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Tablet Splitting—Only If You “Half” To.
P roblem: Nearly all oral medications are sold in the dosage strengths that are most commonly prescribed for patients. Occasionally, the exact dose might not be available commercially, so more than one tablet or just part of a tablet may be needed. Although using more than one tablet for a single dose is customary, tablet splitting has become more commonplace for several reasons:
An article from a Veterans Affairs (VA) newsletter 2 and an article on the American Society of Consultant Pharmacists Web site 1 discuss the pitfalls associated with splitting tablets and suggest that this method is not the safest option if the patient-specific dose is available commercially.
Patient factors. Patients can easily become confused about the correct dose. Here is one example.
A woman was admitted to the hospital with unstable angina and hypertension. Her physician found that she had been taking the wrong dose of lisinopril (Prinivil, Merck; Zestril, AstraZeneca). She was supposed to be taking 5 mg twice daily, but the prescription label listed 10-mg tablets in the bottle. When the physician looked inside, he saw both pink and peach tablets, some split in half. Initially, the patient had been taking a 20-mg tablet twice daily. When the physician lowered the dose to 10 mg twice daily, the new prescription was filled. The patient then cut the leftover 20-mg tablets in half and put them in the same bottle that held the 10-mg tablets.
Later, the physician lowered the dose to 5 mg twice daily. Instead of filling the new prescription for 5-mg tablets, she tried to find all the 10-mg tablets to split them in half, but some remained whole. In this case, no one could be certain of the dose the patient had been taking before she was hospitalized.
A study by the VA showed that most people were taking too much medication because they forgot to split their tablets. 2 Two-thirds of the patients received more than the intended dose. Pharmacists caught these errors because the patients came in ahead of schedule to refill their prescriptions. In more than half of the events, the involved doses were available commercially.
In the article on tablet splitting in order to save money, Clark identified a few additional risks: 1.
Medication factors. Some medications or formulations are not suitable for splitting, including capsules, enteric-coated or extended-release tablets, very small or asymmetrical tablets, and teratogenic agents (e.g., bosentan).
Various studies suggest that obtaining an accurate dose from a split tablet is uncertain, even if the tablet is scored. 1 In one study, 94 volunteers were asked to split 10 25-mg tablets of hydrochloro-thiazide; 41% of the split tablets deviated from the correct weight by 10%, and 12% of the tablets deviated from the correct weight by more than 20%. Other research cited by Clark corroborates the significant variation in tablet halves with rates of inaccuracy ranging from 5% to 72%. 1.
S afe P ractice R ecommendations : Health care providers should make every effort to use commercially available oral tablets, when available, in both inpatient and outpatient settings. However, tablet splitting may still be necessary if the drug is not available in the patient-specific dose or if the patient’s inability to afford the medication as an outpatient outweighs the risks involved with tablet splitting. In view of these circumstances, Clark, the VA, and the Institute for Safe Medication Practices (ISMP) offer some suggestions.