Prescribing - Donkey

Prescribing for donkeys

Pharmacokinetic differences have been demonstrated between horses and donkeys for a number of drugs e.g. oxytetracycline (Horspool et al, 1990), trimethoprim-sulfamethoxazole (Peck et al, 2002), phenylbutazone (Mealey et al, 1997, Matthews et al, 2001), flunixin meglumine (Coakley et al, 1999), and guaifenesin (Matthews et al, 1997) with, in general, Vd being lower, CL being higher and/or t½ being shorter in donkeys than in horses. These differences are of potential clinical significance for some, but not all, drugs that undergo hepatic biotransformation (Peck et al, 1997). The NSAID carprofen is apparently metabolised more slowly in donkeys than in horses (Mealey 'et al, 2004).

Dose rates and/or dosing regimens should not be altered unless there is sufficient evidence, based on controlled studies or best practice guidelines, for a particular drug. The dose rates cited in this chapter are based either on published literature or on the recommendations made by The Donkey Sanctuary (Trawford, 2004).

Most commonly, there is no approved product for use in the donkey. In the EU, equines are considered food-producing animals with the consequent implications in terms of what drugs can be administered and withdrawal periods. Donkeys are frequently kept as companion or leisure animals and are not usually intended for human consumption. Legislation has been put in place in the EU that covers equines of this type (Trawford, 2004). The range of medicines that can be used in the latter group can then be based on the so-called prescribing cascade (Bishop, 2001). In the absence of a veterinary product with market authorisation for use in donkeys, a veterinary product approved for use in the horse should be selected and used at the approved dose rate and regime.

Drug administration

The parenteral (e.g. intravenous, intramuscular, subcutaneous, intra-articular) or oral routes are used most commonly to administer drugs to donkeys. The choice of administration route depends on a number of factors, such as the need for dose titration and the expected onset and duration of action (see Table 1). Aseptic technique needs to be strictly practised for intra-articular administration since the consequences of intra-articular sepsis are particularly severe. Drugs can also be applied topically for local effects. However systemic action can occur following the administration of drugs by this route, e.g. atropine has systemic effects following ophthalmic administration.

References

• Horspool, L. (2008) Clinical pharmacology In Svendsen, E.D., Duncan, J. and Hadrill, D. (2008) The Professional Handbook of the Donkey, 4th edition, Whittet Books, Chapter 12

• Bishop, Y. (2000). ‘Code of Practice on Medicines’. Veterinary Formulary. 5th edition. Y. Bishop (ed). The Pharmaceutical Press, London. pp 5-8.
• Coakley, M., Peck, K.E., Taylor, T.S., Matthews, N.S., and Mealey, K.L. (1999). ‘Pharmacokinetics of flunixin meglumine in donkeys, mules and horses’. American Journal of Veterinary Research 60. pp 1441-1444.
• Horspool, L.J.I., McKellar, Q.A. (1990). ‘Disposition of oxytetracycline in horses, ponies and donkeys after intravenous administration’. Equine Veterinary Journal 22(4). pp 284-285.
• Matthews, N.S., Peck, K.E., Mealey, K.L., Taylor, T.S., and Ray, A.C. (1997). ‘Pharmacokinetics and cardiopulmonary effects of guaifenesin in donkeys’. Journal of Veterinary Pharmacology and Therapeutics 20. pp 442-226.
• Matthews, N.S., Peck, K.E., Taylor, T.S., and Mealey, K.L. (2001). ‘Pharmacokinetics of phenylbutazone and its metabolite oxyphenbutazone in miniature donkeys’. American Journal of Veterinry Research 62. pp 673-675.
• Mealey, K.L., Matthews, N.S., Peck, K.E., Burchfield, M.I., Bennett, B.S. and Taylor, T.S. (2004). ‘Pharmacokinetics of R(-) and S(+) carprofen after administration of racemic carprofen in donkeys and horses’. American Journal of Veterinary Research 65. pp 1479-1482.
• Mealey, K.L., Matthews, N.S., Peck, K.E., Ray, A.C., and Taylor, T.S. (1997). ‘Comparative pharmacokinetics of phenylbutazone and its metabolite oxyphenbutazone in clinically normal horses and donkeys’. American Journal of Veterinary Research 58. pp 53-55.
• Peck, K., Mealey, K.L., Matthews, N.S., and Taylor, T.S. (1997). ‘Comparative pharmacokinetics of caffeine and three metabolites in clinically normal horses and donkeys’. American Journal of Veterinary Research 58. pp 881-884.
• Peck, K.E., Matthews, N.S., Taylor, T.S., and Mealey, K.L. (2002). ‘Pharmacokinetics of sulfamethoxazole and trimethoprim in donkeys, mules, and horses’. American Journal of Veterinary Research 63. pp 349-353.
• Trawford, A.F. (2004). ‘Prescribing for donkeys’. The Veterinary Formulary. 6th edition. Y. Bishop (ed). The Pharmaceutical Press, London.

PHARMACOLOGY - DONKEY