What is penicillin?
Penicillin is a drug obtained from cultures of the brush mold fungus Penicillium chrysogenum (old name: P. notatum). In addition to penicillin, which occurs naturally in the mold, there are also semi-synthetic or fully synthetic (artificially produced) forms of this active ingredient.
Penicillin belongs to the class of antibiotics. These are active substances that act primarily against bacteria and are therefore used to treat bacterial infections.
The terms antibiotics and penicillin are often used synonymously. In fact, however, penicillins are only a subgroup of antibiotics. Other representatives of antibiotics include macrolides, aminoglycosides, and carbapenems.
When is penicillin used?
Penicillin is used against infections with sensitive germs. Important areas of application of penicillin include:
- tonsillitis (inflammation of the tonsils)
- Otitis media (inflammation of the middle ear)
- Sinusitis (inflammation of the sinuses)
- Bronchitis
- Scarlet fever
- meningitis (inflammation of the meninges)
- Inflammation of the inner lining of the heart (endocarditis)
- Urinary tract infections
- Biliary tract infections
- Bone inflammation (osteomyelitis)
- Rheumatic fever
- Syphilis
- Gonorrhea (gonorrhea)
- Listeriosis
- Typhoid and paratyphoid fever
- Bacterial dysentery (shigellosis)
- “Blood poisoning” (sepsis)
Different penicillins (see below) are sometimes considered for treatment of the various diseases. Sometimes the antibiotics are also prescribed as a preventive measure (for example, before an operation).
Which penicillins are there?
There are many different penicillins, which differ in their chemical structure. The natural penicillin discovered by Alexander Fleming is known as penicillin G. This is the most common type of penicillin.
In order to expand the spectrum of activity and circumvent resistance, further variants have been developed over the decades. They are produced partially or fully synthetically.
Important penicillins are:
- Penicillin F (penicillin I; δ2-pentenylpenicillin).
- Penicillin X (penicillin III; p-hydroxybenzylpenicillin)
- Penicillin K (penicillin IV; n-heptylpenicillin)
- Penicillin V (phenoxymethylpenicillin)
- Penicillin O (allylmercaptomethylpenicillin)
- Dihydroflavicin (n-amylpenicillin)
According to the spectrum of activity, a distinction is made between narrow-spectrum and broad-spectrum penicillins.
Narrow-spectrum penicillins
Narrowband penicillins are mainly effective against Gram-positive bacteria. This group of active ingredients includes:
- Penicillin G and longer-acting depot penicillins such as benzathine-benzylpenicillin (a salt of penicillin G that is barely soluble in water): They are acid labile and therefore must be administered intravenously (as a syringe or infusion). Administered by mouth (orally), stomach acid would break them down.
- Oral penicillins: These are acid-resistant and therefore can be given orally. They include penicillin V, propicillin, and azidocillin (the latter two are no longer available today).
Broad-spectrum penicillins
Broad-spectrum penicillins are effective not only against Gram-positive but also against some Gram-negative bacterial species. These agents include:
- Aminopenicillins: Ampicillin, amoxicillin.
- Acylaminopenicillins: Mezlocillin, Piperacillin
- Carboxypenicillins: They are no longer used today.
Those penicillins that are not resistant to the bacterial enzyme beta-lactamase are usually used as a combination preparation together with a beta-lactamase inhibitor, for example:
- Amoxicillin with clavulanic acid
- Ampicillin with sulbactam
- Piperacillin with tazobactam
How does penicillin work?
Penicillin belongs to the group of beta-lactam antibiotics. All representatives of this group have a so-called beta-lactam ring in their chemical structure.
The penicillin effect (i.e. the effect of all beta-lactam antibiotics) on dividing pathogens is therefore bactericidal.
Penicillin is ineffective on bacteria that are already fully grown, i.e. in which cell division no longer occurs. These bacteria are neutralized by the immune system.
Penicillin is mainly effective against Gram-positive bacteria (such as streptococci) and against some Gram-negative bacteria (such as meningococci). Gram is a dye used in the microscopic examination of bacteria. Depending on whether the examined bacterium accepts the dye (Gram-positive) or not (Gram-negative), the physician initiates appropriate antibiotic therapy.
Penicillin resistance
In relation to penicillin, this defense strategy involves the enzyme beta-lactamase, which some bacterial species produce. With this enzyme, the germs can override the beta-lactam ring of penicillin – and thus the bactericidal penicillin effect.
Such resistance is promoted by various factors. For example, penicillin is often taken in doses that are too short or too low. Then some bacteria in the patient’s body can survive the treatment and pass on their “experience” with the active substance.
Over time, resistance can thus develop in subsequent generations of bacteria. The unnecessary use of broad-spectrum penicillins – penicillins that are effective against many different bacteria – can also promote resistance.
How penicillin is used
Penicillins are usually taken orally (e.g., as penicillin tablets) or administered directly into a vein (intravenously) (as an injection or infusion). Some preparations (depot penicillins) are injected into a muscle.
Oral preparations contain acid-resistant penicillins such as azidozillin or penicillin V, which cannot be broken down by stomach acid. Non-acid-resistant penicillins such as penicillin G, on the other hand, must be administered bypassing the stomach (parenterally) in order to exert their effect (i.e., as an infusion).
The dosage depends on the active ingredient, the type of disease and the individual characteristics of the patient (height, weight, etc.). It is determined by the physician, and it is essential to adhere to it.
Duration of use
In any case, patients should not decide independently how long to use a penicillin medication, but should always adhere to the duration of use recommended by the doctor. Only then is it ensured that the medication can work properly.
What are the side effects of penicillin?
Penicillins are generally very well tolerated. However, they do not differentiate between “bad” bacteria (the invading pathogens) and the “good” bacteria in the intestines (intestinal flora), which are important for digestion, among other things.
Accordingly, nausea, vomiting and diarrhea are possible penicillin side effects. Other adverse effects that may occur include dizziness, confusion, and visual and hearing disturbances.
Penicillin allergy
Penicillins can cause allergic reactions. This is thought to occur in 0.5 to 2 percent of treatments.
A so-called pseudo-allergy must be distinguished from penicillin allergy. In this case, symptoms occur during treatment that resemble those of an allergic reaction (e.g., skin redness or swelling), but are actually side effects of the drug.
Penicillin allergy not always lifelong
Studies show that people who are allergic to penicillin once do not necessarily maintain that allergy permanently. The very next time penicillin is taken, the allergic reaction may not occur.
For this reason, a skin test (prick test) and a blood test should always be performed before penicillin is administered – even in patients who are classified as allergic. In this way, it can be ruled out that supposed allergy sufferers, who are actually no longer allergy sufferers, are given another drug instead of the well-tolerated and highly effective penicillin, which is perhaps less suitable for treatment.
What should be considered when using penicillin?
Penicillins should not be used if there is hypersensitivity to the respective active substance. In addition, the risk of cross-allergies should be considered in the case of penicillin hypersensitivity.
In addition, other contraindications apply to some penicillins. Some examples:
- Amoxicillin as well as amoxicillin/clavulanic acid are contraindicated in infectious mononucleosis (Pfeiffer glandular fever) and lymphocytic leukemia.
- Flucloxacillin is contraindicated in infectious mononucleosis (Pfeiffer glandular fever), lymphocytic leukemia, jaundice, and hepatic dysfunction with prior flucloxacillin administration.
Drug Interactions
Drug interactions may occur with concomitant use of penicillin and other drugs. For example, penicillin increases the effect of methotrexate, a drug used to treat cancer and various autoimmune diseases such as rheumatoid arthritis.
Before prescribing penicillin, doctors therefore always clarify whether a patient is using other medications and, if so, which ones.
As a general rule, experts recommend completely avoiding alcohol during antibiotic treatment. This is because both the antibiotic and the alcohol are broken down by the liver, placing a double burden on the detoxification organ. This can lead to or intensify side effects. In addition, the body is weakened by the infection, and the immune system is working at full speed. Alcohol puts even more strain on the organism, which can delay healing.
Many antibiotics are not compatible with milk, as its components hinder the absorption of the active substances in the intestine. However, this does not apply to penicillins. Milk and milk products can usually be combined with them without any problems.
The doctor or pharmacist treating you can explain in more detail when and how you should take your penicillin medicine.
Age restriction
Penicillin can be used from birth to treat a bacterial infection.
Pregnancy and breastfeeding
Penicillins are among the antibiotics of choice during pregnancy and breastfeeding. Observations to date have not shown any evidence of a harmful effect on fertility.
Nevertheless, before any prescription, the physician will always weigh the expected benefit against the theoretical risk of treatment.
Who discovered penicillin?
It was to be another ten years before the scientists Howard Florey and Ernst Boris Chain recognized the potential of the fungal active ingredient penicillin for the treatment of infectious diseases in humans. Together with Alexander Fleming, they were awarded the Nobel Prize for Medicine for their work in 1945.
