9 Things You Should Know About Penicillin Antibiotics
Key takeaways:
Penicillin antibiotics are safe and effective treatment options for many bacterial infections. Common examples are penicillin, amoxicillin, and Augmentin (amoxicillin/clavulanate).
Each penicillin antibiotic has unique side effects and drug interactions. The most common general side effects are nausea, diarrhea, and an upset stomach.
If you think you've had an allergic reaction to penicillin in the past, let your healthcare provider know. They can do skin testing to determine if you have a serious penicillin allergy.
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Penicillin antibiotics are common, low-cost medications that treat many bacterial infections. You've likely received a prescription for one if you've ever had a skin infection or a pesky case of strep throat.
Penicillin antibiotics are considered safe to take. However, details about this family of antibiotics aren’t always common knowledge. There are also a few interactions and side effects to be aware of. Here, we'll talk about nine things to know before taking penicillin antibiotics.
1. Many penicillin antibiotics are available
Many penicillin antibiotics are available for you to use. All of them are approved as prescription medications — none are available over the counter. They kill bacteria by interfering with their protective structure. And each one is dosed and given slightly differently depending on the infection being treated. Factors like your age, medical history, and personal preferences all play a role.
Top examples of penicillin antibiotics include:
You and your healthcare provider have many dosage forms to choose from, too. Penicillin and ampicillin both come in oral and injectable forms. But some are only available as oral options, like amoxicillin, Augmentin, and dicloxacillin. Many, though, are available as intramuscular (IM) or intravenous (IV) injections.
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2. Some penicillin antibiotics are more common than others
Treating bacterial infections can be tricky. Just because you feel sick doesn't mean you have an infection caused by bacteria. In fact, many infections can be caused by viruses (like, the common cold, flu, COVID-19) or fungi rather than bacteria. And in some cases, you may need more than one antibiotic to treat your infection.
Penicillin antibiotics are one type of medication your healthcare provider may recommend. Oral penicillins are especially common. Some of the common penicillin antibiotics are amoxicillin, penicillin V, and dicloxacillin. Augmentin is also popular at U.S. pharmacies.
3. Penicillin antibiotics treat many bacterial infections
Penicillin antibiotics are first-choice treatments for many common bacterial infections. Children and adults can use them to treat ear, nose, and throat infections, lower respiratory infections, and skin infections.
Some other bacterial infections that penicillin antibiotics can treat are:
Urinary tract infections (UTIs)
Meningitis (brain or spinal cord infection)
Endocarditis (a heart infection)
Helicobacter pylori (H. pylori) infection
4. There are some side effects to keep in mind
Like all medications, penicillin antibiotics have side effects to keep in mind. Specific side effects vary by medication, but the most common side effects of penicillin antibiotics include:
Nausea
Upset stomach
Diarrhea
Vomiting
Mild rashes
They’re less common, but other side effects have also been reported. For instance, it's possible to experience a temporary condition called black hairy tongue. Signs of a black hairy tongue may include a discolored tongue, tickling, and bad breath. This condition is harmless and will usually go away after you finish taking the antibiotic that's causing it.
Another rare but serious side effect is severe skin rashes, including reports of Stevens-Johnson syndrome (SJS). Signs of SJS include fever, muscle aches, and severe skin blisters. As a precaution, you should stop taking your antibiotic and seek medical attention right away if you develop a severe blistering rash.
All antibiotics, including penicillin antibiotics, can also cause Clostridium difficile (C. diff) infections — albeit in rare cases. Possible symptoms of C.diff include watery diarrhea, fever, and intense stomach cramps. This infection is highly contagious and can have serious complications if it’s not treated right away.
5. Penicillin allergies aren’t always what they seem
Many people report having a penicillin allergy. However, more often than not, these allergies turn out to be false alarms.
For instance, medication side effects and symptoms of certain health conditions, like viral infections, can sometimes mimic allergic reactions. You may have also been told you had a mild allergic reaction to penicillin as a child. If so, there’s a good chance you've outgrown your allergy as an adult.
In fact, while about 10% of people report having a penicillin allergy, only about 1% of people have a serious penicillin allergy when properly tested. Studies show that most people only have mild reactions (e.g., rash) that don't put them at risk for serious symptoms like anaphylaxis.
Even though there are questions surrounding penicillin allergies, it’s still a good idea to be cautious when taking penicillin antibiotics. If you think you've had a reaction to penicillin in the past, let your healthcare provider know. They can test to see if you’re allergic to penicillin antibiotics.
6. Drug interactions aren’t common, but they’re possible
Penicillin antibiotics interact with a few other medications. There are amoxicillin interactions, Augmentin interactions, and others to keep in mind. Some interactions can contribute to side effects. Others can lead to a less effective treatment.
Drug interactions vary by medication, but several interactions are common among the group. This isn’t a complete list, but these medications tend to interact with penicillins:
Warfarin (Coumadin, Jantoven)
Allopurinol (Zyloprim)
Tetracycline antibiotics (e.g., doxycycline, minocycline)
Live cholera vaccine (Vaxchora)
Live typhoid vaccine (Vivotif)
If you're worried about drug interactions, you should contact your healthcare provider or pharmacist right away. And be sure to have your updated medication list ready for review. This way, they can check this list and see if any medications interact.
7. Penicillin antibiotics vs. cephalosporin antibiotics
Cephalosporins are a class of antibiotics that includes medications like cephalexin (Keflex), cefdinir, and ceftriaxone. Cephalosporins are chemically (structurally) related to penicillin antibiotics. They work in similar ways and treat similar types of infections, but you can’t substitute one for another.
Because of their similarities, people with a penicillin allergy are at a slightly higher risk of having an allergic reaction to cephalosporins. This is especially worrisome if your allergy is severe. Your healthcare provider will choose the best antibiotic for you depending on factors like your infection type, age, and history of allergic reactions.
8. Penicillin and penicillamine have very different uses
Despite how they sound, penicillin and penicillamine have very different uses.
Penicillamine (Depen, Cuprimine) is a medication used to treat Wilson's disease (excess copper levels), cystinuria (a rare genetic condition), and rheumatoid arthritis (RA). Penicillamine is not an antibiotic like penicillin. Its main job is to help your body get rid of certain metals and proteins in your body.
In Wilson's disease, penicillamine attaches to copper so your body can remove it through your urine. Lower copper levels helps improve liver, mental, and physical problems caused by the condition. In cystinuria, penicillamine attaches to cystine, a protein that causes stones in your kidneys and bladder. The way it works to help treat people with RA isn't known.
9. There are ways to save on penicillin antibiotics
There are many ways to save on penicillin antibiotics. GoodRx can help you navigate your options, which may include GoodRx discounts, copay savings cards, and patient assistance programs. You can find penicillin antibiotics for as low as $5 with a free GoodRx discount.
The bottom line
Penicillin antibiotics treat many types of bacterial infections. Let your healthcare provider know if you experience any side effects while you’re taking your antibiotic. You should also let them know if you’ve potentially had an allergic reaction to a penicillin antibiotic in the past. They can do skin testing to determine if you’re allergic to penicillin antibiotics.
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References
American Academy of Allergy Asthma & Immunology. (2020). Penicillin allergy FAQ.
Calhoun, C., et al. (2022). Antibiotics. StatPearls.
Centers for Disease Control and Prevention. (n.d.). Is it really a penicillin allergy?
Centers for Disease Control and Prevention. (2017). Adult outpatient treatment recommendations.
Chaudhry, S., et al. (2019). Cephalosporins: A focus on side chains and 𝜷-lactam cross-reactivity. Pharmacy.
ClinCalc. (2021). Amoxicillin; clavulanate drug usage statistics, United States, 2013 - 2020.
Leekha, S., et al. (2011). General principles of antimicrobial therapy. Mayo Clinic Proceedings.
MedlinePlus. (2022). Cystinuria.
MedlinePlus. (2022). Endocarditis.
Mejias, S. G., et al. (2022). Penicillamine. StatPearls.
Ren, J., et al. (2020). Antibiotic-induced black hairy tongue: Two case reports and a review of the literature. Journal of International Medical Research.
