The oral 100-day LD50 index of phenacetin in guinea pigs

Abstract

The oral LD50 (100 days) of phenacetin in young, male guinea pigs (the daily intragastric dose which killed 50% of animals over a period of 100 days of administration) was 0.228 ± 0.081 g/kg/day. The oral 100-day LD50 index, or oral LD50 (100 days) expressed as a percentage of the acute, oral LD50 (1 dose), was 8.6 ± 3.1. At the oral LD50 (100 days) there occurred growth inhibition, increase in food and water intake and urinary volume, slowing of the respiratory rate, ataxia, dacryorrhea, loss of weight, some hydration of body tissues, extensive capillary-venous congestion, degenerative changes and infection of certain body organs. Part of the toxicity syndrome at the LD50 (100 days) was similar to that reported for several other chemical agents. Higher daily doses produced signs which approached those at the oral LD50 (1 dose). Compared with corresponding published data on other drugs, the results indicate that the oral 100-day LD50 index could be a useful single relative index of the effects of giving repeated large daily doses of drugs. Since the oral 100-day LD50 index of phenacetin in guinea pigs was lower than that in albino rats, species of animal would appear to be a factor in evaluating the significance of the index.