Amoxicillin and penicillin are the first-line antibiotics for strep throat, and most courses last 10 days. The specific medication you’re prescribed depends on your age, whether you have any drug allergies, and how easily you can stick to a multi-dose schedule. Here’s what to expect from the most common options.
Amoxicillin and Penicillin: The Go-To Choices
Group A strep bacteria have never developed resistance to penicillin or amoxicillin, which is why they’ve remained the standard treatment for decades. For most people, amoxicillin is the preferred pick because it tastes better in liquid form (a real factor for kids) and can be taken just once or twice a day.
Penicillin V is the oral tablet form. Adults and teenagers typically take it twice daily for 10 days. Children take a lower dose two or three times a day for the same duration. It works just as well as amoxicillin, but the more frequent dosing schedule makes it slightly less convenient.
There’s also a single-shot option: an injection of long-acting penicillin given in the muscle. This is sometimes used when there’s concern that someone won’t complete a full 10-day course of pills. One injection and you’re done, no pills to remember.
Options If You’re Allergic to Penicillin
If you have a penicillin allergy, your doctor has several alternatives. The choice depends on how severe your allergy is.
For mild allergies (a rash but no breathing problems or swelling), a class of antibiotics called cephalosporins is typically safe. Cephalexin, taken twice daily for 10 days, is the most common one prescribed. Cefadroxil is a similar option that only needs to be taken once a day.
For more serious penicillin allergies, the options shift to different antibiotic families entirely:
- Azithromycin is a 5-day course, which makes it the shortest treatment available. You take a larger dose on day one, then a smaller dose for the next four days.
- Clarithromycin is taken twice daily for 10 days.
- Clindamycin is taken three times daily for 10 days.
One important caveat: roughly 1 in 3 group A strep infections now show resistance to erythromycin and clindamycin. Azithromycin and clarithromycin belong to the same antibiotic family as erythromycin, so resistance can affect them too. Penicillin and amoxicillin don’t have this problem, which is another reason they remain the first choice when allergies aren’t an issue.
Why the Full 10 Days Matter
Most people start feeling noticeably better within one to two days of their first dose. That fast improvement tempts a lot of people to stop taking their medication early. This is a mistake.
The 10-day course isn’t just about clearing your symptoms. It’s designed to fully eliminate the bacteria from your throat, which reduces the risk of complications. Historically, untreated strep infections led to rheumatic fever in up to 3% of cases during outbreaks. Rheumatic fever can permanently damage heart valves. Completing a full course of antibiotics prevents this in most cases. Stopping early leaves bacteria behind that can rebound or cause these downstream problems.
The exception is azithromycin, which stays active in your tissues longer and only requires five days.
How Quickly You’ll Feel Better
Once you take your first dose, you’re typically no longer contagious within 12 hours. Schools and daycares generally follow this same 12-hour rule before letting kids return. Fever and the worst of the throat pain usually start improving within the first day or two.
While you wait for the antibiotic to kick in, over-the-counter pain relievers like ibuprofen and acetaminophen can help manage throat pain and bring down a fever. Cool drinks, warm broth, and throat lozenges also help, though they’re comfort measures rather than treatment.
Children vs. Adults
The same antibiotics are used for both children and adults. The difference is dosing. Children’s doses are calculated by body weight, while adults receive standard fixed doses. For amoxicillin, a child might get a weight-based dose once daily, capped at 1,000 mg. An adult taking penicillin V typically takes 500 mg twice a day.
Liquid formulations are available for younger children who can’t swallow pills. If a child has trouble completing a 10-day course (a common challenge with toddlers), the single injection of long-acting penicillin avoids the issue entirely. It’s given once at the doctor’s office, and no follow-up doses are needed at home.
When Antibiotics Aren’t Working
If your symptoms haven’t improved at all after two to three days on antibiotics, something else may be going on. The initial diagnosis could have been wrong (viral infections cause similar symptoms and won’t respond to antibiotics), or in rare cases the particular strain may be resistant to the antibiotic you were given. This is more likely with azithromycin or clindamycin than with amoxicillin or penicillin. Contact your prescriber if you’re not seeing any improvement, since switching medications or re-testing may be needed.