The disposition of phenylbutazone (4.4 mg/kg), administered intravenously to six Welsh Mountain ponies, was described by a two-compartment open model. Pharmacokinetic parameters were not significantly different after morning dosing in comparison with afternoon dosing. When phenylbutazone (4.4 mg/kg) was administered orally to the same ponies, marked variations in time to peak concentrations were produced with different feeding schedules. When access to hay was permitted before and after dosing, the mean time to peak concentration was 13.2 +/- 1.2 h and double peaks in the plasma concentration-time curve were common. Double peaks were also encountered when phenylbutazone was given to ponies deprived of food prior to, and allowed access to hay after, dosing. In this circumstance, mean times to peak concentration were much shorter (3.8 +/- 1.3 h after morning dosing and 5.3 +/- 1.5 h followed afternoon dosing). Absorption was more regular and double peaks were less apparent when food was withheld both before and after dosing. In order to explain these findings, it is tentatively postulated that, whereas some of the administered dose of phenylbutazone may be absorbed quickly, some may become adsorbed on to the feed and subsequently released by fermentative digestion in the large intestine and/or caecum. The consequences of delayed absorption in fed animals for toxicity and clinical efficacy, and for the use of phenylbutazone in equestrian sports, are considered. Delayed absorption in ponies given access to hay was not accompanied by a significant reduction in total absorption. Bioavailability was estimated to be approximately 69% in fed and 78% in unfed ponies. Estimates of bioavailability gave similar values for morning (72%) and afternoon (71%) dosing.

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Prevalence of animal diseases is one of the major livestock production constraints in Kenya with high impacts on livelihoods due to related economic losses affecting food security in the country. The use of synthetic drugs for disease management has challenges. This makes the use of medicinal plants for treatment a rational alternative. Ascarids, Toxocara canis and Ancylostoma caninum are among the most frequently observed helminth parasites in dogs in Kenya. The two parasites are also known to cause helminthiasis in human beings. This study was designed to evaluate the in vitro efficacy of ethanol and aqueous extracts from bulbs of A. sativum and A. cepa and from leaves of J. curcas against T. canis and A. caninum parasites. Six (6) extracts from three (3) plants: A. cepa, A. sativum and J. curcas were selected for in vitro anthelmintic screening by measuring ability to inhibit hatching and development of eggs and survival of larvae in vitro. The ethanol extracts of A. cepa inhibited hatching of 100% of eggs of A. caninum between 10,000 and 2,500 ug/ml and 100% of eggs of T. canis between 10,000 and 1,250 ug/ml while that of A. sativum inhibited hatching of 100% of A. caninum eggs between 10,000 and 5,000 ug/ml. However the ethanol extract of A. sativum did not have the same effect on the development of T. canis eggs at these concentrations. The ethanol extracts of both A. cepa and A. sativum affected the survival of 100% of A. caninum larvae at a concentration of 156 ug/ml and above. The water extracts of the three plants had moderate effects on the eggs and the larvae of both parasites. The results indicate that the ethanol extracts of A. cepa and A. sativum have anthelmintic properties which should be investigated further to support the ethnoveterinary use of the plants as anthelmintics for control and treatment of worm infestation in dogs.

Summary Five matched pairs of horses were used to investigate the effects of phenylbutazone on a range of physiological, biochemical and haematological variables. The drug was given by mouth daily for 15 consecutive days at the manufacturer's recommended dose rates to one group of horses (Group A); the second group (Group B) received equivalent doses of a placebo. For some of the measured parameters, significant changes were recorded in both groups, indicating background instability. Significant decreases in serum total protein, albumin, plasma pH, viscosity and magnesium, and an increase in albumin: globulin ratio occurred in Group A, but not in Group B. These changes were, therefore, attributed to phenylbutazone or its metabolites. Toxicologically, the change in pH is probably unimportant but the decrease in protein concentration may have resulted from a protein losing enteropathy and/or from decreased synthesis in the liver. In one animal which received phenylbutazone, clinical signs of toxicity (lethargy, inappetance, oedema) were observed and evidence of hepatotoxicity and haematological changes were also noted in this horse. It is concluded that recommended dose rates of phenylbutazone should never be exceeded and that the period for which the highest dose (4.4 mg/kg body weight twice daily for four days) is administered should be reduced. In clinical cases, where phenylbutazone toxicity is suspected, measurement of serum or plasma protein concentration might provide an indication of the need to reduce dose levels or stop therapy. Résumé Cinq paires de chevaux comparables ont été utilisés pour rechercher les effets de la phénylbutazone sur un ensemble de variables physiologiques, biochimiques, hématologiques. Le médicament fut administréà un groupe de chevaux (Groupe A), par voie orale, chaque jour durant 15 jours consécutifs; on respectait les posologies recommandées par le fabricant. Un second groupe (Groupe B) recut dans les mêmes conditions un placebo. Pour quelques paramètres, des changements significatif furent constatés dans les deux groupes ce qui indique une instabilité des conditions fixes de l'expérience. Au sein du Groupe A, une diminution significative s̀e produisit pour les protéines totales, pour l'albumine, pour le pH plasmatique, pour la viscosité et pour le magnésium plasmatiques et une augmentation dans le rapport globuline albumines. Les modifications ne se produisirent point au sein du Groupe B. Les changements furent en conséquence attribués à la phénylbutazone ou a ses métabolites. Sur le plan toxicologique, la variation du pH est probablement sans importance; l'abaissement de la concentration en protéines peut résulter d'une entéropathie spoliatrice ou (et) d'une synthèse hépatique diminuée. Chez un animal recevant de la phénylbutazone, des signes cliniques de toxicité (léthargie, oedème et inappétence) furent observés; des signes d'hépatotoxicité et des sanguines furent remarqués chez ce cheval. On en conclue que les posologies recommandées pour la phénylbutazone ne devraient jamais...

Twenty laying birds were divided into four groups (n = 5) and given drinking water containing 0, 400, 600, and 800 mg/l of oxytetracycline respectively for 7 days. Eggs were collected continuously for 17 days after drug administration and stored at +4 degrees C. The oxytetracycline residues in yolk and albumen were analysed using a microbiological method with Bacillus cereus var. mycoides ATCC 11778 as the test organism. The mean maximum concentration of oxytetracycline was observed 2 days earlier in the albumen than in the yolk. The mean values in yolk and albumen were 0.526 and 0.280 mg/kg respectively. The depletion period was shorter for albumen than for yolk and oxytetracycline was detected in the yolk and albumen up to days 13 and 10 respectively. Withdrawal periods depended on the concentration of the antibiotic administered. Oxytetracycline residues reached a peak faster in albumen than in yolk, although the residues persisted for longer periods in the yolk.

Five pairs of matched horses were used to study the biochemical and haematological effects of a revised dosage schedule of phenylbutazone. One group of five horses received a phenylbutazone paste formulation daily for 12 days and a second group of five animals received a placebo preparation for a similar time. Some statistically significant differences were recorded from pretreatment levels in both groups of horses. These changes represented instability in baseline levels and could not be ascribed to phenylbutazone administration.

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