Letters to the Editor: Effect of acetylsalicylic acid on foetal rats

The influence of diet on the toxicity of acetylsalicylic acid

The toxicity of acetylsalicylic acid in rats is greater when animals are fed a high carbohydrate diet than when they receive a high protein diet. Magnesium deficiency increases this difference, particularly in pregnant animals. The maximum B.P. human dose of acetylsalicylic acid is well tolerated by pregnant rats fed on the high protein diet but one quarter of this amount produced foetal resorption and deaths in rats fed on the high carbohydrate diet. Acetylsalicylic acid is not teratogenic under the conditions used and appears to be unlikely to be teratogenic in man since its dose-toxicity curve is steep. It appears essential to report the composition of the diet in toxicity tests.

Influence of protein malnutrition on teratogenicity of acetylsalicylic acid in rats

The effect of protein malnutrition (PM) on the embryotoxicity and teratogenicity of aspirin in rats has been studied. Protein malnourishment was produced from Days 7 to 21 of gestation by limiting the casein content of the diet to 5% in comparison to 20% for the normal animals. Six dose levels of aspirin (50-175 mg kg-1) were administered p.o. from Days 8 to 11 of pregnancy. Aspirin from 75 mg kg-1 d-1 induced growth retardation, embryolethality and teratogenicity, as shown by external, skeletal and visceral malformations. All these effects were potentiated by protein malnutrition.

NSAIDs: maternal and fetal considerations

Nonsteroidal anti-inflammatory drugs (NSAIDs) gained popularity in the late 1970s. Inhibition of prostaglandin synthesis with indomethacin has been reported to be effective for prevention of labor and for treatment for symptomatic polyhydramnios. Concern about its possible constrictive effect on the fetal ductus arteriosus has limited its use in pregnancy. Maternal indomethacin therapy has also been associated with reduction in urine production in the fetus and with oligohydramnios. Obstetricians have discouraged pregnant women from taking analgesic doses of aspirin, mainly because of the availability of paracetamol (acetaminophen), which causes less gastric irritation, but also because of fear of maternal and fetal hemorrhage and of possible premature closure of the ductus. These fears largely derive from studies on patients taking large doses and from extrapolation from other NSAIDs. The likelihood that treatment with 60-75 mg/day of aspirin markedly reduces the incidence of preeclampsia and fetal intrauterine growth retardation makes it important to reexamine its use. This review describes the pharmacology and pharmacokinetics of aspirin with particular reference to pregnancy and considers teratogenesis, prolongation of pregnancy and labor, maternal bleeding, fetal and neonatal bleeding, possible effects on the ductus arteriosus and pulmonary circulation, and possible nonspecific effects on intelligence and breast feeding and acute toxicity in the neonate.

Constant rate of infusion--improvement of tests for teratogenicity and embryotoxicity

Sodium salicylate was used as a model substance to investigate whether the embryotoxic effects on rat fetuses varies between two modes of administration. A marked increase in fetal adverse effects was observed at analgetic doses with the once-a-day bolus regimen compared to the constant rate input. The difference was less marked at antirheumatic levels.

Aspirin: teratogenic evaluation in the dog

Beagle bitches were administered aspirin at either 100 or 400 mg/kg/day between Days 15 and 22 or Days 23 and 30 postmating, and corresponding control groups were dosed with vehicle during one of these same time periods. Maternotoxicity was evident in all dogs dosed with 400 mg/kg/day of aspirin, but no signs of toxicity were observed when 400 mg/kg/day of aspirin was administered from Days 15 to 22 postmating. Teratogenicity, as evidenced by 50% malformation rate, was seen in fetuses from dams treated with 400 mg/kg/day on Days 23 to30 postmating. Observed malformations included, but were not limited to cleft palate,micrognathia, anasarca, cardiovascular malformations, and tial anomalies. No evidence of embryotoxic or teratogenic effects was seen in fetuses from either 100 mg/kg/day dosage level group. Examination of fetuses from 12 untreated litters and 4 vehicle-control litters revealed a very low spontaneous malformation rate confined almost entirely to minor tail abnormalities. These data support use of the dog as an acceptable alternative species in teratogenic screening.

Anti-fertility effect of non-steroidal anti-inflammatory drugs

The anti-fertility activity of prostaglandin synthesis inhibitors namely the non-steroidal anti-inflammatory drugs: acetyl salicylic acid, indomethacin and oxyphenbutazone were investigated in male and female albino rats and female albino rabbits. Oxyphenbutazone and indomethacin affected the reproductive process in male rats. Indomethacin 3 mg/kg. and acetyl salicylic acid 300 mg/kg produced significant anti-ovulatory activity in the rabbit. In female rats, all three drugs given in high doses over a period of two oestrous cycles reduced mating significantly, while only indomethacin given in a low dose of 0.8 mg/kg over a period of six oestrous cycles could reduce mating significantly. Anti-implantation activity was seen with indomethacin 4 mg/kg. alone, and though post-implantation activity was seen with all three drugs, it was associated with maternal deaths. It appears that non-steroidal anti-inflammatory drugs affect reproduction in female animals.