Manual of pharmacologic calculations with computer programs

Common Brain Mechanisms of Chronic Pain and Addiction

Cannabis has been used for medicinal purposes for thousands of years. The prohibition of cannabis in the middle of the 20th century has arrested cannabis research. In recent years there is a growing debate about the use of cannabis for medical purposes. The term 'medical cannabis' refers to physician-recommended use of the cannabis plant and its components, called cannabinoids, to treat disease or improve symptoms. Chronic pain is the most commonly cited reason for using medical cannabis. Cannabinoids act via cannabinoid receptors, but they also affect the activities of many other receptors, ion channels and enzymes. Preclinical studies in animals using both pharmacological and genetic approaches have increased our understanding of the mechanisms of cannabinoid-induced analgesia and provided therapeutical strategies for treating pain in humans. The mechanisms of the analgesic effect of cannabinoids include inhibition of the release of neurotransmitters and neuropeptides from presynaptic nerve endings, modulation of postsynaptic neuron excitability, activation of descending inhibitory pain pathways, and reduction of neural inflammation. Recent meta-analyses of clinical trials that have examined the use of medical cannabis in chronic pain present a moderate amount of evidence that cannabis/cannabinoids exhibit analgesic activity, especially in neuropathic pain. The main limitations of these studies are short treatment duration, small numbers of patients, heterogeneous patient populations, examination of different cannabinoids, different doses, the use of different efficacy endpoints, as well as modest observable effects. Adverse effects in the short-term medical use of cannabis are generally mild to moderate, well tolerated and transient. However, there are scant data regarding the long-term safety of medical cannabis use. Larger well-designed studies of longer duration are mandatory to determine the long-term efficacy and long-term safety of cannabis/cannabinoids and to provide definitive answers to physicians and patients regarding the risk and benefits of its use in the treatment of pain. In conclusion, the evidence from current research supports the use of medical cannabis in the treatment of chronic pain in adults. Careful follow-up and monitoring of patients using cannabis/cannabinoids are mandatory.

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Cannabinoids and Pain: New Insights From Old Molecules

Magnesium has an established role in obstetrics and an evolving role in other clinical areas, in particular cardiology. Many of the effects involving magnesium are still a matter of controversy. Over the next decade, it is likely that improvements in the measurement of magnesium, a clearer understanding of the mechanisms of its actions and further results of clinical studies will help to elucidate its role, both in terms of treating deficiency and as a pharmacological agent.

Magnesium: Physiology and Pharmacology

Magnesium is well known for its diverse actions within the human body. From a neurological standpoint, magnesium plays an essential role in nerve transmission and neuromuscular conduction. It also functions in a protective role against excessive excitation that can lead to neuronal cell death (excitotoxicity), and has been implicated in multiple neurological disorders. Due to these important functions within the nervous system, magnesium is a mineral of intense interest for the potential prevention and treatment of neurological disorders. Current literature is reviewed for migraine, chronic pain, epilepsy, Alzheimer’s, Parkinson’s, and stroke, as well as the commonly comorbid conditions of anxiety and depression. Previous reviews and meta-analyses are used to set the scene for magnesium research across neurological conditions, while current research is reviewed in greater detail to update the literature and demonstrate the progress (or lack thereof) in the field. There is strong data to suggest a role for magnesium in migraine and depression, and emerging data to suggest a protective effect of magnesium for chronic pain, anxiety, and stroke. More research is needed on magnesium as an adjunct treatment in epilepsy, and to further clarify its role in Alzheimer’s and Parkinson’s. Overall, the mechanistic attributes of magnesium in neurological diseases connote the macromineral as a potential target for neurological disease prevention and treatment.

/pdf/the-role-of-magnesium-in-neurological-disorders-5a433htdhf.pdf

The Role of Magnesium in Neurological Disorders

Pain is a common symptom in older people. It is possible that pain is underreported in older persons due to an incorrect belief that it is an inevitable part of aging. Opioid analgesics are potent medications, with confirmed efficacy for the treatment of moderate to severe pain. These drugs are commonly used in older persons. However, there is insufficient evidence regarding safety of opioids in older patients. One of the reasons for this is the lack of randomized, controlled clinical trials. People of advanced age often have comorbidites and use other prescription drugs, as well as over-the-counter (OTC) compounds, thus making them more suceptible to the risk of interactions with opioids. Significant pharmacokinetic and pharmacodynamic changes that occur with advancing age increase the risk of adverse effects of opioids. There are also some discrepancies between guidelines, which recommend the use of lower doses of opioids in older patients, and the findings in the literature which suggest that pain is often undertreated in this age group. It seems that there are significant variations in the tolerability of different opioid analgesics in older people. Morphine, fentanyl, oxycodone, and buprenorphine are still the preferred evidence-based choices for add-on opioid therapy for these patients. However, the safety and efficacy of other opioids in older patients, especially if comorbidities and polypharmacy are present, is still questionable. This review addresses the most important aspects of the use of opioids in older persons, focusing on pharmacokinetics, pharmacodynamics, adverse effects, and interactions.

Pharmacotherapy of Pain in the Older Population: The Place of Opioids

Magnesium has been shown to produce an antinociceptive effect on animal models of neuropathic and inflammatory pain. It has also been shown to exert an analgesic effect on humans in conditions presenting acute (postoperative pain) and chronic (neuropathic) pain. As it is known that magnesium is a physiological antagonist of the N-methyl-Daspartate (NMDA) receptor ion channel, and that the NMDA receptor plays a key role in central sensitization, the primary mechanism through which magnesium produces its analgesic effect is believed to be blockade of the NMDA receptor in the spinal cord. In addition, magnesium blocks calcium channels and modulates potassium channels. The activation of the nitric oxide (NO) pathway could have an important role in the antinociceptive effects of systemic magnesium sulfate in the somatic, but not in the visceral model of inflammatory pain. Although it is known for some time that intramuscular, intravenous and subcutaneous injections of magnesium sulfate in humans, and intraperitoneal injection in rodents produce local pain sensation, the mechanism of this action was elucidated only recently. It was demonstrated that subcutaneous injection of an isotonic, pHadjusted (7.4) solution of magnesium sulfate (6.2%) to rats produces local peripheral pain via activation of peripheral TRPA1, TRPV1, TRPV4 and NMDA receptors and peripheral production of NO. In animal models of pain, magnesium has been shown to exert both antinociceptive and pronociceptive effects by acting on different ion channels and NO pathways, however, the precise mechanisms remain to be elucidated.

Magnesium in Pain Research: State of the Art.

Context: Magnesium and MK-801 (dizocilpine), antagonists of N-methyl-d-aspartate receptors, are involved in the processing of pain.Objective: This study determines whether magnesium sulfate (MS) and MK-801 affects visceral inflammatory pain and determines a possible mechanism of action.Materials and methods: Analgesic activity was assessed using the acetic acid-induced writhing test in rats. MS (1–45 mg/kg) or MK-801 (0.005–0.03 mg/kg) was administrated subcutaneously (s.c.). To assess possible mechanisms of action, we examined the effects of l-NAME (10 mg/kg, intraperitoneal), methylene blue (0.5 mg/kg, s.c.), and glibenclamide (3 mg/kg, s.c.) on the effect of MS or MK-801.Results: MS and MK-801 showed biphasic and linear dose–response pattern, respectively. MS reduces the number of writhing on the dose of 1, 5, and 15 mg/kg by 60, 50, and 78%, respectively, while it has no effects on the doses of 30 and 45 mg/kg. MK-801 (0.005–0.03 mg/kg) showed decrease in the number of writhing by 33–79%. The ...

https://www.tandfonline.com/doi/pdf/10.3109/13880209.2014.996821

The antinociceptive effects of magnesium sulfate and MK-801 in visceral inflammatory pain model: The role of NO/cGMP/K+ATP pathway

Objective Magnesium is an endogenous voltage-dependent NMDA receptor-channel blocker and ketamine is a non-competitive NMDA receptor antagonist. Magnesium may potentiate the effect of ketamine in analgesia and anaesthesia, but may also interact in an opposing manner. This study aimed at evaluating type of the interaction between magnesium sulphate and ketamine administered systemically in rats with an acute nociceptive pain (tail-immersion test). Materials and methods Analgesic activity was assessed by tail-immersion test in male Wistar rats (200-250 g). The distal 5 cm of the tail was immersed in a warm water bath (55 ± 0.5°C) and the time for tail-withdrawal was measured as response latency. Results Magnesium sulphate (2.5-30 mg/kg, s.c.) and ketamine (2.5-30 mg/kg, i.p.) administered alone did not produce any effect. However, significant antinociception (synergistic interaction) was revealed at the following doses of ketamine: magnesium sulphate of 5:5 mg/kg, 2.5:5 mg/kg and 10:5 mg/kg. The effect was not dose-dependent, and a greater response was obtained when ketamine was administered before magnesium sulphate. Conclusions This study revealed that (1) magnesium sulphate and ketamine given alone were not effective against acute nociceptive pain in rats, but (2) a combination of both drugs resulted in synergistically inhibited nociception, (3) which occurred only at selected low doses and proportions of the medications in a combination and (4) suggested the importance of the order of drug administration.

Dragana Srebro

Papers

Cannabinoids and Pain: New Insights From Old Molecules

Pharmacotherapy of Pain in the Older Population: The Place of Opioids

Magnesium in Pain Research: State of the Art.

The antinociceptive effects of magnesium sulfate and MK-801 in visceral inflammatory pain model: The role of NO/cGMP/K+ATP pathway

A synergistic interaction between magnesium sulphate and ketamine on the inhibition of acute nociception in rats