What is the alternative drug if you are allergic to penicillin?
There’s no simple answer, since you didn’t mention the condition being treated. For strep throat, for instance, erythromycin is generally considered the first alternative in people with penicillin allergies, but there are lots of others that’ll do. People who’ve had a type I (anaphylactic) reaction to penicillin have about a ten percent chance of cross-reactivity to other beta lactams like cephalexin, hence the caution. It’s much less common when the penicillin allergy is a different type. If your brother is allergic to penicillin and prescribed amoxicillin, it’s a screw up. Either they made a mistake, or he’s not really allergic to penicillin. That’s not at all uncommon, by the way, to find that people have something that labels them as allergic when they aren’t.
