Alternative anticonvulsant drugs for dogs with seizure disorders - Veterinary Medicine
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Alternative anticonvulsant drugs for dogs with seizure disorders
People with seizure disorders have many drug options, but are there safe and effective alternatives to phenobarbital and bromide in dogs? These clinicians share their knowledge of the most promising new drugs.


VETERINARY MEDICINE


Miscellaneous anticonvulsant drugs

Several relatively new anticonvulsants used for seizure disorders in people have been suggested as potential alternatives in dogs. These drugs include lamotrigine, oxcarbazepine, tiagabine, and topiramate. Information about using these drugs in dogs with seizure disorders is limited to nonexistent. However, given the drugs' short half-lives in dogs and their expense, they will probably not prove useful in dogs. In addition to having a half-life in dogs of only two or three hours, lamotrigine undergoes significant hepatic metabolism in this species to a potentially cardiotoxic compound.10 Oxcarbazepine is thought to induce its own hepatic metabolism in dogs and has been demonstrated to have only a one-hour half-life after eight days of repeated oral dosing.38 Tiagabine has a half-life of about two hours in dogs and causes marked sedation and visual impairment in dogs at relatively low doses.39 The half-life of topiramate in dogs is only two to four hours.40

Curtis W. Dewey, DVM, MS, DACVIM (neurology), DACVS
Georgina Barone, DVM, DACVIM (neurology)
Kerry Smith, DVM
Department of Neurology and Neurosurgery
Long Island Veterinary Specialists
163 S. Service Road
Plainview, NY 11803

Gregg D. Kortz, DVM, DACVIM (neurology)
California Veterinary Neurology and Neurosurgery Specialists
1100 Atlantic St.
Roseville, CA 95678

REFERENCES

1. Thomas, W.B.: Seizures and narcolepsy. A Practical Guide to Canine and Feline Neurology (C.W. Dewey, ed.). Iowa State Press, Ames, 2003; pp 193-212.

2. Boothe, D.M.: Anticonvulsants and other neurologic therapies in small animals. Small Animal Clinical Pharmacology and Therapeutics (D.M. Boothe, ed.). W.B. Saunders, Philadelphia, Pa., 2001; pp 431-456.

3. Podell, M.: Strategies of antiepileptic drug therapy. Proc. ACVIM, ACVIM, Denver, Colo., 2001; pp 430-432.

4. Forrester, S.D. et al.: Disposition of clorazepate in dogs after single- and multiple-dose oral administration. AJVR 51 (12):2001-2005; 1990.

5. Forrester, S.D. et al.: Effects of a 44-day administration of phenobarbital on disposition of clorazepate in dogs. AJVR 54 (7):1136-1138; 1993.

6. Brown, S.A.; Forrester, S.D.: Serum disposition of oral clorazepate from regular-release and sustained-delivery tablets in dogs. J. Vet. Pharmacol. Ther. 14 (4):426-429; 1991.

7. Scherkl, R. et al.: Clorazepate in dogs: Tolerance to the anticonvulsant effect and signs of physical dependence. Epilepsy Res. 3 (2):144-150; 1989.

8. Podell, M.: Antiepileptic drug therapy. Clin. Tech. Small Anim. Pract. 13 (3):185-192; 1998.

9. Palmer, K.J.; McTavish, D.: Felbamate: A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in epilepsy. Drugs 45 (6):1041-1065; 1993.

10. Sisson, A.: Current experiences with anticonvulsants in dogs and cats. Proc. ACVIM, ACVIM, Lake Buena Vista, Fla., 1997; pp 596-598.

11. Rho, J.M. et al.: Mechanism of action of the anticonvulsant felbamate: Opposing effects on N-methyl-D-aspartate and gamma-aminobutyric acidA receptors. Ann. Neurol. 35 (2):229-234; 1994.

12. Yang, J.T. et al.: Felbamate metabolism in the rat, rabbit, and dog. Drug Metab. Dispos. 19 (6):1126-1134; 1991.

13. Adusumalli, V.E. et al.: Pharmacokinetics of felbamate in pediatric and adult beagle dogs. Epilepsia 33 (5):955-960; 1992.

14. Yang, J.T. et al.: Felbamate metabolism in pediatric and adult beagle dogs. Drug Metab. Dispos. 20 (1):84-88; 1992.

15. McGee, J.H. et al.: Acute, subchronic, and chronic toxicity studies with felbamate, 2-phenyl-1,3-propanediol dicarbamate. Toxicol. Sci. 45 (2):225-232; 1998.


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