Lack of medication dose uniformity in commonly split tablets.

OBJECTIVE: To divide 11 commonly split tablets and evaluate the resulting half-tablets for content uniformity.
DESIGN: Pre-post comparison.
SETTING: Laboratory.
INTERVENTIONS: A trained individual split tablets of 11 products using a single-edged razor blade and 3 products by hand alone. MAIN OUTCOME MEASURES: The Uniformity of Dosage Units test published in the United States Pharmacopeia 24 (USP), which applies to whole tablets, was adapted liberally to assess the dose uniformity of the resulting split tablets.
RESULTS: Of the 11 razor-split products, 8 failed the liberal adaptation of the USP uniformity test. No visible tablet features (e.g., scoring) predisposed a product's split tablets to pass or fail the uniformity test. All three hand-split tablets failed the uniformity test and yielded worse results than did razor-split tablets.
CONCLUSION: The majority of the 11 drug products we tested, when assessed for their ability to be split into half-tablets of equal dose, failed a liberally interpreted USP uniformity test. The practice of dividing tablets to save costs or to improve a dosage regimen may not cause problems for patients using drugs with low toxicity and relatively flat dose-response relationships, but it is not recommended for patients using drugs with more substantial toxicity and steep dose-response efficacy curves.