Sulfadiazine pharmacokinetics

Another study (202) of sulfadiazine pharmacokinetics in carp treated by the intraperitoneal route showed an elimination half-life of 17.5 h at 20 C. Both acetylation and hydroxylation metabolic pathways appeared to occur, but they only represented 2% and 0.41 % of the dose, respectively. This is in strong contrast to the metabolism profile of sulfadiazine in mammals, where hydroxylation is much more important. 

When a single dose of radiolabeled sulfadiazine was administered to eels at 7 C (200), highest initial radioactivity was observed in blood, liver, kidney, and skin, with a tendency for accumulation in bile and skin. In another pharmacokinetic study (201) on sea-water rainbow trout fed a combination of sulfadia-zine-trimetlroprim, the elimination process for both sulfadiazine and trimethoprim rapidly reached a point at which only a small but persistent residue was left at 8 C as opposed to 10 C, sulfadiazine was the more potent residue promoter, still being detected at 90 days posttreatment. This was suggested to be a result of the greater binding ability of sulfadiazine as a weak electrolyte. The authors proposed a witlidrawal period for sulfadiazine-trimethoprim of 60 days at water temperatures above 10 C for tabled-size fish, and a prohibition on its use below 10 C for such fish. 

Based upon pharmacokinetic information and minimal inhibitory concentrations (MIC) for pyrimethamine, an oral daily dose of Img/kg in combination with 22 mg/kg sulfadiazine is recommended in horses. The duration of treatment is controversial and the recommendations range from a minimum of 3 months (least conservative) to the point at which the CSF is seronegative (most conservative). It is clear that the latter course of treatment is least likely to result in relapse of the clinical signs (Fenger 1997), but it is likely that this exceeds what is absolutely necessary in most cases. 

Shoaf S E. Schwark W S, Guard C L 1989 Pharmacokinetics of sulfadiazine/trimethoprim in neonatal male calves effect of age and penetration into cerebrospinal fluid. American Journal of Veterinary Research 50 396-402 Taylor W M, Simpson C F, Martin F G 1972 Certain aspects of toxicity of an amicarbalide formulation to ponies. American Journal of Veterinary Research 33 533-541 Watkins W M, Mosobo M 1993 Treatment of Plasmodium falciparium malaria with pyrimethamine and sulphadoxine a selective pressure for resistance is a function of long elimination half-life. Transactions of the Royal Society of Tropical Medicine and Hygiene 87 75-79... 

Example Silver sulfadiazine (Silvadene) Route Topical Pregnancy category C Pharmacokinetic Some absorbed PB UK ... 

A summary of the detailed information on the pharmacokinetics of sulfamethazine (also known as sulfadimidine) and sulfadiazine is provided by Papich and Riviere. ... 

Nouws JEM, Mevius D, Vree TB, Baakman M, Degen M, Pharmacokinetics, metabolism, and renal clearance of sulfadiazine, sulfamerazine, and sulfamethazine and of their N-4 acetyl and hydroxy metabolites in calves and cows, Am. J. Vet. Res. 1988 49 1059-1065. 

Nouws JEM, Vanginneken VJT, Grondel JL, Degen M, Pharmacokinetics of sulfadiazine and trimethoprim in carp... 

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