Will an expired antibiotic still work?

Answer 1

The expiration date on antibiotics is especially important to adhere to, when compared to expiration dates on most other prescription and over-the-counter drugs. When most drugs reach their expiration date, the worst thing that will happen is a slight decrease in potency, or they'll start to taste/smell/look different. This doesn't mean you should blindly ignore the dates on your prescription bottles, but it's generally not going to kill you to take an expired headache or allergy pill, and the assigned dates serve primarily a "better safe than sorry" function on behalf of the drug companies and pharmacies trying to cover all their bases in terms of patients harming themselves.

However, antibiotics are particularly time-sensitive drugs, and the primary concern is that the active drug compound will break down over time, and turn into a different chemical that is more difficult for the human body to metabolize. Specifically, these by-products can harm your kidneys and liver, and when those organs are impaired, you lose your ability to filter toxins and various chemical metabolites from your system. This can really mess up most of your bodily functions, especially your immune system, which, when weakened, is a big security hole in your body's defenses, and you have the potential to get a lot sicker than you normally would from everyday bacteria and viruses.

Another issue is that many antibiotics are dispensed in dosage delivery systems that require more maintenance on the part of the user than your average bottle of pills, which you can pretty much store anywhere and forget about. Many antibiotics are dispensed in liquid forms, which often require refrigeration or other specific temperature constraints, and like anything you keep in the fridge, there's only a limited window of time before decomposition will occur.

Antibiotics are also frequently prescribed with strict, specific dosing schedules. Most oral antibiotics require doses every 6, 8, or 12 hours, until the entire bottle of pills is finished. This is what is called a "course" of therapy, and it means that there is usually a set amount of the drug you're supposed to take over a set period of time, both in order for the drugs to reach their full effectiveness, and so that you don't take them for so long that they stop being effective at all. Drugs like certain Asthma inhalers and painkillers can be taken whenever, wherever, whether you need them all the time, or only a few times per year. Antibiotics are designed to work in the opposite way, which also means that they're not designed to last as long - it's just the nature of that particular group of drugs.

One more issue is that your prescribing physicians want to monitor your antibiotic usage every time you need them. If people went around taking antibiotics every time they suspected they were sick, and didn't follow the dosing instructions, it would become harder and harder to find specific antibiotics that really worked well, that people hadn't developed tolerance to. Imagine - the very first time someone hid their spare house key underneath their doormat, it may have been a very unexpected, very good, place to hide the key, and nobody would have thought to look there. But once the idea of the doormat being a 'good hiding place' spread, it became the most obvious place someone could look if they were trying to break into your house, so it stopped being an effective method of thwarting intruders. It's a crude analogy, but antibiotics kind of work the same way.

But the major point to take away here is that antibiotics should always be taken exactly as instructed, even if you think you're sure you have an infection and you don't need to consult your doctor, and even if your prescription from two years ago looks just the same as it always did. You don't want to compromise a good way of curing basic infections just because you're lazy/cheap/think you know better, right? I didn't think so. Ask your pharmacist if you have any questions about your prescription, any prescription - that's what they're there for, and they have your best interests in mind (pharmacists can't legally (at least in the US) dispense drug samples like doctors in their offices can, and generally speaking, most pharmacists see big drug companies as obstructive, obnoxious hindrances to the administration of basic health care, and they know "their game" enough not to arbitrarily slap short expiration dates on their prescriptions just so they can make more money - that's really not how it works!).