What is Penicillin Used For?

Penicillin is an antibiotic that is used to treat a wide range of bacterial infections in many different parts of the body. It was discovered in 1928 by Alexander Fleming and has saved millions of lives over the last century. Notably, penicillin is not a single antibiotic but a group of antibiotics called penicillins, which in turn belong to a larger group of drugs called beta-lactam antibiotics. Please continue reading to learn more about the uses of penicillin antibiotics.

What happens when you take penicillin?

Penicillin works by killing bacteria that cause infections in the human body. Specifically, penicillin inhibits the synthesis of the bacterial peptidoglycan cell wall. Similar to the human skin, bacterial cell walls are responsible for many essential roles, including giving the bacteria its shape and providing overall protection. Therefore, taking this medicine will interfere with the protective cell wall, and bacteria are compromised as osmotic pressure pushes water into the cell. As a result, bacteria are killed and prevent the infection from spreading further.

What is penicillin most commonly used for?

Penicillin antibiotic treatment is mainly used to treat bacterial infections caused by both Gram-positive bacteria, including:

Skin infections
Dental infections
Ear, nose, and throat infections
Pneumonia and other respiratory tract infections
Urinary tract infections
Sexually transmitted infections
Brain and spinal cord infections such as meningitis
Rheumatic fever (a complication of untreated strep throat or scarlet fever)

Using antibiotics, including treatment with penicillins, is not effective against the common cold, flu, COVID-19, and other viral infections. Taking antibiotics when they are not needed (for infections caused by viruses) can lead to the emergence of antibiotic-resistant bacteria.

Antibiotic resistance is a threat to the effectiveness of antibiotics that can save lives. To prevent penicillin resistance, you should only take penicillin V, penicillin G, and other penicillin antibiotics when they are prescribed by a healthcare professional to treat a confirmed or suspected bacterial infection.

What are the different types of penicillins?

There are two natural penicillins, penicillin V and penicillin G, which are directly derived from a fungus called Penicillium chrysogenum that occurs in nature.

Described below are semisynthetic penicillins (also referred to as second-generation penicillins) that are made in the lab to be resemblant to natural penicillins.

Aminopenicillins (ampicillin, amoxicillin),
Antistaphylococcal penicillins (nafcillin, cloxacillin, dicloxacillin, oxacillin),
Broad-spectrum penicillins (piperacillin, mezlocillin, carbenicillin, ticarcillin), and a beta-lactamase inhibitor (clavulanic acid).

Penicillins are available in various dosage forms. Besides oral administration with oral tablets and capsules, chewable tablets, oral solution, and oral suspension, penicillin antibiotics can also be given as an injection, either intravenously (into a vein) or intramuscularly (into a muscle).

What are the side effects of penicillin?

Common side effects of penicillin include stomach cramps and ache, nausea, vomiting, and diarrhea. When penicillin is administered intravenously or intramuscularly, it can cause temporary side effects such as redness, pain, and swelling at the injection site. You should tell your doctor if these side effects are severe or do not go away after a few days.

Less commonly, taking penicillin can cause more serious side effects, such as either a yeast infection (vaginal itching and/or discharge) or oral thrush (white patches in the mouth and throat). In rare instances, a temporary side effect causing a black hairy tongue can happen. Though this can look very worrisome, it typically goes away after completing the antibiotic. Call your doctor immediately if you develop these adverse effects.

Stevens-Johnson syndrome (SJS) is a very rare but serious side effect of penicillin. Let your doctor know and seek medical care immediately if you notice blistering skin rash, fever, and muscle aches.

Clostridium difficile (C. diff) infection is another rare side effect that is very contagious and can cause serious complications if not treated promptly. This is not specific for penicillins. All antibiotics can potentially cause C.diff infections. Inform your doctor if you develop severe stomach cramps, severe diarrhea, and fever.

What is a penicillin allergy?

Some people are allergic to penicillin and can develop severe symptoms of an allergic reaction, such as skin rash, hives, itching, trouble breathing, swelling of the lips or throat, or hoarseness. You should seek immediate medical attention if you develop signs and symptoms of an allergic reaction after taking penicillin.

It is worth noting that while 10% of the US population reports having an allergic reaction to penicillin in the past, only 1% of people have a true penicillin allergy. People with a penicillin allergy can be prescribed other non-penicillin broad-spectrum antibiotics to treat bacterial infections.

What precautions should I take while on penicillin?

Allergic reactions

Tell your doctor or pharmacist if you have ever had an allergic reaction to penicillin antibiotics, other antibiotics, or any other medications in the past.

Drug interactions

Interactions between penicillin and your other medicines can result in serious side effects or make one or both medications less effective. Give your doctor a complete list of your medications, including prescription drugs, over-the-counter medications, dietary supplements, and herbal products, before starting treatment with penicillin.

Storage

Store penicillin in a tightly closed container at room temperature, away from heat and moisture, and safely out of reach of children and pets. In case of an accidental overdose, call the poison control helpline or go to the nearest emergency room without delay.

Dosing

Read the prescription label carefully and take penicillin exactly as prescribed. Penicillin is usually taken in divided doses, typically 3 to 4 times a day. Do not make any dose adjustment, including dosing frequency and duration of the treatment, without the approval of your health care professional. Do not stop taking penicillin even if you no longer have symptoms. You need to finish the course of antibiotics to make sure your infection is completely treated.

If you miss a dose of penicillin, take it as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and go back to your regular dosing schedule. Do not take extra medicine to make up for a missed dose.

Oral contraceptives

Estrogen-containing birth control pills may not work properly when taking certain types of penicillin, such as penicillin V, amoxicillin, and ampicillin. Use other birth control methods to prevent an unwanted pregnancy during penicillin treatment.

Pregnancy and lactation

Penicillin belongs to the FDA pregnancy category B, meaning animal studies have not shown a risk to the unborn baby, but there are no adequate human studies in pregnant women to confirm the safety of the fetus. Penicillin may be secreted into breast milk at low levels and cause adverse effects in a nursing baby. Tell your doctor if you are pregnant or breastfeeding before starting treatment with penicillin. Call your doctor if you become pregnant while taking penicillin.

Is penicillin and amoxicillin the same thing?

Penicillin and amoxicillin both belong to a larger group of antibiotics called penicillins. The difference between them is that amoxicillin is a newer antibiotic and is effective against a broader range of bacteria.

Is penicillin better than amoxicillin?

Penicillin is not necessarily better than amoxicillin. Both antibiotics are used to treat many of the same bacterial infections. However, amoxicillin has a broader coverage, thus treating more bacterial species and may be preferred in some cases.

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