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Penicillin – Effect, Application & Risks


Penicillin is often the first choice when it comes to fighting diseases caused by bacteria . They kill the pathogens and prevent them from multiplying if there is no resistance.

What is penicillin?

In 1928, Alexander Fleming discovered penicillin . It is the first antibiotic of modern times. Penicillin is obtained from Penicillium fungi.

Penicillin is a type of antibiotic that is injected or given by mouth. It is used against bacterial infections and prevents the bacteria from forming a protective outer shell.

The drug needs to be taken for a long time to get the full effect. Since more and more bacteria are becoming resistant to penicillin, new synthetic antibiotics have to be developed again and again.

Application & Use

Penicillin is given for bacterial infections. Benzylpenicillin is always used as an injection because this penicillin is not acid-fast. Although this drug can be easily broken down by the bacteria, doctors like to administer it because of its good tolerability. The most common areas of application are infections with pneumococci , streptococci , diphtheria bacteria, meningococci and spirochetes.

Oral penicillins such as phenoxymethylpenicillin and propicillin can be given orally. They are less strong than benzylpenicillin but work the same way.

More potent against cleavage by bacteria are penicillinase-resistant agents such as oxacillin, flucloxacillin, and dicloxacillin. However, these only work against staphylococci , which in most cases are already resistant to antibiotics.

A modern variant of penicillin, for example, is amoxicillin . It is taken orally and helps with respiratory infections, infections in the urinary and bile ducts, blood poisoning , whooping cough and middle ear infections .


Taking penicillin can cause drug interactions. Many preparations prevent or reduce the absorption of hormones in the intestinal flora. This can make contraceptive pills worse because their effectiveness is reduced. If penicillin is taken, condoms should also be used as protection.

The simultaneous intake of antibiotics that inhibit bacterial growth and phenoxymethylpenicillin such as tetracyclines and erythromycin should be avoided. These active ingredients are only effective in adult bacteria.

Penicillin and indomethacin or salicylates should not be used together. These remedies are used for rheumatism . When taken together with penicillin, the concentration of phenoxymethylpenicillin is prolonged and increased.

Persistent diarrhea , increased urination or the simultaneous intake of aminoglycoside antibiotics impairs the absorption of penicillin and thus reduces the concentration and mode of action.

Taking penicillin can worsen the detection of sugar or bile pigments.

Risks & side effects

There are various risks and side effects that can occur from taking penicillin . These are not the rule and vary in severity. It also depends on whether penicillin was administered as a tablet, injection or ointment.

Tooth discoloration , tongue inflammation , stomatitis, dry mouth, changes in taste and gastrointestinal problems such as vomiting , nausea , diarrhea , loss of appetite and flatulence can occur.

It is possible to develop neutropenia, which means a reduction in the number of white blood cells. Thrombocytopenia, a decrease in blood platelets, also occurs. Other side effects can be: agranulocytosis, skin rash , hives , Lyell’s syndrome, drug fever, anemia , protein allergy reaction, kidney inflammation, facial swelling, tachycardia, blood vessel inflammation, shortness of breath , joint pain , allergic shock and bronchial muscle spasms.

If penicillin is taken over a long period of time, it can lead to an infestation of resistant fungi and bacteria around the large intestine. The consequences are diarrhea and intestinal inflammation. The penicillin should then be stopped immediately and replaced with another antibiotic. Vancomycin may be suitable.

Long-term and repeated use of penicillin can lead to so-called superinfections with bacteria or fungi that are already resistant. This can also lead to infections in the mouth or vaginal infections.

If allergic reactions, such as hives, occur immediately after taking penicillin, it is probably an allergy to penicillin. The treatment should then be stopped immediately and replaced with a suitable antibiotic.

Penicillin should only be taken during pregnancy after consultation with the doctor treating you . There are no known harmful effects.

Penicillin should be avoided during breastfeeding. The active ingredient is absorbed by the baby through breast milk and can lead to diarrhea and intestinal inflammation. Furthermore, this can lead to sensitization of the baby.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.