A fatal toxicity index (deaths per million National Health Service prescriptions) was calculated for antidepressant drugs on sale during the years 1975-84 in England, Wales, and Scotland. The tricyclic drugs introduced before 1970 had a higher index than the mean for all the drugs studied (p<0-001). In this group the toxicity of amitriptyline, dibenzepin, desipramine, and dothiepin was significantly higher, while that ofclomipramine, imipramine, iprindole, protriptyline, and trimipramine was lower. The monoamine oxidase inhibitors had intermediate toxicity, and the antidepressants introduced since 1973, considered as a group, had significantly lower toxicity than the mean (p<0-001). Ofthese newer drugs, maprotiline had a fatal toxicity index similar to that of the older tricyclic antidepressants, while the other newly introduced drugs had lower toxicity indices, with those for mianserin, nomifensine, trazodone, and viloxazine reaching significance. Provided that these drugs are equally effective clinically, serious consideration should be given to prescribing antidepressants with a lower fatal toxicity.

No abstract

Single dosages of DMEP (1,000-2,000 mg/kg), GMCH (50 mg/kg), ECH (25 and 50 mg/kg), FA (100 and 200 mg/kg), and MMS (100-400 mg/kg) were administered orally to 10 week old male Wistar rats. The rats were necropsied on the 11th day following dosing. The testes were weighed, homogenised and sonicated; numbers of sperm heads (total and abnormal) were counted and percentage sperm head abnormalities were calculated. Testes weights were significantly reduced only in rats exposed to 1,500 and 2,000 mg DMEP/kg. Compared with controls, there were significant increases in the incidence of abnormal sperm at all dose levels of MMS and the higher dose levels of DMEP (1,500 and 2,000 mg/kg), ECH and FA. No toxicologically significant effects upon total sperm counts were seen following the oral administration of any of the five chemicals tested. However, an additional group of rats given 100 mg MMS/kg intraperitoneally (i.p.) showed significant reductions in testes weight and total sperm head counts compared with control animals. It is concluded that this testicular sperm head counting technique is a useful tool in the detection of selective adverse effects of chemicals upon testicular sperm but requires further evaluation.

Hexamethyldisiloxane (HMDS) is a volatile linear siloxane dimer used in many applications, including precision cleaning, active ingredient carrier, and as a manufacturing intermediate. The purpose of this study was to characterize the subchronic vapor inhalation toxicity of the material as part of a comprehensive toxicology program. Groups of 20 male and 20 female Fischer 344 (F344) rats were exposed to nominal (and mean actual) vapor concentrations of 0, 50 (50), 200 (194), 600 (593), 1,500 (1,509) and 5,000 (5,012) ppm of HMDS, 6 hours per day, 5 days per week, for 13 weeks. No treatment-related signs of clinical toxicity or mortality, statistically significant effects upon body weight gain or food consumption, ophthalmoscopic changes, gross macroscopic necropsy findings, or organ weight changes were noted. Minor hematological, clinical biochemical, and urinalysis changes were seen but were not considered to be of toxicological relevance. Histological lesions in the kidney apparently consistent with male rat-specific alpha-2-urinary globulin nephropathy were observed in male rats exposed to 593, 1,509, and 5,012 ppm of HMDS, accompanied by slightly increased plasma urea and creatinine concentrations. No other treatment-related histological changes were seen in HMDS-exposed rats.

For 11 commonly used drugs, the n-octanol/water partition coefficient (pH 7.4 temperature 37 degrees C) and solubility in n-octanol were determined. The drugs tested were chlorpromazine, amitriptyline, trazodone, dextropropoxyphene, diltiazem, dibucaine, amethocaine, procaine, quinidine, acetylsalicylic acid and paracetamol. For eight of the drugs, the relative lipid saturation corresponding to a fatal plasma concentration was estimated from the two parameters determined above and the median fatal blood concentrations reported in the literature. For five of those eight drugs, the estimated relative saturation in the lipid phase fell within the range 0.001-0.004 which is close to relative saturation figures in aqueous and vapour phases already published for chemicals possessing a non-specific or physical mechanism of toxicity. Since this is determined largely by their lipid solubility, it is probable that accumulation in the lipid phase is an important determinant of the lethal toxicity of drugs and chemicals with a non-specific mechanism of toxicity.