Penicillin and amoxicillin are the top recommended antibiotics for strep throat. The CDC lists both as the first-choice treatment for group A strep pharyngitis, and a standard course lasts 10 days. If you’re allergic to penicillin, several effective alternatives exist depending on the type of allergy you have.
Penicillin and Amoxicillin: The First Choice
Penicillin and amoxicillin have been the go-to treatments for strep throat for decades, and group A strep bacteria have never developed resistance to them. That’s rare in the world of antibiotics, and it’s one reason they remain the standard recommendation. Amoxicillin is often preferred for children because it tastes better in liquid form and can be taken once or twice daily instead of multiple times a day.
A full course runs 10 days for both drugs. Adults typically take penicillin V at 500 mg twice daily, while amoxicillin is dosed at up to 1,000 mg once daily or 500 mg twice daily. Children’s doses are calculated by weight. The 10-day course matters even though you’ll feel better well before it ends. Stopping early doesn’t fully clear the bacteria from your throat, which raises the risk of the infection bouncing back or causing complications.
Alternatives If You’re Allergic to Penicillin
Penicillin allergies are common, but the alternatives depend on what kind of reaction you’ve had. If your reaction was mild (a rash, for instance, rather than throat swelling or difficulty breathing), first-generation cephalosporins like cephalexin are a solid option. These are closely related to penicillin but are generally safe for people whose allergies aren’t severe. A typical adult dose is 500 mg twice daily for 10 days.
If you’ve had a serious allergic reaction to penicillin, the swelling-and-breathing-trouble kind, cephalosporins are off the table too because of the chemical similarity. In that case, your provider will likely choose a macrolide antibiotic. Azithromycin and clarithromycin are the most commonly prescribed in this category because they cause fewer stomach problems than erythromycin, the older macrolide that’s technically the guideline recommendation. Clindamycin is another option that works well against strep.
Why Macrolides Aren’t First Choice
You might wonder why azithromycin (often called a “Z-pack”) isn’t recommended for everyone, since it only takes five days instead of ten. The answer is resistance. Group A strep has been developing increasing resistance to macrolide antibiotics over the past several years. Australian surveillance data found that erythromycin resistance in strep climbed from under 4% before 2016 to a peak of roughly 9.5% in 2021 and 2022. Clindamycin resistance followed a similar pattern, reaching 11.1% in 2022. Both dropped somewhat in 2023, but the trend is concerning enough that these drugs are reserved for people who genuinely can’t take penicillin-type antibiotics.
By contrast, group A strep has shown zero resistance to penicillin and amoxicillin. That’s why they remain the default.
How Quickly Antibiotics Work
Most people start feeling noticeably better within one to two days of their first dose. Fever typically breaks within 24 hours, and throat pain gradually eases after that. You become much less contagious quickly too: most guidelines consider you no longer contagious after just 12 hours on antibiotics. Schools and daycares typically follow this same 12-hour rule before allowing kids to return.
Even though symptoms clear up fast, the full 10-day course (or 5 days for azithromycin) is essential. The bacteria can still be alive in your throat even when you feel fine.
Why Treating Strep Matters
Strep throat will often resolve on its own. The real reason antibiotics are strongly recommended isn’t just symptom relief. It’s to prevent rheumatic fever, a serious inflammatory condition that can damage heart valves. Rheumatic fever is rare in countries with good access to healthcare precisely because strep gets treated with antibiotics. It typically develops one to five weeks after an untreated strep infection, and once it occurs, it tends to come back with each future strep episode, sometimes requiring years of preventive antibiotics.
Antibiotics also reduce the risk of peritonsillar abscess (a painful pocket of pus near the tonsils) and help prevent spread to close contacts like family members and classmates. The combination of faster recovery, lower complication risk, and reduced contagiousness makes treatment worthwhile even when symptoms feel manageable.
What to Expect at Your Appointment
Before prescribing antibiotics, your provider needs to confirm that strep bacteria are actually causing your sore throat. Most sore throats are viral, and antibiotics do nothing for those. A rapid strep test takes about five minutes using a throat swab. If it’s positive, you’ll get a prescription that day. If it’s negative but strep is still suspected, a throat culture may be sent to a lab, with results in one to two days.
Once you have your prescription, start it as soon as possible. Take every dose on schedule through the full course. If your symptoms haven’t improved at all after two to three days on antibiotics, contact your provider. That could signal a resistant strain, a different diagnosis, or a complication that needs attention.