The go-to antibiotics for strep throat are penicillin and amoxicillin, both taken for 10 days. These have been the standard treatment for decades because group A strep bacteria have never developed resistance to them. If you’re allergic to penicillin, several alternatives work well, and a few options can be taken for as little as five days.
First-Line Antibiotics
Penicillin V and amoxicillin are the two antibiotics recommended before anything else. They’re inexpensive, effective, and narrow-spectrum, meaning they target the strep bacteria without wiping out as much of your normal gut flora as broader antibiotics would.
Amoxicillin is often the practical favorite, especially for kids, because it comes in a liquid form that tastes better and can be taken just once or twice a day. The typical course is once daily for 10 days. Adults and older teens on penicillin V usually take it twice daily at a higher dose (500 mg per dose) for the same 10 days.
There’s also an injectable option: a single shot of benzathine penicillin G. It’s given once in the clinic and you’re done. This is sometimes chosen when there’s concern someone won’t finish a full 10-day pill course, which is common with kids and teens. One shot handles the entire treatment.
Options If You’re Allergic to Penicillin
Your alternatives depend on the type of allergy you have. If your reaction to penicillin was mild (a rash, for example, rather than throat swelling or difficulty breathing), a first-generation cephalosporin like cephalexin or cefadroxil is typically prescribed. These are chemically related to penicillin but different enough that most people with a mild penicillin allergy tolerate them without problems. Both are taken for 10 days.
If your penicillin allergy is severe, meaning you’ve had anaphylaxis, significant swelling, or trouble breathing, cephalosporins are off the table too. In that case, the options include:
- Azithromycin: A five-day course, taken once daily. This is the well-known “Z-Pack.”
- Clarithromycin: Taken twice daily for 10 days.
- Clindamycin: Taken three times daily for 10 days.
These work, but they come with a caveat. Resistance to azithromycin, clarithromycin, and clindamycin among strep bacteria has been climbing in some parts of the world. A study of strep isolates in Shenzhen, China, found resistance rates above 70% for both macrolides (the drug class that includes azithromycin) and clindamycin. Resistance patterns vary by region, so these drugs remain useful in many areas, but they’re not as reliably effective as penicillin, which is one reason they aren’t first-line choices.
Shorter Treatment Courses
Most strep throat prescriptions run 10 days, which feels like a long time, especially once you’re feeling better by day two or three. The FDA has approved three antibiotics for a shorter five-day course: cefdinir, cefpodoxime, and azithromycin. Your provider may choose one of these if finishing a longer course is likely to be a challenge, though the standard 10-day course with penicillin or amoxicillin remains the preferred approach.
How Quickly You’ll Feel Better
Most people notice improvement within one to two days of starting antibiotics. Fever typically breaks first, followed by the sore throat easing up. If you’ve been on antibiotics for 48 hours and feel no better at all, that’s worth a call to your provider. It could mean the infection isn’t strep after all, or rarely, that the particular antibiotic isn’t working.
Feeling better quickly creates a temptation to stop taking the pills early. Finishing the full course matters. Stopping short can leave enough bacteria alive to cause a relapse or, more importantly, to trigger complications like acute rheumatic fever, a serious inflammatory condition that can damage the heart. About one-third of rheumatic fever cases follow strep infections where the person either didn’t get treated or didn’t complete treatment.
When You’re No Longer Contagious
Antibiotics knock down the contagious period fast. A large meta-analysis found that more than 90% of people test negative for strep bacteria in their throat within 24 hours of starting treatment. Current public health guidance in the U.S. says you can return to work or school after 12 to 24 hours on antibiotics, as long as you’re fever-free. Without antibiotics, strep can remain contagious for two to three weeks.
Why Treatment Matters Beyond Symptom Relief
Strep throat will often resolve on its own in terms of the sore throat and fever. The reason antibiotics are strongly recommended isn’t just comfort. Treatment prevents acute rheumatic fever, which can develop one to five weeks after an untreated strep infection and cause lasting damage to heart valves. It also reduces the risk of peritonsillar abscess (a painful pocket of infection near the tonsils) and helps stop the spread to others.
For people who have already had rheumatic fever, even a single new strep infection can trigger another attack. These patients are placed on long-term preventive antibiotics, sometimes for years, to keep strep at bay. This secondary prevention underscores just how seriously the medical community takes the link between untreated strep and heart complications.