The two go-to antibiotics for strep throat are penicillin V and amoxicillin. Both are equally effective at clearing the infection, and both require a full 10-day course. Amoxicillin is prescribed more often for children because it comes in a chewable tablet and liquid form that taste better, but either one works well for any age group.
Penicillin and Amoxicillin: The First Choice
Group A Streptococcus, the bacterium behind strep throat, remains universally susceptible to penicillin. That’s unusual in an era of rising antibiotic resistance, and it’s the main reason penicillin-based drugs have stayed the top recommendation for decades.
Penicillin V is typically prescribed at 500 mg twice daily for adolescents and adults, taken for 10 days. Children usually take 250 mg two or three times daily for the same duration. Amoxicillin is often the more practical choice, especially for kids, because it can be taken just once a day. The standard approach is a single daily dose based on body weight, up to a maximum of 1,000 mg per day. An alternative schedule splits that into two smaller doses.
Both medications are inexpensive, widely available, and cause relatively few problems. The most common side effects are nausea, diarrhea, and occasionally vomiting. Some children on amoxicillin develop a temporary yellowish or brownish discoloration of the teeth, which goes away. A true allergic reaction, involving a rash, hives, swelling of the face or throat, or difficulty breathing, is uncommon but requires immediate medical attention.
Options If You’re Allergic to Penicillin
If you have a penicillin allergy, the type of reaction you’ve had matters. People whose allergy caused a mild rash (not hives or swelling) can often safely take a first-generation cephalosporin instead, since the chemical overlap between these drugs and penicillin is small. Cephalexin, for example, is taken at 500 mg twice daily for 10 days in adults.
For people with a more serious penicillin allergy, cephalosporins are typically avoided too. In that case, doctors may prescribe erythromycin or a related antibiotic. However, resistance to these drugs has been climbing. Surveillance data from the current season in England found that 26% of invasive Group A Strep samples were resistant to erythromycin, up from a historical range of 4% to 20%. That trend makes these alternatives less reliable than they once were, and your doctor may want to confirm through a culture that the specific strain causing your infection will respond.
Azithromycin (often sold as a Z-Pack) is FDA-approved for strep throat but is not recommended as a primary treatment by clinical guidelines, partly because of these same rising resistance concerns. It may still be prescribed in certain situations, but it’s not the default fallback.
What Recovery Looks Like
Most people start feeling noticeably better within one to two days of their first dose. Fever usually breaks first, followed by a gradual easing of throat pain. If you feel no improvement after 48 hours on antibiotics, contact your doctor, as this could signal a resistant strain or a different diagnosis altogether.
You’re generally considered no longer contagious after about 12 to 24 hours on antibiotics. Most schools and workplaces follow a 24-hour rule: stay home until you’ve been on medication for at least a full day and your fever has resolved. That said, feeling better and being fully recovered are two different things. Finishing the entire 10-day course is essential even when your symptoms disappear after a few days.
Why Finishing All 10 Days Matters
Stopping antibiotics early because you feel fine is one of the most common mistakes with strep treatment. The bacteria can linger in your throat even after symptoms resolve, and cutting the course short increases the chance of the infection bouncing back or spreading to others.
More importantly, incomplete treatment raises the risk of rheumatic fever, a serious inflammatory condition that can damage the heart valves. During historical epidemics, as many as 3% of untreated strep infections led to rheumatic fever. That rate is lower now with routine antibiotic use, but the risk is real and entirely preventable by completing your prescription. A full course of appropriate antibiotics prevents rheumatic fever in most cases.
Antibiotics That Don’t Work for Strep
Not every antibiotic is effective here. Over-the-counter remedies, herbal treatments, and leftover antibiotics from a previous illness are not substitutes for a properly prescribed course. Strep throat requires a confirmed diagnosis, usually through a rapid antigen test or throat culture, followed by a targeted antibiotic. Taking the wrong drug won’t clear the bacteria and leaves you exposed to complications while also contributing to antibiotic resistance.