Penicillin and amoxicillin are the first-choice antibiotics for strep throat. Both are highly effective against the bacteria that cause the infection, and Group A Strep has never developed resistance to either one. The standard course lasts 10 days, and most people start feeling better within a day or two of their first dose.
Penicillin and Amoxicillin: The Go-To Options
Penicillin V is the classic treatment. Adults typically take 500 mg twice daily for 10 days, while children take a lower dose two or three times daily. It works well, but the dosing schedule can be inconvenient for some people.
Amoxicillin is prescribed just as often, partly because it comes in chewable tablets and flavored liquid suspensions that are easier for children. It can also be taken once daily, which makes the full 10-day course simpler to complete. The once-daily dose is weight-based for children and caps at 1,000 mg for adults.
For people who are unlikely to finish 10 days of pills, there’s a single-shot option: an intramuscular injection of benzathine penicillin G. A nurse or doctor administers it in one visit, and the treatment is done. This is especially useful for children or in situations where completing an oral course is a concern.
Options if You’re Allergic to Penicillin
A penicillin allergy doesn’t leave you without options, but the alternatives aren’t quite as straightforward. The two main backup classes are cephalosporins and macrolides (like azithromycin).
Cephalosporins are closely related to penicillin and are generally the next choice if your allergy is mild (a rash, for example, rather than a severe reaction like throat swelling or anaphylaxis). Many people with a mild penicillin allergy tolerate cephalosporins without problems. If your reaction to penicillin was severe, though, cephalosporins are usually avoided.
Macrolides like azithromycin and clindamycin are reserved for people who truly can’t take any penicillin-type drug. The reason they aren’t first-line is resistance. Among invasive Group A Strep isolates tested in 2023, 27% were resistant to macrolides and 26% were resistant to clindamycin. That means roughly one in four strep infections may not respond to these drugs at all. When they are used, susceptibility testing is recommended to make sure the specific strain will respond.
Why the Full 10 Days Matters
You’ll likely feel dramatically better within 24 to 48 hours, which makes it tempting to stop taking the pills early. But the 10-day course isn’t just about clearing your symptoms. It’s designed to fully eliminate the bacteria from your throat and prevent complications, most notably acute rheumatic fever, a condition that can damage the heart valves. Rheumatic fever typically develops one to five weeks after an untreated or undertreated strep infection, so finishing the entire course is the primary way to prevent it.
Stopping antibiotics early also increases the chance of the infection bouncing back, sometimes requiring a second round of treatment.
How Quickly You’ll Feel Better
Most people notice their fever breaking and their throat pain easing within the first one to two days on antibiotics. You become non-contagious even faster: within about 12 hours of your first dose. That’s the threshold schools and daycares typically use before allowing kids to return.
Even though you feel better quickly, lingering mild soreness for a few days is normal and doesn’t mean the antibiotic isn’t working. Over-the-counter pain relievers and warm fluids can help bridge that gap while the medication finishes its job.
What Happens Without Treatment
Strep throat will sometimes resolve on its own, but leaving it untreated carries real risks. Beyond rheumatic fever, untreated strep can lead to kidney inflammation, abscesses around the tonsils, and spread of the infection to nearby tissue. Antibiotics dramatically reduce all of these risks. They also shorten the window during which you can pass the infection to others, cutting contagious time from days or weeks down to roughly half a day.