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Objective—To determine whether oral administration of metoclopramide or a commercially available powdered whole grapefruit (PWG) nutraceutical in combination with cyclosporine enhances systemic availability of cyclosporine in dogs.
Sample—8 healthy mixed-breed dogs in part 1 and 6 of these 8 dogs in part 2.
Procedures—Cyclosporine pharmacokinetics were determined over the course of 24 hours after oral administration of cyclosporine (5 mg/kg) alone, cyclosporine with metoclopramide (0.3 to 0.5 mg/kg), cyclosporine with 2 g of PWG, or cyclosporine combined with both metoclopramide and 2 g of PWG by use of a Latin square crossover study with a 14-day washout period between treatments. Sixty days later, 6 of the 8 dogs were given 10 g of PWG followed by cyclosporine, and pharmacokinetic parameters were compared with those previously obtained after administration of cyclosporine alone.
Results—Although metoclopramide or coadministration of metoclopramide and 2 g of PWG had no effect on the pharmacokinetic parameters of cyclosporine, compared with results for cyclosporine alone, the higher (10-g) dose of PWG resulted in 29% faster mean time to maximal plasma cyclosporine concentration, 54% larger area under the curve, and 38% lower apparent oral clearance.
Conclusions and Clinical Relevance—Adjustment of the cyclosporine dose may not be needed when metoclopramide is coadministered orally to prevent common adverse effects of cyclosporine. Powdered whole grapefruit has the potential to reduce the required orally administered dose of cyclosporine but only when PWG is used in an amount (at least 10 g) that is currently not cost-effective.
Dr. Cerundolo's present address is Dick White Referrals, Veterinary Specialist Centre, Station Farm, London Rd, Six Mile Bottom, Suffolk, CB8 0UH, England.
Dr. Shofer's present address is Department of Emergency Medicine, School of Medicine, University of North Carolina, Chapel Hill, NC 27599.
Dr. Radwanski was supported by an American College of Veterinary Dermatology Resident Research grant provided by Novartis. Dr. Court was supported by grant GM-061834 from the National Institute of General Medical Sciences, National Institutes of Health.
Presented in abstract form at the 24th North American Veterinary Dermatology Forum, Savannah, Ga, April 2009.
The authors thank Dr. Leslie M. Shaw, Dr. Michael C. Milone, JoAnn Gardiner, and Sam Miller for technical assistance.