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Accuracy of Splitting of Carbamazepine Tablets Available in the Kenyan Market

Author: Odhiambo M.A. , Mwagiru P.M. , Mukindia G.
Is Part Of: Pharmaceutical Journal of Kenya, Volume 23, No. 2 (2017)
Carbamazepine is an example of a drug with a narrow therapeutic index (NTI) whose dose response should be carefully titrated to avoid adverse effects associated with over- or under-dosages. Currently, there are no studies in Kenya that have investigated the accuracy of splitting tablets of such drugs. Carbamazepine tablets available in Kenya are scored, indicating suitability for splitting.
This study set out to determine the uniformity in weight of half tablets of a number of brands of carbamazepine 200mg tablets, the loss in mass upon splitting, and the accuracy of splitting tablets by hand and by means of a knife.
Twenty tablets each of 5 different brands were split by hand and using a knife. The uniformity in weight of the halves obtained was compared as well as the accuracy of the splitting method.
It was found that none of the half tablets passed the adopted United States Pharmacopeia (USP) test for Uniformity in Weight, whether split by hand or using a knife. Eighty-seven (87%) half tablets obtained from splitting by hand passed the European Pharmacopeia (Ph. Eur.) test for Subdivision of Tablets while only 52 half tablets passed the USP test for Uniformity of Dosage Units. When tablets were split by means of a knife, 81 (81%) half tablets passed the Ph. Eur. test while only 34% of the half tablets passed the USP test. Loss in mass for majority of the products was less than 3%.
Splitting of tablets results in variations in weight of half tablets. The USP test is stricter compared to the Ph. Eur. Test with the majority of the half tablets satisfying the Ph. Eur. requirements. Splitting by hand gave better results than using a knife. However, due to weight variation of halves, splitting of carbamazepine tablets is not recommended.

Keywords: NTI - drugs, tablet splitting, half tablets, uniformity in weight, carbamazepine 200mg scored tablets
Publisher: The Pharmaceutical Society of Kenya
ISSN: 2411-6386