One of the least appreciated cost-savers in medical treatment is the simple act of splitting pills. Suppose you're a U.S. citizen with depression who needs to take Lexapro brand of escitalopram oxalate, a commonly prescribed antidepressant, at a typical starting dose of 10 milligrams (mg) per day. Let's figure out how much your treatment will cost, both by month and by day.

For purposes of illustration I'll use prices shown online at drugstore.com. If you buy thirty Lexapro 10-mg tablets (which is how the prescription is usually written) it will cost you $70.15 per month or $2.34 per day to get treated. But what if you buy Lexapro 20-mg tablets and take a half-pill each day? Medically, this treatment is the same. But look what happens to unit prices. Thirty Lexapro 20-mg tablets cost $69.99. We need just 10 mg per day, so we split the 20-mg tablets in half to make our 10-mg doses. (The tablets are even scored to make this easy.) In this case it costs you just $35.00 per month or $1.17 per day to get treated. Your daily price just dropped by half!

Isn't that amazing? And it's not just an isolated example. If you do a similar analysis for many other drugs, you'll find that taking half of a double-strength pill costs substantially less than taking all of a regular-strength pill. Or another way of saying this is that the cost of a month's treatment is driven more by the number of pills involved than by the total number of milligrams taken.

Is this an accident of pricing? Should we be whispering about this? Is this pulling something over on the drug companies? Hardly. If you think that multi-billion-dollar companies trading on the New York Stock Exchange make pricing mistakes, then I've got some choice swamp-land in Florida I'd love to sell you.

So why would drug companies create these pricing mismatches (read: opportunities)? To understand this, let's walk through two prescribing scenarios. First, suppose a doctor is prescribing Lexapro to a patient who is lucky enough to have drug insurance. The patient pays a predetermined co-payment for each month's worth of medication, so he or she has the exact same out-of-pocket expense whichever way the prescription is written. So will the doctor write for thirty 10-mg pills or fifteen 20-mg pills?

Your guess is probably right