In general, over-the-counter drugs are not a tax-deductible medical expense. However, the tax code specifically includes an exception for insulin, which is available over the counter in some formulations in some states. And, if you can get a doctor to write you a prescription for an "OTC" medication, it becomes deductible.
Prescribing Non-Prescription Drugs
According to the Internal Revenue Service, any medicine prescribed for you by a medical professional is tax-deductible "even if such drug is available without a prescription" — in other words, available over-the-counter. So if a doctor tells you to take 100 mg of aspirin every day, and you go buy a bottle of 100 mg tablets at a drugstore, the cost isn't deductible. But it is deductible if the doctor writes you a prescription for the same bottle.
The same deduction rules apply for prescribed over-the-counter medicine and regular prescription drugs. The prescription must be written or transmitted to the pharmacy electronically by a medical professional with the legal authority to prescribe medication. A doctor's simple suggestion or recommendation that you take a certain OTC drug is not enough.