Key takeaways:
Amoxicillin (Amoxil) and penicillin are antibiotics that treat a variety of bacterial infections, including strep throat.
Penicillin is an older antibiotic, and it doesn't fight as many types of bacteria as amoxicillin. But they're both first-choice options for treating strep throat.
Both medications are generally well-tolerated. They have similar side effects overall, too, such as diarrhea and nausea. But they can cause allergic reactions, and some of these can be serious.
Save on related medications
Amoxicillin (Amoxil) and penicillin are two common antibiotics. For good reason, too. They’re both relatively affordable and treat many different bacterial infections.
Strep throat is one of those bacterial infections. It can cause uncomfortable symptoms, such as a sore throat and fever.
Both medications are first-choice treatments for strep throat, but how do you know if one is a better choice for you? Here’s what you should know.
Amoxicillin vs. penicillin at a glance
The table below highlights the key similarities and differences to consider when comparing amoxicillin versus penicillin.
| Amoxicillin | Penicillin | |
|---|---|---|
| Drug class | Penicillin antibiotic | Penicillin antibiotic |
| How it works | Stops bacteria from building their cell walls | Stops bacteria from building their cell walls |
| Forms |
|
|
| Typical strep throat dosage |
|
|
| Common side effects |
|
|
| Generic available? | Yes | Yes |
| Available brand-name products for treating strep throat |
|
|
| Related combination products for treating strep throat |
|
|
Below are more details on six ways that amoxicillin and penicillin compare for strep throat.
1. Amoxicillin works against more types of bacteria than penicillin
Amoxicillin and penicillin belong to a group of antibiotics called penicillin antibiotics. They both work by blocking bacteria from building the protective cell wall they need to survive. This weakens the bacteria and eventually kills them.
Penicillin was the first naturally occurring antibiotic ever discovered. It treats ear, nose, and throat infections (including strep throat), lower respiratory tract infections, and skin infections.
But these infections can be caused by different types of bacteria, and penicillin doesn't work against all of them. That's because many bacteria have developed resistance to penicillin. This means that some bacteria have changed in certain ways such as building different types of protective walls. These changes then allow them to survive, even when an antibiotic is used to treat them.
Amoxicillin has a slightly different chemical structure than penicillin. This helps it reach and treat more types of bacteria that penicillin can’t. You can take amoxicillin to treat:
Upper respiratory tract infections affecting the ear, nose, and throat, such as strep throat
Lower respiratory infections, such as pneumonia
Skin infections, such as cellulitis
Helicobacter pylori (H. pylori) infections
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Amoxicillin is sometimes used off-label for other infections too, such as Lyme disease, actinomycosis (an infection that commonly affects the face or neck), and endocarditis (an infection of the heart valves).
Augmentin targets even more bacteria than amoxicillin
Amoxicillin also comes in a combination product called amoxicillin / clavulanate (Augmentin), which can make treatment more successful in certain situations. That’s because some resistant bacteria produce enzymes that break down amoxicillin. Clavulanate helps block these enzymes, so Augmentin can treat infections that amoxicillin alone can't. But it's also more likely to cause diarrhea, so amoxicillin is usually tried first.
Augmentin XR is another option. It’s an extended-release (longer-lasting) version of the same medication.
2. Penicillin also comes as an injection
Penicillin is available in an oral form (penicillin V potassium, or penicillin VK) and an injectable form (penicillin G potassium, or penicillin G).
The oral form is much more common and comes as:
Oral tablets: 250 mg, 500 mg
Oral solution: 125 mg per 5 mL, 250 mg per 5 mL
For strep throat, a single shot of penicillin G benzathine (Bicillin L-A) in the muscle is another option. This can be a helpful option if you have trouble finishing a 10-day course of pills.
Amoxicillin, though, is only available in oral options. But it still comes in a greater variety of forms than oral penicillin. These include:
Capsules: 250 mg, 500 mg
Tablets: 500 mg, 875 mg
Chewable tablets: 125 mg, 250 mg
Oral suspension: 125 mg per 5 mL, 200 mg per 5 mL, 250 mg per 5 mL, 400 mg per 5 mL
3. You may take amoxicillin less often than penicillin for strep throat
People usually take penicillin or amoxicillin for about 10 days to treat strep throat. Your exact dosage will depend on your age, body weight, and medical history.
With either medication, take the full prescribed course, even if you feel better after a few days. Stopping an antibiotic too soon can make the treatment not work as well. It may also lead to antibiotic resistance.
Penicillin dosages for strep throat
A typical oral penicillin dosage for strep throat varies by age group:
Adolescents and adults: 500 mg 2 times daily, or 250 mg 4 times daily
Children: 250 mg 2 to 3 times daily
Amoxicillin dosages for strep throat
Amoxicillin is typically taken 2 to 3 times daily to treat strep throat. It’s also important to note that the dosage for children who weigh less than 40 kg (88 lbs) is based on body weight.
Typical amoxicillin dosages for strep throat include:
Adults and adolescents: 1,000 mg once daily, or 500 mg 2 times daily
Children weighing less than 40 kg (and older than 3 months): 50 mg per kg of body weight once daily (up to 1,000 mg per day), or 25 mg per kg of body weight 2 times daily (up to 500 mg per dose)
With either medication, take the full prescribed course, even if you feel completely better after a few days. Stopping an antibiotic too soon can make treatment not work as well. It may also lead to antibiotic resistance.
4. Amoxicillin may taste better than penicillin
For children, or anyone who needs a liquid, taste can play a role in choosing a medication. Amoxicillin oral suspension is generally considered to taste better than penicillin oral solution. Your healthcare team may recommend amoxicillin for this reason.
Luckily, some liquid products come flavored, and your pharmacist may be able to add flavoring to help improve the taste.
5. Their side effects are similar, with a few differences
Both medications can cause side effects, and many of them affect your digestive system. These are the most common side effects of each.
| Penicillin side effects | Amoxicillin side effects |
|---|---|
|
|
Serious risks and side effects of amoxicillin and penicillin
Allergic reactions, including potentially severe ones, are possible. If you’re allergic to a penicillin antibiotic, your healthcare team may avoid giving you other penicillin antibiotics. Examples of these include dicloxacillin, ampicillin, and oxacillin.
If you think you’ve had a reaction in the past to penicillin, let your healthcare team know. They can help you determine if you're truly allergic to penicillin. Symptoms of a reaction may include hives, swelling, or difficulty breathing.
If your penicillin allergy is severe, your healthcare team may also avoid prescribing certain medications from another group of antibiotics, known as cephalosporins. These medications are chemically similar to penicillin antibiotics, and may cause a similar reaction.
Another rare but serious side effect is Stevens-Johnson syndrome (SJS). SJS is a rare skin condition that can cause rashes, blisters, and skin peeling. If you notice these symptoms, seek care immediately, as it’s considered a medical emergency.
Clostridium difficile (C. diff) infections are a common side effect of both medications. This is an infection that causes symptoms such as infectious diarrhea, cramps, and fever. It’s highly contagious and can cause severe complications. Contact your prescriber if you experience these symptoms.
6. They have slightly different drug interactions
Amoxicillin and penicillin interact with many of the same medications, which makes sense since they're so similar. Both can interact with:
Probenecid: Healthcare professionals sometimes prescribe this gout medication alongside penicillin antibiotics on purpose. It slows how quickly your body clears the antibiotic, which raises antibiotic levels in your blood.
Methotrexate: Penicillin antibiotics can make it harder for your body to get rid of methotrexate (Trexall, Otrexup, others). This can raise your risk of methotrexate side effects, such as mouth sores and nausea.
Tetracycline antibiotics: Common examples of these include doxycycline (Vibramycin) and minocycline (Minocin). These medications work against amoxicillin and penicillin, making it harder to fight off your infection. However, it’s unlikely you’ll be taking both types of antibiotics at the same time.
Amoxicillin has additional interactions to watch for:
Allopurinol: Taking allopurinol (Zyloprim) with amoxicillin can make you more likely to get a skin rash.
Blood thinners: Amoxicillin may make blood thinners, such as warfarin (Coumadin, Jantoven), work more strongly than usual. This effect raises your risk of bleeding. Your healthcare team may want to check your bloodwork more often while you're taking both medications.
This isn't a complete list of either antibiotics’ interactions. Before starting one of these antibiotics, give your prescriber and pharmacist a list of all the medications and supplements you take.
How to save on amoxicillin and penicillin
Amoxicillin and penicillin are available as brand-name medications. But you can also find both as lower-cost generics. GoodRx can help you navigate the ways to save on your prescription.
Without insurance, the average retail price of 20 tablets of penicillin VK 500 mg — about 10 days worth of medication — is about $15.71. With a free GoodRx coupon, you may be able to get it for as low as $8.20 at certain pharmacies.
The average retail price of 20 capsules of amoxicillin 500 mg — about 10 days worth of medication — is about $13.14. With a free GoodRx coupon, you may be able to get it for as low as about $11 at certain pharmacies.
You can also access discounted prescription medications with a GoodRx Companion subscription. Over 250 medications (including certain forms of amoxicillin and penicillin) are available for free, with hundreds more for under $10. The program also includes benefits to help you cut your self-pay costs, such as lower prices for online care visits, discounts on dental care, and other health services.
Frequently asked questions
No, amoxicillin and penicillin aren’t typically taken together for strep throat. Penicillin and amoxicillin work the same way to stop bacteria from growing and spreading. Taking them together doesn't add any benefit for strep throat, and you may experience more intense side effects than you would otherwise.
No, penicillin isn’t necessarily stronger than amoxicillin, or vice versa. Both penicillin and amoxicillin work well to treat strep throat. One is not considered stronger than the other.
Amoxicillin works against more types of bacteria, which makes it more useful for some other infections. But treating more types of bacteria doesn't make an antibiotic stronger. The better choice depends on the type of infection and the bacteria causing it.
Penicillin targets a narrower range of bacteria than amoxicillin, so it's less likely to disturb other bacteria in your body. That may lower the risk of antibiotic resistance. Amoxicillin may also be more likely to cause skin rashes. Plus, penicillin can be given as a single shot, which may be preferable if you or a loved one have difficulty taking pills.
No, amoxicillin and penicillin aren’t typically taken together for strep throat. Penicillin and amoxicillin work the same way to stop bacteria from growing and spreading. Taking them together doesn't add any benefit for strep throat, and you may experience more intense side effects than you would otherwise.
No, penicillin isn’t necessarily stronger than amoxicillin, or vice versa. Both penicillin and amoxicillin work well to treat strep throat. One is not considered stronger than the other.
Amoxicillin works against more types of bacteria, which makes it more useful for some other infections. But treating more types of bacteria doesn't make an antibiotic stronger. The better choice depends on the type of infection and the bacteria causing it.
Penicillin targets a narrower range of bacteria than amoxicillin, so it's less likely to disturb other bacteria in your body. That may lower the risk of antibiotic resistance. Amoxicillin may also be more likely to cause skin rashes. Plus, penicillin can be given as a single shot, which may be preferable if you or a loved one have difficulty taking pills.
The bottom line
Amoxicillin (Amoxil) and penicillin are both first-choice options for strep throat, but they have some key differences. Amoxicillin covers more bacteria than penicillin, so it may work better in some situations. You can also take it less frequently. For strep throat, amoxicillin can be taken 1 to 2 times daily, and the liquid tends to taste better. Oral penicillin is usually taken 2 to 4 times daily, but it's also available as a one-time injection. Both medications can cause diarrhea, nausea, and allergic reactions. If you're allergic to either one, your healthcare professional will likely choose a different antibiotic altogether.
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References
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