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Harvard Commentaries
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School

Medical Myths Medical Myths

Is Splitting Pills Okay?

October 09, 2013

By Robert H. Shmerling M.D.

Beth Israel Deaconess Medical Center

Do you split your pills? Many people do in an effort to spread their health care dollar as far as possible. And it may seem like a good idea.

For example, suppose you take a 30-milligram pill once each day. Depending on your health insurance and your pharmacy's prices, the price of a month's supply might be the same as (or only slightly more than) a month's supply of 60-milligram pills. So, why not get the higher-dose tablets, take a half a pill each day and make your prescription last 2 months instead of one?

Or you may split your pills because you're taking a dose of the medicine that's smaller than the lowest available dose.

But does the medication work just as well that way? Or, is that a myth? Recent evidence suggests that it depends on the medication and how you split it.

The Case Against Splitting Pills

It's clearly a bad idea to split certain pills. (And it should say so right on the bottle.) For example, some pills have a special coating to protect the stomach or to slow down absorption of the medicine. If split, the coating may not be effective. Your stomach may suffer or the drug may be absorbed too quickly to last all day.

It also can be difficult to split the pills evenly. That's true even for "scored" pills - those with an indentation that makes it easy to break the pill in half. Even if a pill is easy to break, it often breaks unevenly. Small pills are particularly difficult to break evenly.

And, keep in mind that doses lower than the smallest pill available have rarely been tested as rigorously as the full dose.

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"But I Used a Knife."

A sharp knife or scissors might seem like reasonable ways to cut pills. But, consider the results of a recent study performed in Belgium. When study volunteers used a kitchen knife or scissors, the dosage was off by more than 25% about 20% of the time.  Meanwhile, a commercial pill splitter was much more accurate: Errors of more than 25% occurred in just 8% of cases.

For some drugs, it may not matter if the dose varies a bit. But many medicines have a "narrow therapeutic window." In other words, small differences in dose can make the medication not work at all or cause an overdose. Accurate pill splitting - or avoiding the practice altogether - is particularly important for these drugs.

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What's the Solution?

Before splitting your pills, ask your pharmacist whether it's OK for your particular medicine. Another option is to ask your pharmacist to split your pills for you using a precise splitter.

In addition, drug makers should study smaller doses and make them available to allow easy dose reduction. 

Or, the solution may actually be a solution - the dosages of liquid formulations are much easier to adjust than pills.

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The Bottom Line

Splitting pills may be acceptable, but it's more acceptable for some medicines than others. If you've been told to split your pills, make sure you're doing it correctly or ask for help. And if you're taking a very small dose, ask your doctor whether you need the medicine at all.

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Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.

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