Effect of Sulphadimidine on the Toxicity of Phenobarbital in Cockerels of Different Ages

Simunek J., Eva Hegerova, Jaroslava Klimeliova and Radka Zavadilova: Effect of Sulphadimidine on the Toxicity of Phenobarbital in Cockerels of Different Ages. Acta vet. Brno, 54,1985 : 183-187. Acute toxicity (LD50) of phenobarbital sodium salt administered intramuscularly alone and after premedication with sulphadimidine sodium salt (in i. m. doses of 0.2 gjkg body mass) given 15 or 120 minutes before phenobarbital administration was determined in cockerels aged 7,28 and 49 days. The acute toxicity of phenobarbital decreased with increasing age of the birds. Sulphadimidine premedication did not affect the acute phenobarbital toxicity in 7-day-old cockerels and increased it in 28and 59-day-old birds, compared to their non-premedicated counterparts, particularly when given 15 minutes before phenobarbital administration. In 28-day-old cockerels this rise in toxicity was significant. Observations for signs of depression within 24 hours of phenobarbital administration showed differences between the birds of the three different ages. The signs were most intense in the oldest birds and particularly in those premedicated with sulphadimidine 15 minutes before phenobarbital administration. Gallus domesticus, LD50 of phenobarbital, sulphadimidine premedication, age-dependence. With increasing use of biologically active substances under modern animal production conditions the question of interactions of these substances has been gaining in importance also in veterinary care. The problem is no longer just one of interactions between drugs typical pharmaceutical agents but may also involve interactions of other chemical substances used to influence physiological functions of farm animals (in growth promotion, oestrus synchronization, etc.). It can therefore be expected that, unlike in the past, drugs administered for therapeutical purposes nowadays will not exert their effects on animals having no previous medication with chemical substances or long-term drug treatment but will be given to animals already affected by some other exogenous biologically active substance(s). In the light of these considerations it is quite obvious that a large number of interactions may occur at all levels of drug action on the animal body, i.e. from the primary (pharmaceutical) phase where the pharmaceutical availability of active ingredient may be affected, over the pharmacokinetic phase with possible effects on the biological availability of active ingredient, to the pharmacodynamic phase where the effect proper of active ingredient may be affected in the process of its interaction with the corresponding receptor (Simunek 1980 a.o.). The experimental work reported here was focused on one item relevant to the aforementioned problem, namely interactions of phenobarbital with sulphadimidine in view of their possible effect on phenobarbital toxicity. Phenobarbital is the active ingredient of SedophenR, a drug for veterinary use, which contains in addition ascorbic acid and is used to tranquilize chickens (List of Veterinary Drugs SPOFA 1983). Sulphadimidine has been die most widely used sulphonamide in the therapy of coccidiosis of chickens in our country (Vodrazka et al. 1980 a.o; List of Veterinary Drugs SPOFA 1983). Simultaneous action of the two drugs in poultry appears therefore quite possible in the field. Moreover, phenobarbital is one of substances modifying the action of a number of biologically active substances, particularly by induction of biotransformation enzymes (K v etina and Fen dr i ch 1978 a.o.).