Medicines usually maintain efficacy past their expiration dates

Dear Dr. Roach: I recently tested positive for COVID using an expired home test, and I self-isolated for five days. I also realized every Tylenol, antihistamine, DayQuil, NyQuil and allergy pill that I had was past its expiration date. Some were only expired by a few months, but most were expired by two to four years. I guess I don't get sick often. My question is: Before I dispose of these, how effective are they, and are any of them dangerous to use? — K.L.Answer: Drug manufacturers are required to make expiration dates, and they guarantee that the drugs are what they say they are and are effective until a certain date (at least if they are stored properly in a cool and dark area). This does not necessarily mean that they become ineffective or dangerous after expiring, and many drugs have been proven to maintain efficacy for years or decades after the printed expiration date.A military study found that 90% of drugs are still effective 15 years after expiration. It is rare for a drug to become dangerous; however, the tetracycline class of antibiotics is one where toxicity has been found.In general, if a drug is a few months to a year past its expiration date, it is probably OK. (Liquid drugs, nitroglycerin and insulin are notable exceptions.) But at some point, you have to ask yourself whether it is worth the small risk of the medicine being less effective, especially for inexpensive over-the-counter drugs.Also, COVID test kits may have an extended expiration date. The Food and Drug Administration maintains a list at tinyurl.com/COVIDTestKitExpire.Dear Dr. Roach: Can you comment on N-acetyl cysteine (NAC), an over-the-counter (OTC) supplement for psychiatric illness? I am interested in its safety and effectiveness, and whether there any side effects or cautions when taking it.Also, what is the safe daily dosage, and how long does it take for benefits to occur? — L.B.Answer: NAC has been intravenously used for many years in medicine as a specific antidote to acetaminophen toxicity. It is also used via inhalation to thin out thick mucus so that it can be coughed out. As you say, several recent studies have looked at its effectiveness with a variety of mental health issues, including depression, obsessive-compulsive disorder, and cannabis use disorder. Although there is a risk of a severe allergic response when used intravenously, it is generally safe when used orally. Some studies have looked at the effectiveness of NAC by itself, while others looked to see whether NAC can improve outcomes in combination with standard treatments.Although the literature is mixed, I say that there is promise with this treatment. When I recommend it, it is most commonly with patients who do not want to use standard treatments or want the lowest possible dosage. The dose used in most studies is 1-3 grams daily.In one well-done study that looked at adults with major depression, the group that combined NAC with standard treatment showed superiority over those who received standard treatment alone. The difference was seen after 20 weeks of treatment. Not all studies showed a benefit.I want to emphasize that an OTC supplement, no matter how promising, is not a substitute for medical care, especially psychiatric care. If you have a mental health issue, ask your mental health provider about NAC.Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.