 versus 6.5, 7.4 and 7.5 h, for doses 1, 2 and 3, respectively). Also, the absorption of quercetin from quercetin aglycone was predictable and inter-individual variation was small. In contrast, after ingestion of rutin, inter-individual variations in AUC(0–32) and Cmax values were considerable and seemed to be associated with gender and use of oral contraceptives. Quercetin and rutin were found in plasma as glucuronides and/or sulfates of quercetin and as unconjugated quercetin aglycone, but no rutin was detected. Conclusions: In clinical trials, studying the effects of quercetin from rutin, bioavailability must be taken into consideration and plasma quercetin concentrations monitored. Whether our results apply to other glycosidic drugs as well, especially other rutosides, should be investigated.

Pharmacokinetics and organ distribution of intravenous and oral methylene blue.

Abstract: Objective: To determine the pharmacokinetics and organ distribution of i.v. and oral methylene blue, which is used to prevent ifosfamide-induced encephalopathy in oncology. Methods: The concentration of methylene blue in whole blood was measured using high-performance liquid chromatography in seven volunteers after i.v. and oral administration of 100 mg methylene blue with and without mesna. The distribution of methylene blue in different tissues was measured in rats after intraduodenal and i.v. application. Results: The time course of methylene blue in whole blood after i.v. administration showed a multiphasic time course with an estimated terminal half-life of 5.25 h. Following oral administration, the area under the concentration–time curve was much lower (9 nmol/min/ml vs 137 nmol/min/ml). Co-administration of mesna, which could influence distribution by ion-pairing, did not alter the pharmacokinetics. The urinary excretion of methylene blue and its leucoform was only moderately higher after i.v. administration (18% vs 28% dose). Intraduodenal administration to rats resulted in higher concentrations in intestinal wall and liver but lower concentrations in whole blood and brain than i.v. methylene blue. Conclusions: Differences in organ distribution of methylene blue are mainly responsible for the different pharmacokinetics after oral and i.v. administration. If methylene blue acts in the liver, where ifosfamide is primarily activated to reactive and potentially toxic metabolites, oral and i.v. methylene blue are likely to be equally effective. However, if the site of action is the central nervous system, i.v. methylene blue which results in much higher concentrations in brain seems preferable.

Evidence of clinical efficacy of homeopathy. A meta-analysis of clinical trials. HMRAG. Homeopathic Medicines Research Advisory Group.

Abstract: Objective: To establish, using a systematic review and meta-analysis, whether there is any evidence from randomised controlled clinical trials of the efficacy of homeopathic treatment in patients with any disease.

QT-interval prolongation by non-cardiac drugs: lessons to be learned from recent experience.

Abstract: Background: Evidence has accrued that several non-cardiac drugs may prolong cardiac repolarisation (hence, the QT interval of the surface electrocardiogram) to such a degree that potentially life-threatening ventricular arrhythmias (e.g. torsades de pointes) may occur, especially in case of overdosage or pharmacokinetic interactions.

The consumption of drugs by 75-year-old individuals living in their own homes

Abstract: Objective: To examine the drug consumption and the extent of polypharmacy (defined as daily intake of three or more drugs) among 75-year-old persons living in their own homes and to point out potential problems associated with it.

Adverse drug reactions in a department of systemic diseases-oriented internal medicine: prevalence, incidence, direct costs and avoidability.

Abstract: Objective: Adverse drug reactions (ADRs) are a major cause of hospital admission and in-hospital morbidity. Departments of internal medicine are at the forefront of this problem. To increase the knowledge base, we did a study of the frequency, hazard function, avoidability, and cost of ADRs as a cause for admission in internal medicine, or when occurring after admission. Methods: This prospective cohort study was based on all admissions to an internal medicine unit over a 4-month period. Patients were intensively followed in order to assess any ADR occurring during the hospital stay. Causality, direct costs, and preventability were assessed. Results: Of 444 admissions (2569 patient-days), 156 ADRs occurred in 116 patients (26.1% of all admissions); 95 (21.4%) of these had ADRs at admission, which were the reason for admission in 32 (7.2%). Twenty-one patients (4.7%) presented with 26 ADRs during hospitalization. The in-hospital ADR incidence rate was 10.1 per 1000 patient-days. The cost of ADRs leading to hospitalization was estimated at Euro 11,357 per hospital bed per year. Eighty percent of ADRs could be considered preventable. Conclusion: ADRs in hospitalized patients are common and often preventable. Since most ADRs occurred before admission, prevention strategies should preferentially target primary health care providers.

Inhibition of human cytochrome P450 enzymes by 1,4-dihydropyridine calcium antagonists: prediction of in vivo drug–drug interactions

Abstract: Objective: 1,4-Dihydropyridine calcium antagonists such as nifedipine are potent vasodilators. It is now commonly agreed that the oxidation of 1,4-dihydropyridine into pyridine, which is one of the main metabolic pathways, is catalysed by the cytochrome P450 (CYP) 3A4 isoform. In the present study, the inhibitory effects of 13 kinds of 1,4-dihydropyridine calcium antagonists clinically used in Japan on human CYP-isoform-dependent reactions were investigated to predict the drug interactions using microsomes from human B-lymphoblast cells expressing CYP. Results: The specific activities for human CYP isoforms included 7-ethoxyresorfin O-deethylation (CYP1A1), phenacetin O-deethylation (CYP1A2), coumarin 7-hydroxylation (CYP2A6), 7-benzyloxyresorufin O-dealkylation (CYP2B6), S-warfarin 7-hydroxylation (CYP2C9), S-mephenytoin 4′-hydroxylaion (CYP2C19), bufuralol 1′-hydroxylation (CYP2D6), chlorzoxazone 6-hydroxylation (CYP2E1), and testosterone 6β-hydroxylation (CYP3A4). Benidipine and amlodipine competitively inhibited the CYP1A1 activity. Nifedipine, nisoldipine and aranidipine competitively inhibited the CYP1A2 activity. No 1,4-dihydropyridie calcium antagonists used in this study inhibited the CYP2A6 activity. Barnidipine and amlodipine inhibited the CYP2B6 activity. Nicardipine, benidipine, manidipine and barnidipine competitively inhibited the CYP2C9 and CYP2D6 activities. Inhibition extent of the CYP2E1 activity by nifedipine and aranidipine were weak. Nicardipine, benidipine and barnidipine inhibited the CYP2C19 and CYP3A4 activities. Among the human CYP isoforms investigated, the inhibitory effects of 1,4-dihydropyridine calcium antagonists were potent on human CYP1A2, CYP2B6, CYP2C9, CYP2C19 and CYP2D6 as well as CYP3A4. Furthermore, the isoform selectivity of inhibition by 1,4-dihydropyridine calcium antagonists was clarified. Conclusions: In consideration of the K i values obtained in the in vitro inhibition study and the concentration of 1,4-dihydropyridine calcium antagonists in human liver, the possibility of in vivo drug interactions of nicardipine and other drugs which are mainly metabolised by CYP2C9 and/or CYP3A4 was suggested. The inhibition of human CYP isoforms by 1,4-dihydropyridine calcium antagonists except nicardipine might be clinically insignificant.

Pharmacokinetics of esomeprazole after oral and intravenous administration of single and repeated doses to healthy subjects.

Abstract: Objective: To study the pharmacokinetics of esomeprazole, one of the optical isomers of omeprazole, after 20 mg or 40 mg single and repeated oral and intravenous administration to healthy subjects. The main metabolites of esomeprazole were also assessed after the 40-mg oral dose. Methods: In two separate studies, 16 healthy male subjects and 16 healthy male and female subjects received intravenous doses of 20 mg and 40 mg esomeprazole, respectively, on the first investigation day. After a wash-out period of 5–14 days, the same doses (20 mg as a solution and 40 mg as a capsule) were given orally for 5 days and then again intravenously on day 6. Blood samples for determination of esomeprazole and its metabolites were collected 12 h or 24 h post-dose and were analysed using normal-phase liquid chromatography with ultraviolet (UV) detection. Pharmacokinetic parameters of esomeprazole and its metabolites were estimated using non-compartmental analysis. Geometric means and ratios of the geometric means together with 95% confidence intervals (CI) of the pharmacokinetic parameters were calculated using analysis of variance (ANOVA). Results: Plasma clearance (CL) of esomeprazole decreased from 22 l/h to 16 l/h and from 17 l/h to 9 l/h following repeated dosing of 20 mg and 40 mg, respectively. Total area under the plasma concentration–time curve (AUC) increased (from 1.34 µmol×h/l to 2.55 µmol×h/l) with absolute bioavailability (F) being 50% on day 1 and 68% on day 5 after the 20-mg oral dose. AUC increased (from 4.32 µmol×h/l to 11.21 µmol×h/l) with F being 64% on day 1 and 89% on day 5 after the 40-mg oral dose. The plasma levels for esomeprazole sulphone were substantially higher on day 5 than on day 1, while those for 5-hydroxy esomeprazole were marginally higher on day 5 than on day 1 following repeated oral dosing of 40 mg esomeprazole. No side effects attributable to esomeprazole were noticed. Conclusion: The increased AUC of esomeprazole with repeated dosing is probably due to a combination of a decreased first-pass elimination and a decreased systemic clearance.

Attitudes to reporting adverse drug reactions in northern Sweden.

Abstract: OBJECTIVES: This study was designed to investigate attitudes of general practitioners (GPs) and hospital physicians in Sweden towards spontaneous reporting of adverse drug reactions (ADRs). METHOD: ...

Pharmacokinetics and pharmacodynamics of a premixed formulation of soluble and protamine-retarded insulin aspart.

Abstract: Objective: With the aim to obtain a premixed rapid-acting insulin with a serum insulin profile more closely resembling the endogenous meal-stimulated serum insulin profiles, a 30/70 (rapid/intermediate-acting) premixed suspension of the rapid-acting insulin analogue insulin aspart (BIAsp30) was compared with a similar premixed suspension of biphasic human insulin 30/70 (BHI30) after a single subcutaneous injection.

Detecting drug–drug interactions using a database for spontaneous adverse drug reactions: an example with diuretics and non-steroidal anti-inflammatory drugs

Abstract: Objective: Drug–drug interactions are relatively rarely reported to spontaneous reporting systems (SRSs) for adverse drug reactions. For this reason, the traditional approach for analysing SRS has major limitations for the detection of drug–drug interactions. We developed a method that may enable signalling of these possible interactions, which are often not explicitly reported, utilising reports of adverse drug reactions in data sets of SRS. As an example, the influence of concomitant use of diuretics and non-steroidal anti-inflammatory drugs (NSAIDs) on symptoms indicating a decreased efficacy of diuretics was examined using reports received by the Netherlands Pharmacovigilance Foundation Lareb. Methods: Reports received between 1 January 1990 and 1 January 1999 of patients older than 50 years were included in the study. Cases were defined as reports with symptoms indicating a decreased efficacy of diuretics, non-cases as all other reports. Exposure categories were the use of NSAIDs or diuretics versus the use of neither of these drugs. The influence of the combined use of both drugs was examined using logistic regression analysis. Results: The odds ratio of the statistical interaction term of the combined use of both drugs was increased [adjusted odds ratio 2.0, 95% confidence interval (CI) 1.1–3.7], which may indicate an enhanced effect of concomitant drug use. Conclusion: The findings illustrate that spontaneous reporting systems have a potential for signal detection and the analysis of possible drug–drug interactions. The method described may enable a more active approach in the detection of drug–drug interactions after marketing.

Effect of fluconazole on plasma fluvastatin and pravastatin concentrations

Abstract: Objective: To study the effects of fluconazole on the pharmacokinetics of fluvastatin and pravastatin, two inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. Methods: Two separate randomised, double-blind, two-phase, crossover studies with identical study design were carried out. In each study, 12 healthy volunteers were given a 4-day pretreatment with oral fluconazole (400 mg on day 1 and 200 mg on days 2–4) or placebo, according to a randomisation schedule. On day 4, a single oral dose of 40 mg fluvastatin (study I) or 40 mg pravastatin (study II) was administered orally. Plasma concentrations of fluvastatin, pravastatin and fluconazole were measured over 24 h. Results: In study I, fluconazole increased the mean area under the plasma fluvastatin concentration–time curve (AUC0–∞) by 84% (P < 0.01), the mean elimination half-life (t 1/2) of fluvastatin by 80% (P < 0.01) and its mean peak plasma concentration (Cmax) by 44% (P < 0.05). In study II, fluconazole had no significant effect on the pharmacokinetics of pravastatin. Conclusions: Fluconazole has a significant interaction with fluvastatin. The mechanism of the increased plasma concentrations and prolonged elimination of fluvastatin is probably inhibition of the CYP2C9-mediated metabolism of fluvastatin by fluconazole. Care should be taken if fluconazole or other potent inhibitors of CYP2C9 are prescribed to patients using fluvastatin. However, pravastatin is not susceptible to interactions with fluconazole or other potent CYP2C9 inhibitors.

Effect of grapefruit juice dose on grapefruit juice-triazolam interaction: repeated consumption prolongs triazolam half-life.

Abstract: Objective: Grapefruit juice inhibits CYP3A4-mediated metabolism of several drugs during first pass. In this study, the effect of grapefruit juice dose on the extent of grapefruit juice–triazolam interaction was investigated. Methods: In a randomised, four-phase, crossover study, 12 healthy volunteers received 0.25 mg triazolam with water, with 200 ml normal-strength or double-strength grapefruit juice or, on the third day of multiple-dose [three times daily (t.i.d.)] administration of double-strength grapefruit juice. Timed blood samples were collected up to 23 h after dosing, and the effects of triazolam were measured with four psychomotor tests up to 10 h after dosing. Results: The area under the plasma triazolam concentration–time curve (AUC0–∞) was increased by 53% (P < 0.01), 49% (P < 0.01) and 143% (P < 0.001) by a single dose of normal-strength, a single dose of double-strength and multiple-dose administration of double-strength grapefruit juice, respectively. The peak plasma concentration (Cmax) of triazolam was increased by about 40% by a single dose of normal-strength grapefruit juice (P < 0.01) and multiple-dose grapefruit juice (P < 0.01) and by 25% by a single dose of double-strength grapefruit juice (P < 0.05). The elimination half-life (t 1/2) of triazolam was prolonged by 54% during the multiple-dose grapefruit juice phase (P < 0.001). A significant increase in the pharmacodynamic effects of triazolam was seen during the multiple-dose grapefruit juice phase in the digit symbol substitution test (DSST, P < 0.05), in subjective overall drug effect (P < 0.05) and in subjective drowsiness (P < 0.05). Conclusions: Even one glass of grapefruit juice increases plasma triazolam concentrations, but repeated consumption of grapefruit juice produces a significantly greater increase in triazolam concentrations than one glass of juice. Thet 1/2 of triazolam is prolonged by repeated consumption of grapefruit juice, probably due to inhibition of hepatic CYP3A4 activity.

Pharmacokinetics, COX-2 specificity, and tolerability of supratherapeutic doses of rofecoxib in humans.

Abstract: Objective: Prostaglandin synthesis is catalyzed by a constitutive cyclo-oxygenase isoform (COX-1) and an inducible isoform (COX-2). It is hypothesized that the analgesic and anti-inflammatory effects of nonsteroidal anti-inflammatory drugs (nonspecific COX-1/COX-2 inhibitors) such as ibuprofen principally derive from COX-2 inhibition. The purpose of this study was to evaluate steady-state pharmacokinetics, biochemical selectivity and tolerability of rofecoxib (VioxxTM), characterized in vitro as a COX-2 inhibitor. Methods: Four panels of healthy men (n=8 per panel) were administered rofecoxib (n=6) (25, 100, 250, 375 mg) or placebo (n=2) once daily on day 1 and days 3–14. Blood samples for assays of rofecoxib plasma concentration and COX isoform activity were obtained pre-dose and at specified time points post-dose. Results: Rofecoxib pharmacokinetics were found to be complex and nonlinear. Elimination half-life ranged from 9.9 h to 17.5 h after multiple dosing with an accumulation ratio close to 2 for all doses. COX-2 inhibitory activity as assessed by average inhibition of whole blood lipopolysaccharide-stimulated prostaglandin E2 over the 8-h post-dose period on day 14 was 0.3, 67, 96, 92 and 96% for the placebo and the 25-, 100-, 250- and 375-mg treatment groups, respectively. No treatment group showed significant inhibition of COX-1 as assessed by thromboxane B2 generation in clotting whole blood. Side effects were mild and transient. Conclusion: The results indicate that rofecoxib is a potent and specific inhibitor of COX-2 in humans even at doses more than tenfold higher than those associated with efficacy in patients with osteoarthritis.

Therapeutic monitoring of the new antiepileptic drugs.

Abstract: Objective: To discuss the potential value of therapeutic drug monitoring (TDM) of the new antiepileptic drugs gabapentin, lamotrigine, oxcarbazepine, tiagabine, topiramate, vigabatrin and zonisamide. Methods: A review of studies of the relationship between plasma concentrations and effects of new antiepileptic drugs is provided. Furthermore, the potential value of TDM of these drugs is discussed in relation to their mode of action and their pharmacokinetic properties. The various methods that are available for analysing plasma concentrations of the new antiepileptic drugs are also briefly reviewed. Results: The available information on the relationship between plasma concentrations and effects of the new drugs is scarce. For most drugs, wide ranges in concentrations associated with seizure control are reported, and a considerable overlap with drug levels among non-responders and also with concentrations associated with toxicity is often noted. However, very few studies have been designed primarily to explore the relationship between drug plasma concentrations and effects. Consequently, there are no generally accepted target ranges for any of the new antiepileptic drugs. Although the available documentation clearly is insufficient, the pharmacological properties of some of the drugs, in particular lamotrigine, zonisamide and, possibly, oxcarbazepine, topiramate and tiagabine, suggest that they may be suitable candidates for TDM. Conclusion: TDM of some of the new antiepileptic drugs may be of value in selected cases, although routine monitoring in general cannot be recommended at this stage. Further systematic studies designed specifically to investigate concentration–effect relationships of the new antiepileptic drugs are urgently needed.

Fluvoxamine but not citalopram increases serum melatonin in healthy subjects-- an indication that cytochrome P450 CYP1A2 and CYP2C19 hydroxylate melatonin.

Abstract: Objective: The nocturnal serum melatonin (MT) level increases after ingestion of fluvoxamine (FLU) – a selective serotonin re-uptake inhibitor (SSRI) with antidepressive properties. The mechanism behind the MT increase is unknown. Citalopram (CIT) is another SSRI. It is not known whether CIT affects the serum MT level. It may well be that these two compounds affect serum MT levels differently, inasmuch as the ways they inhibit cytochrome P 450 (CYP) enzymes in the liver differ markedly. FLU inhibits CYP1A2 potently, and to some extent also CYP2C19, whereas CIT is without such an effect. CYP enzymes are probably involved in the hepatic metabolism of MT. If FLU, but not CIT, inhibits liver enzymes involved in the metabolism of MT, different serum MT concentrations should probably ensue. The objective of this investigation was to test this hypothesis. Methods: Seven healthy subjects participated in three different experiments, which were performed in random order 6–8 days apart. In experiment A, placebo was given, in experiment B 40 mg CIT and in experiment C 50 mg FLU. All doses were given orally at 1600 hours. Serum MT concentrations were determined at regular intervals between 1600 hours and noon next day (20 h). Plasma concentrations of CIT were measured repeatedly in experiment B, and plasma FLU concentrations in experiment C. MT areas under the curve representing the 20-h period (MT-AUC0–20) were compared in the three experiments, and differences were statistically evaluated. Results: FLU augmented the MT-AUC0–20 by a factor of 2.8 compared with the effect of placebo (P < 0.01), whereas CIT was without significant effect. More MT was excreted in the urine after ingestion of FLU than after placebo. In contrast, CIT did not influence the MT excretion. A clear relationship was found between serum levels of MT and plasma concentrations of FLU. Conclusion: The serum MT level increased markedly after ingestion of FLU but not after CIT. The exact mechanism behind this finding is unknown, but decreased hepatic metabolism of MT by either CYP1A2 or CYP2C19, or both, is probable. Although exogenous MT, causing high MT concentration in plasma, has sleep-promoting properties in man, it is at this stage unknown whether serum MT concentrations in the range found in this study have similar effects. This has to be given further attention in additional studies.

Different versions of the anatomical therapeutic chemical classification system and the defined daily dose--are drug utilisation data comparable?

Abstract: Objective: To investigate whether published drug utilisation studies contain satisfactory references to the ATC/DDD version applied and thus are usable for comparative purposes. Methods and results: A literature survey of drug utilisation studies was made. Seventy-three articles were identified by two Medline searches, one in 1996 and another in 1998. The articles were classified into four different groups. Groups 1 and 2 give proper references to the defined daily doses (DDDs) used in the studies, either by full reference to the version of the ATC Index with DDDs or by listing the actual DDDs used. The articles in groups 1 and 2 represent 46% of the articles in the survey. The articles classified in groups 3 and 4 give references only to general articles about the anatomical therapeutic chemical classification (ATC)/DDD system or no references at all. Fifty-four percent of the articles in the survey were classified in these groups. In these articles it is not possible to identify which DDDs have been used in the presentation of drug consumption data. Conclusions: According to the results from our literature survey, it is not common practice to include the ATC codes and the DDD values used or to make reference to the versions of the ATC/DDD index used when results from drug utilisation studies are published. One possible reason for this might be little or no knowledge about the ATC/DDD system as a dynamic system in which alterations are made annually. The lack of references to the actual DDDs used in the studies make comparisons between different data sets difficult and misleading.

Potent mechanism-based inhibition of human CYP3A in vitro by amprenavir and ritonavir : comparison with ketoconazole

Abstract: Objective: Biotransformation of triazolam to its α-hydroxy and 4-hydroxy metabolites by human liver microsomes in vitro was used as an index of human cytochrome P 450 3A (CYP3A) activity Results: The reaction was strongly inhibited by co-incubation with the viral protease inhibitors ritonavir (IC50=014 μM) and amprenavir (IC50=25–29 μM), and by the azole derivative ketoconazole (IC50 = 007 μM) Pre-incubation of microsomes with ritonavir or amprenavir increased inhibitory potency (IC50 reduced to 007 μM and 14 μM, respectively) This was not the case with ketoconazole Conclusions: Thus, ritonavir and amprenavir are highly potent mechanism-based inhibitors of human CYP3A isoforms

Start of oral morphine to cancer patients: effective serum morphine concentrations and contribution from morphine-6-glucuronide to the analgesia produced by morphine.

Abstract: Objective: To investigate the serum concentrations of morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) and the relationships between serum concentrations and clinical effects associated with start of morphine treatment in cancer patients. Methods: Forty patients with malignant disease and intolerable pain on weak opioids (codeine/dextropropoxyphen) were included. After a wash-out period, titration with immediate-release (IR) morphine was started. When a stable dose was achieved, the morphine treatment was changed to slow-release (SR) morphine in equivalent daily dosages. Clinical data and serum concentrations of morphine, M3G and M6G were obtained at the end of the IR and SR morphine treatment periods. Results: The mean trough serum morphine concentration associated with pain relief was 66 nmol/l. The corresponding mean concentrations of M6G and M3G were 257 nmol/l and 1943 nmol/l, respectively. Morphine serum trough concentrations showed a 33-fold variation. Seventy percent of the variation was predicted in a model including age, daily morphine dose and M6G/morphine ratio as independent variables. No associations were observed between side effects and serum concentrations of morphine and its metabolites. Conclusion: In this study, a mean serum trough morphine concentration of 66 nmol/l was associated with satisfactory pain relief when disease progression required an increase in intensity of pain therapy from step II to step III in the World Health Organization pain ladder. An increased ratio of M6G to morphine serum concentrations predicted lower effective serum morphine concentrations at the time of satisfactory pain relief. This observation supports that M6G contributes to the pain control produced by oral morphine in patients with pain caused by malignant disease.

Site of nicotine absorption from a vapour inhaler--comparison with cigarette smoking.

Abstract: Objective: The aim of the study was to assess the site of nicotine absorption during and after use of a nicotine-vapour inhaler compared with that after cigarette smoking.

Antibiotic utilization at the university hospital after introducing an antibiotic policy

Abstract: Objective: Antibiotic formulary restrictions are among the most popular methods to control antibiotic utilization in hospitals. The aim of the present survey was to investigate the influence of “reserve antibiotic” on antimicrobial utilization at the University Hospital Center (UHC) Rijeka.

Frequency of daily over-the-counter drug use and potential clinically significant over-the-counter-prescription drug interactions in the Finnish adult population.

Abstract: Objective: To explore the frequency of continuous use of over-the-counter (OTC) drugs among the Finnish adult population and the potential for harmful interactions between OTC drugs and prescribed (Rx) drugs.

Drug use in pregnancy among Italian women.

Abstract: Objective: To describe the use of drugs among Italian women during pregnancy and to compare it with other reports in Italy from the last 10 years. Methods: A random sample of women who delivered in 1995–1996 were interviewed with regard to the care they received during pregnancy, delivery and the post-natal period. Information on antenatal care included maternal reports on the use of drugs during pregnancy. Results: Of the 9004 women interviewed, 75% took at least one drug during pregnancy. Users took a median number of two drugs. Iron (51%) and vitamins (25%) dominate prescriptions throughout pregnancy. Fifteen percent of women reported treatment for threatened abortion and 27% for risk of pre-term delivery. The data do not differ from the drug exposure profile during pregnancy reported in other Italian studies. Logistic regression analysis of drug use (excluding haematologicals and nutritionals) shows an increased risk of usage for older women, the better educated, for those who reported health problems and those who had compulsory bed rest and/or hospitalisation during pregnancy. Conclusion: Seventy-five percent of the women reported use of at least one drug during pregnancy. Haematological and nutritional drugs are over prescribed. Although hormones have been clearly proven to be ineffective in preventing threatened abortion, the study shows an almost unchanged and out of date prescription pattern of progestational drugs. In order to avoid unnecessary exposure to potential risk, maternity care procedures should be reviewed and strictly related to an “evidence-based” approach.

Effect of grapefruit juice on pharmacokinetics and pharmacodynamics of verapamil enantiomers in healthy volunteers.

Abstract: Objectives: To determine the effect of grapefruit juice on the pharmacokinetics and pharmacodynamics of S- and R-verapamil (given as racemates) at steady state. Methods: Nine healthy male volunteers followed a randomised cross-over study comprising two treatment periods. Pretreatments of 200 ml orange juice (control) or grapefruit juice twice daily for 5 days and 120 mg verapamil (orally) twice daily for 3 days were given. On the study day, the subjects received the morning dose of verapamil with either orange juice (control) or grapefruit juice. Plasma and urine samples were collected for measurement of S- and R-verapamil and the metabolites S- and R-norverapamil. Blood pressure (BP), heart rate (HR) and PR-interval were monitored. Results: During the grapefruit juice period, the steady-state peak and trough concentrations of S-verapamil were moderately increased (peak 41±25 ng ml–1 versus 26±13 ng ml–1, trough 14±7 ng ml–1 versus 12±6 ng ml–1, P=0.08). Grapefruit juice significantly increased the area under the plasma concentration–time curve during the 12-h dose interval (AUC0–12 h) of S-verapamil by 36% (292±146 ng h ml–1 versus 215±102 ng h ml–1, P=0.04). Similar results were obtained for peak and trough concentrations of R-verapamil. The AUC0–12 h of R-verapamil was increased by 28% (1022±412 ng h ml–1 versus 800±316 ng h ml–1, P=0.04). Elimination half-life and renal clearance of both S- and R-verapamil were not affected. Considerable inter-subject variability in interaction was shown. There were no significant differences in the pharmacodynamic parameters (BP, HR and PR-interval). Conclusions: The present study has demonstrated an interaction between verapamil and grapefruit juice, which is likely due to an inhibition of intestinal metabolism resulting in increased oral bioavailability.

The impact of the CYP2D6 and CYP2C19 genotypes on venlafaxine pharmacokinetics in a Japanese population.

Abstract: Objective: The cytochrome P 450 isozymes CYP2D6 and CYP2C19 exhibit genetic polymorphism in human, including a marked interethnic difference. As the functional status of the isozymes CYP2D6 and CYP2C19 have an impact on the pharmacokinetics of some antidepressants, we investigated whether the disposition of venlafaxine was affected by the CYP2D6 and CYP2C19 genotypes. Methods: Twenty-eight adult Japanese men in good health participated in this study. Genomic DNA was isolated from peripheral lymphocytes, and the CYP2D6 genotype was determined using polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) analysis and XbaI-RFLP analysis. Subjects were categorized into the following four groups: group 1 CYP2D6*10/*10; group 2 CYP2D6*1/*10 and *2/*10; group 3 CYP2D6*1/*1, *1/*2 and *2/*2; and group 4 the other genotypes. Two defective CYP2C19 alleles (CYP2C19*2 and CYP2C19*3) were identified by means of PCR-RFLP analysis. Venlafaxine was administered orally following an overnight fast. Plasma concentrations of venlafaxine and O-desmethylvenlafaxine were monitored using high-performance liquid chromatography up to 24 h. Results: The peak plasma concentration and values of area under the concentration–time curve up to 24 h for venlafaxine were 298% and 453% higher for group 1 than group 3, and 91% and 120% higher for group 2 than for group 3, respectively. The homozygote for two defective alleles of CYP2C19 showed a higher concentration of venlafaxine within group 1 and group 2. Conclusion: The CYP2D6*10 allele and two CYP2C19 defective alleles, common in an Asian population, are the most likely genetic factors to use in determining interindividual differences in the pharmacokinetics of venlafaxine, although the results with respect to CYP2C19 are preliminary because of the few subjects used.

CYP2D6 genotype and antipsychotic-induced extrapyramidal side effects in schizophrenic patients

Abstract: Objective: In order to evaluate whether poor metabolizers (PM) of debrisoquine are overrepresented among patients with acute dystonic reactions and chronic movement disorders associated with the administration of antipsychotic drugs, the CYP2D6 genotype was determined in schizophrenic patients. Methods: Allele status for CYP2D6*3, CYP2D6*4, CYP2D6*5, and CYP2D6*6 as well as gene duplication was determined by allele-specific PCR, long-PCR and restriction fragment length polymorphism analysis (RFLP) in 119 schizophrenic patients (99 males and 20 females). All subjects were treated with antipsychotics metabolized, at least partially, by this isozyme. Sixty-three of the patients (52.9%) had a history of extrapyramidal side effects (EPS), while 56 (47.1%) had not experienced such problems (controls). Results: Sixty-five patients (54.6%) were homozygous for a functional CYP2D6*1 allele, 44 (37.0%) were heterozygous for detrimental alleles, and 4 (3.4%), who carried two detrimental alleles, were classified as PM. In six patients (5.0%) duplication of a functional CYP2D6 gene was found, and they were consequently classified as ultrarapid metabolizers (UM). Homo- and heterozygous extensive metabolizers (EM) as well as UM were equally distributed between patients with and without EPS, whereas all the PM had a history of EPS. No significant differences in allele frequencies between the two groups were found. Conclusion: Although the results cannot be considered conclusive due to the small number of PM patients in our study, the PM genotype may be a predisposing factor for antipsychotic-induced EPS. Knowledge of the CYP2D6 genotype, before starting antipsychotic therapy, might be useful in identifying subjects at risk of developing EPS.

Ciprofloxacin increases serum clozapine and N-desmethylclozapine: a study in patients with schizophrenia

Abstract: Objective: A possible pharmacokinetic interaction between a CYP1A2 inhibitor, ciprofloxacin, and clozapine was studied in schizophrenia patients with stable clozapine treatment. Methods: A randomised double-blind cross-over study design with two phases was used. Seven schizophrenic inpatients volunteered to receive, in addition to their previous drug regimen, either 250 mg ciprofloxacin or placebo twice daily (b.i.d.) for 7 days. The phases were separated by a 7-day wash-out period. Serum concentrations of clozapine and its main metabolite N-desmethylclozapine were measured during both phases before the first dose on day 1 and on days 3 and 8. Results: Ciprofloxacin increased mean serum concentration of clozapine and N-desmethylclozapine by 29% (P<0.01) and 31% (P<0.05), respectively. There was a significant positive correlation (r=0.90, P<0.01) between the individual concentrations of serum ciprofloxacin and the increase in concentrations of clozapine plus N-desmethylclozapine. The increase in serum clozapine concentrations correlated significantly (r=0.89, P<0.01) with the ratios of N-desmethylclozapine to clozapine concentrations. Conclusion: Even a low dose of ciprofloxacin can moderately increase serum concentrations of clozapine and N-desmethylclozapine. A probable mechanism of interaction is an inhibition of CYP1A2 enzyme by ciprofloxacin. The possibility of clinically significant interaction should be considered, especially when higher doses of ciprofloxacin are used concomitantly with clozapine.

Circadian variation of the urinary 6β-hydroxycortisol to cortisol ratio that would reflect hepatic CYP3A activity

Abstract: Objectives: Chronopharmacokinetics of drugs metabolized by cytochrome P 450 3A (CYP3A) has been reported recently; however, little is studied on intra-individual circadian variation in CYP3A activity in human. The aim of this study was to assess the intra-individual diurnal variation and day-to-day variation of the urinary 6β-hydroxycortisol to cortisol ratio, a noninvasive index of human CYP3A activity. Methods: Urine samples from ten healthy Japanese men were collected over four time intervals (0900 hours to 1300 hours, 1300 hours to 1700 hours, 1700 hours to 2100 hours and 2100 hours to 0900 hours) on days 1, 5 and 14 to verify diurnal variation, and 24-h urine was collected to study day-to-day variation over 2 weeks. Urinary 6β-hydroxycortisol and cortisol were determined by means of high-performance liquid chromatography/atmospheric pressure chemical ionization–mass spectrometry. Results: The ratio of urinary 6β-hydroxycortisol to cortisol exhibited noteworthy diurnal variation intra-individually; 2.8-fold on average. However, day-do-day intra-individual variation of the ratio was not observed over 2 weeks; the coefficient of variation was 11.9 ± 3.0%. Conclusion: The result indicates that imprudent use of random urine has a great risk of false evaluation in assessment of the 6β-hydroxycortisol to cortisol ratio and that the ratio in 24-h urine samples provides a more robust measure of the inter-individual difference of this metabolic ratio, which to a certain but not complete extent represents the CYP3A activity.

Effect of three caffeine doses on plasma catecholamines and alertness during prolonged wakefulness.

Abstract: Objective: Determine the relationship between caffeine, catecholamines, and alertness during prolonged wakefulness. Methods: Following 49 h of prolonged wakefulness, each of 50 healthy males (18–32 years) orally ingested either a placebo or one of three doses of caffeine, 2.1 (low), 4.3 (medium), or 8.6 mg kg–1 body weight (high), in a randomized double-blind design. Wakefulness continued for an additional 12 h during which venous blood samples were collected for catecholamine and caffeine analysis [determined using high-performance liquid chromatography (HPLC)]. A sleep latency test, the Stanford sleepiness scale, and a choice reaction time test were administered periodically during the post-dosing period and served as measures of alertness (physiological, subjective, and behavioral, respectively). Results: Caffeine had no significant effect on noradrenaline, but adrenaline was significantly increased between 1 h and 4 h post-dosing in the high dose group compared with a placebo group. Following caffeine administration, responses to sleep latency, sleepiness scores, and reaction time scores showed dose-related changes that were exhibited by significant correlation coefficients. Conclusion: The results indicate that high doses of caffeine have a significant and beneficial effect on alertness during prolonged wakefulness.