The protocol recommended for the micronucleus assay in mammalian bone marrow has been revised and simplified. The number of sample times has been reduced to one or two, depending upon the dosing protocol. The minimum number of cells to be scored per treatment group has been increased to 20,000 to increase the ability of the assay to detect a doubling of the control micronucleus frequency. Use of both male and female animals is recommended. Scoring of micronuclei in polychromatic erythrocytes of peripheral blood is included as a variation of the bone marrow assay. Published data on chemicals tested by the micronucleus assay have been reviewed and are summarized.

The in vivo micronucleus assay in mammalian bone marrow and peripheral blood. A report of the U.S. Environmental Protection Agency Gene-Tox Program

Data from animal teratology studies were surveyed to determine whether embryo-fetal mortality and fetal malformations result from a primary action of the agent on the conceptus or if they are secondary to maternal toxicity–a consequence of administration with high dose levels of test chemicals. A fairly strong association between embryo-fetal mortality and maternal toxicity was revealed by analysis of data from hamsters, mice, rats, and rabbits in 234 studies of chemical and physical agents, of which 83 were conducted at both maternotoxic and nonmaternotoxic doses, 94 only at maternotoxic doses, and 49 at nonmaternotoxic doses. In the above studies, only nine chemicals (four each in hamsters and rabbits and one in rats) were reported to induce embryo-fetal deaths at apparently nonmaternotoxic doses. These findings tend to suggest a contributory role for maternal toxicity in the induction of embryo-fetal deaths. The previously reported hypothesis that certain fetal defects in mice may perhaps be caused by maternal toxicity was also found to be true in a review of data on hamsters, rats, and rabbits. Salient maternal toxicity-associated fetal malformations were exencephaly, encephalocele, micro- or anophalmia, and fused ribs in hamsters and defective (fused, missing, or extra) ribs, vertebrae, and sternebrae, ex-, an-, or microphthalmia, and cleft palate in rats and rabbits. These malformations occurred at low frequencies, generally with no readily apparent dose-response relationship. Presumptive evidence indicates that embryo-fetal deaths, and the above-mentioned fetal malformations in experimental animals, which in published literature are presently attributed to chemical induction for a large number of chemicals, may be a consequence of maternal toxicity per se.

Maternal toxicity: A possible etiological factor in embryo‐fetal deaths and fetal malformations of rodent‐rabbit species

Trazodone is a triazolopyridine derivative with antidepressant activity, that is chemically unrelated to other currently available antidepressants. Its pharmacological properties differ from those of most other antidepressants. Trazodone exhibits antiserotonin activity in animal studies, but its mechanism of action in depressive illness in humans is not clear. It has an overall therapeutic efficacy comparable with imipramine and amitriptyline in depressive illness but, at dosages which have achieved a similar overall clinical improvement, trazodone causes fewer anticholinergic side effects than the tricyclic antidepressants. Trazodone appears also to have activity against the concomitant anxiety in depressed patients and in limited studies was comparable with diazepam and chlordiazepoxide in anxiety neurosis. Trazodone has been reported to be of value in tremors and chronic alcoholism. Studies in animals, limited human studies and the low incidence of cardiovascular side effects in controlled therapeutic trials, suggest that trazodone is less likely than imipramine to cause cardiotoxicity at therapeutic doses, but the effects of overdosage are not known at present. Trazodone appears to be well tolerated by the elderly, seldom aggravates psychotic symptoms and does not produce neurological side effects.

Trazodone: A Review of its Pharmacological Properties and Therapeutic Use in Depression and Anxiety

Developmental and reproductive toxicity (DART) end points are important hazard end points that need to be addressed in the risk assessment of chemicals to determine whether or not they are the critical effects in the overall risk assessment. These hazard end points are difficult to predict using current in silico tools because of the diversity of mechanisms of action that elicit DART effects and the potential for narrow windows of vulnerability. DART end points have been projected to consume the majority of animals used for compliance with REACH; thus, additional nonanimal predictive tools are urgently needed. This article presents an empirically based decision tree for determining whether or not a chemical has receptor-binding properties and structural features that are consistent with chemical structures known to have toxicity for DART end points. The decision tree is based on a detailed review of 716 chemicals (664 positive, 16 negative, and 36 with insufficient data) that have DART end-point data and ...

Framework for Identifying Chemicals with Structural Features Associated with the Potential to Act as Developmental or Reproductive Toxicants

The authors review four "second generation" antidepressants (maprotiline, amoxapine, trazodone, and nomifensine) in terms of action on biogenic amines and receptors, antidepressive efficacy, and adverse effects. Doxepin is used as a comparative agent and is similar to the prototypical tricyclic agents in all the above categories. Maprotiline is a selective noradrenergic agent, but shares a similar adverse effect profile with doxepin and may be associated with a high frequency of seizures in overdose. Amoxapine is a mixed action antidepressant with significant neuroleptic activity in vivo. Its adverse effect profile is highlighted by symptoms related to its neuroleptic activity, and seizures and acute renal failure in overdose. Trazodone is a selective serotonergic agent with low anticholinergic activity, and minimal morbidity/mortality in overdose. Reports of priapism, leading to impotence in some men, however, is of concern. Nomifensine is a potent noradrenergic and dopaminergic agent with low anticholinergic activity, and minimum cardiotoxicity and low morbidity/mortality in overdose. Its most important adverse effects include overstimulation and infrequent, usually reversible, immunologic hypersensitivity reactions. Trazodone and nomifensine have favorable profiles for use in the elderly. Trazodone may be more favorable in the anxious/agitated patient due to its sedative effects, whereas nomifensine may be more beneficial in the retarded, apathetic patient.

Second generation antidepressants: a comparative review.

A liquid pharmaceutical dosage form consisting of a solution comprising at least 10 % (w/v) of paracetamol in anhydrous PEG-200.

Liquid pharmaceutical composition based on paracetamol

Teratological study of etoperidone in the rat and rabbit.

The anticonvulsant drug phenytoin (DPH) has been suspected to produce embryotoxicity through an arene oxide intermediate. This drug was also found to be a genotoxic agent. These hypotheses were tested in pregnant mice modulating the phases I and II metabolizing enzymes. DPH was studied by assessing embryotoxicity, teratogenicity, and genotoxicity, the latter by the micronucleus test on the polychromatic erythrocytes of dams and fetuses.



DPH embryotoxicity was potentiated by inhibiting both cytochrome P-450 and epoxide hydrase and decreased by inducing cytochrome P-450. Equivocal results were obtained by modulating cytochrome P-448. The main DPH metabolite, p-hydroyphenytoin (HPPH), was ineffective both per se and after cytochrome induction or epoxide hydrase inhibition.



DPH did not exert genotoxicity on the maternal organism, no matter which modulating agent was used. In the fetus, however, weak genotoxic effects were observed. These effects significantly increased with inhibition of epoxide hydrase; they disappeared with induction of both cytochromes P-448 and P-450 or with inhibition of the latter. No genotoxicity was exerted by HPPH, even when the enzymatic pattern was modulated.



It is concluded that the major role in DPH embryotoxicity is played by the unchanged drug, while the presence of the arene oxide is determinant for genotoxic effects.

Correlations between embryotoxic and genotoxic effects of phenytoin in mice.

Acute Cardiovascular toxicity of trazodone, etoperidone and imipramine in rats☆

Lonidiamine is a novel indazole-carboxylic acid with antitumour properties; it has been studied for potential mutagenicity in a comprehensive battery of tests. In assays for the induction of gene mutations in prokaryotes (Ames test) and eukaryotes (induction of HPRT mutations in CHO cells), negative results were obtained. There was no evidence of the induction of chromosomal damage in cultured mammalian cells in vitro. No mutagenic activity was observed in tests for chromosomal damage in vivo, in somatic cells (micronucleus test) or in germinal cells (dominant lethal test). These negative results are consistent with observations indicating that lonidamine affects cellular energy processes, rather than the mechanisms of cell division. The lack of mutagenic properties suggests that lonidamine may present significant advantages in treatment of some tumours, offering a reduced risk of resistant clones, secondary cancer and heritable genetic damage.

Alberto Campana

Papers

Liquid pharmaceutical composition based on paracetamol

Teratological study of etoperidone in the rat and rabbit.

Correlations between embryotoxic and genotoxic effects of phenytoin in mice.

Acute Cardiovascular toxicity of trazodone, etoperidone and imipramine in rats☆

Lonidamine: a non-mutagenic antitumor agent