When your doctor prescribes a medication for you, it is ONLY for you. Every prescription has this warning on it somewhere:
It's not for your spouse, your kids, your dog, your neighbor, your cousin, a friend in need, or anyone else.
It's for YOU.
Medications are dangerous. Medications treat specific conditions. You are NOT a doctor, and it is NOT up to you (or appropriate) to diagnose the condition of another person.
Too many people give some or all of their medication to another person, usually their spouse. Some are sneaky about it, others are quite open about it. I've even worked with pharmacists that suggest it to patients like it is their place to do that. It's not.
I've even had people call me up at the pharmacy and tell me their spouse's or child's condition and then say, "How should I dose this _____ medication I have here? I can use that to treat this condition, right?"
I don't answer questions like that. There's a million things that could go wrong and patient safety is THE most important aspect of our job.
So if you're a patient that is giving YOUR medication to a spouse, child, or whoever, STOP. You're not a medical professional. What if the person you're giving it to has an allergy to the medication? You could risk their life while you're "playing doctor." Just don't do it.
If you're a pharmacist that's suggesting to patients that they give their medication to another person, STOP. You know better. I'm sure your drug knowledge is top notch and your advice might be accurate, but it is not your place. Just don't do it.