Research
Weight Variability of Pharmacist-Dispensed Split Tablets

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Objective

To determine the level of weight uniformity of fragments from tablets split into halves and dispensed by pharmacists.

Design

Pre-post comparison.

Setting

Laboratory analysis of split tablets returned unused from four long-term care facilities.

Interventions

Twenty-two dispensed prescriptions containing 560 split tablet halves were collected, and fragment weights (FWs) were determined. Theoretical weights (TWs) of split tablets of the same medications were determined mathematically.

Main Outcome Measures

Comparison of the mean FW with the mean TW of each dispensed prescription and determination of whether fragments met United States Pharmacopeia 24 (USP) criteria for weight variation of whole tablets.

Results

A significant difference (P < .05) between mean TW and mean FW was found in 2 (9.1%) of the 22 dispensed prescriptions. Overall, 30 (5.4%) of 560 fragments, contained in 10 (45.5%) of the 22 dispensed prescriptions, had weights that deviated by more than 15% from the mean FW. Of the 560 fragments, 32 (5.7%), contained in 10 (45.5%) of 22 dispensed prescriptions, had weights that deviated by more than 15% from mean TW. A total of 15 (68.2%) of the 22 dispensed prescriptions had standard deviations (SDs) that were more than 6% of the mean FW. None of the TWs displayed an SD greater than the USP limit of 6%. Only 7 (31.8%) of the 22 dispensed prescriptions met USP standards, with FWs not exceeding 15% of mean FW and SDs of no greater than 6%.

Conclusion

Tablet splitting resulted in an unacceptably high incidence of weight variation. Standards should be developed to ensure uniformity of split tablets.

Section snippets

Objective

The purpose of this study was to determine the level of weight uniformity of split-tablet fragments that were dispensed by pharmacists.

Methods

Pharmacist-dispensed split-tablet samples were obtained from four long-term care facilities (LTCFs) in the New York City metropolitan area to which we provide consulting pharmacy services. The samples were collected from discontinued medications. These LTCFs obtained their prescription medications from three off-site pharmacies, each of which delivers medications twice daily to each facility. Collectively, these pharmacies provide medications to more than 100 LTCFs.

Twenty-two discontinued

Results

Table 3 lists the means and SDs of the TWs and FWs of the 22 different dispensed prescriptions. Statistically significant differences between these mean weights were found for 2 (9.1 %) of the 22 medications evaluated, doxazosin (Cardura—Roerig; Pfizer) 2 mg and venlafaxine (Effexor—Wyeth) 25 mg.

Table 4 shows that, overall, 30 (5.4%) of the 560 tablet fragments, contained in 10 (45.5%) of the 22 dispensed prescriptions, had weights that deviated by more than 15% from the mean FW. Overall, 32

Discussion

Tablet splitting has been the subject of debates focusing on issues of adherence and accuracy. Most recently, the National Association of Boards of Pharmacy approved a resolution opposing mandated tablet-splitting practices.12 Similarly, the American Pharmaceutical Association's position is that mandatory tablet splitting is bad practice.13 Likewise, the American Society of Consultant Pharmacists strongly opposes mandating tablet splitting by patients. This opposition stems from concerns about

Limitations

This investigation had several limitations. First, no established criteria exist for weight uniformity of tablet fragments created by pharmacists or patients. The criteria we applied to the samples were established to assure dosage uniformity of intact dosage units, not fragments. It is only for lack of other established guidelines that these criteria were applied in this study. If tablet splitting is considered extemporaneous compounding, an even stricter weight variation standard would be

Conclusion

In our study, only 7 (31.8%) of the 22 dispensed prescriptions met USP standards, with FWs not exceeding 15% of mean FW and SDs of no greater than 6%. This variance is unacceptable in terms of the usual standards for uniformity of dosage forms and of extemporaneously prepared pharmacy products.

Manufacturers should be encouraged to review pricing policies for various product strengths and to offer additional strengths of medications that meet the needs of all patients, especially pediatric and

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The authors declare no financial interests or conflicts of interests in any product or service mentioned in this article, including grants, employment, gifts, stock holdings, and honoraria.

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