Amoxicillin is the most commonly prescribed antibiotic for strep throat in both children and adults. It’s the go-to choice because it’s effective, affordable, tastes better in liquid form for kids, and can be taken once or twice a day for 10 days. If you have a penicillin allergy, several alternatives work well, including certain cephalosporins, clindamycin, and azithromycin.
First-Line Treatment: Amoxicillin
Amoxicillin tops the list for a reason. Group A Streptococcus, the bacterium behind strep throat, has never developed resistance to penicillin-type antibiotics. That’s unusual in an era of growing antibiotic resistance, and it makes amoxicillin a reliable first choice. The standard course is 10 days, taken either once or twice daily. Most people start feeling noticeably better within one to two days of starting treatment. If you don’t see any improvement after 48 hours, that’s worth a call to your doctor.
Penicillin V (the pill form of penicillin) works equally well and is sometimes prescribed instead of amoxicillin. The two are essentially interchangeable for strep throat. Amoxicillin tends to be preferred because it comes in chewable tablets and flavored suspensions that are easier for children to tolerate.
Options If You’re Allergic to Penicillin
A penicillin allergy doesn’t leave you without options. The alternatives fall into three categories, and which one your doctor picks depends on the type of allergic reaction you’ve had.
- Cephalosporins (cephalexin, cefadroxil): These are closely related to penicillin but are generally safe for people whose penicillin allergy was mild, like a rash. They’re taken for 10 days and are considered nearly as effective as amoxicillin. However, if your allergy involved a serious reaction like throat swelling or anaphylaxis, cephalosporins are typically avoided.
- Azithromycin: Often known by the brand name Zithromax or “Z-Pack,” this is a 5-day course, which is shorter and more convenient. The downside is growing resistance. Studies in some regions have found resistance rates climbing to around 9%, meaning it won’t always work. It’s a reasonable backup, not a first choice.
- Clindamycin: This one is taken three times daily for 10 days. It’s effective but reserved for situations where other options aren’t suitable, partly because it carries a higher risk of digestive side effects.
- Clarithromycin: Another alternative in the same family as azithromycin, taken twice daily for 10 days. It faces the same resistance concerns.
Why the Full 10 Days Matters
The biggest mistake people make with strep antibiotics is stopping early. You’ll likely feel dramatically better after a day or two, and it’s tempting to quit once the sore throat fades. But the 10-day course (or 5 days for azithromycin) exists to fully eliminate the bacteria, not just knock them back enough that symptoms fade.
Stopping early increases the chance of the infection returning and, more importantly, raises the risk of complications. Untreated or undertreated strep can lead to rheumatic fever, a condition that causes inflammation of the heart, joints, and nervous system. During historical outbreaks, up to 3% of untreated strep infections progressed to rheumatic fever. That rate is lower today, but appropriate antibiotic treatment prevents it in most cases entirely. Completing the full course also protects the people around you. You become non-contagious within about 12 hours of your first dose, which is the threshold most schools and daycares use before allowing kids to return.
Getting Tested Before You Treat
Antibiotics should only be prescribed after a confirmed positive strep test, either a rapid antigen test (results in minutes) or a throat culture (results in a day or two). This matters because most sore throats are caused by viruses, and antibiotics do nothing for viral infections. Taking them unnecessarily contributes to antibiotic resistance and exposes you to side effects for no benefit.
Doctors use clinical scoring systems to decide who should be tested in the first place. These systems look at factors like your age, whether you have a fever, swollen lymph nodes in the neck, white patches on your tonsils, and whether you have a cough. A cough actually makes strep less likely, since it points more toward a viral cause. If your score suggests strep is unlikely, your doctor may skip the test altogether. If it suggests strep is plausible, you’ll get swabbed. Children under three are handled differently because strep often doesn’t produce the classic symptoms in that age group.
What to Expect During Treatment
Once you start antibiotics, fever typically breaks within the first day. Throat pain improves significantly within one to two days, though some mild soreness can linger. During those first 12 hours before you’re considered non-contagious, it helps to stay home and avoid close contact with others.
While waiting for the antibiotics to kick in, over-the-counter pain relievers like ibuprofen or acetaminophen can help manage throat pain and fever. Warm liquids, cold foods like popsicles, and throat lozenges (for older children and adults) can also provide comfort. None of these replace antibiotics, but they make the wait more bearable.
If your symptoms don’t improve at all after 48 hours on antibiotics, or if they initially improve and then worsen again, contact your doctor. This could mean the infection isn’t responding to the chosen antibiotic, that there’s a secondary issue like a peritonsillar abscess, or that the original diagnosis needs another look.