Home Medicines Tetracycline: effect, areas of application, side effects

Tetracycline: effect, areas of application, side effects

by Josephine Andrews
Published: Last Updated on 268 views

Tetracycline is the prototype of the tetracycline group of antibiotics. As broad-spectrum antibiotics, these act against a large number of different bacteria. A special feature of tetracyclines is that they are also effective against intracellular pathogens, i.e. bacteria within a cell. Here you can read everything interesting about tetracycline: effect, application and side effects.

This is how tetracycline works

Tetracycline antibiotics inhibit the production of proteins in many bacteria, which the germs need for their metabolism and structure (cell membrane). Bacterial enzymes that are already present remain unharmed.

Tetracycline therefore only inhibits the growth of the bacteria, but does not kill them. The antibiotic therefore has a bacteriostatic effect, but not a bactericidal one.

Since tetracycline has long been used against many bacterial infections, many bacteria have become resistant to it. In particular, incorrect use – such as taking it for too short a time, taking it unnecessarily or taking it too often – specifically contributes to resistant bacteria surviving and spreading.

The bacteria can gain their resistance in several ways, for example by pumping the antibiotic out of the cell in a targeted manner, by proteins that protect the ribosome (= place of formation of the enzymes in the bacterial cells), or by changing the ribosome structure, which means that tetracycline is no longer available can bind.

intake, degradation and excretion

After ingestion, tetracycline is absorbed into the blood through the intestinal wall. The highest blood levels are measured after two to four hours. The antibiotic easily reaches most tissues of the body via the blood.

The antibiotic is excreted via the liver with the bile into the intestines and is partly absorbed again via the intestinal mucosa (enterohepatic circulation).

About half of it is broken down in the liver, the other half leaves the body unchanged. After eight to nine hours, the tetracycline blood level has halved again.

When is tetracycline used?

Tetracycline is used against bacterial infections with tetracycline-sensitive bacteria, especially respiratory, urinary tract, vaginal, and gastrointestinal infections. It can also be used successfully for acne and rosacea skin diseases .

Since tetracycline antibiotics also act within the cells, they are also among the drugs of choice for infections with legionella, listeria, mycoplasma, rickettsia and chlamydia.

In a fixed combination with the antibiotic metronidazole and bismuth oxide, tetracycline is also used to eliminate (eradicate) the “stomach germ” Helicobacter pylori.

This is how tetracycline is used

Tetracycline is taken as a tablet or capsule. The duration of use and the dosage depend on the type of infection. Usually, 250 to 500 milligrams of tetracycline are taken on an empty stomach two to four times a day, i.e. one hour before or two hours after eating. The capsules are taken in an upright position with a glass of water as they can damage the lining of the esophagus if they dissolve in the throat.

Take tetracycline only with a glass of water and not with milk, coffee, tea, mineral water or fruit juice.

There should be an interval of about six hours between the individual doses. This is important so that the active substance level in the blood is approximately the same at all times.

Although the symptoms of the disease usually improve quickly under antibiotic therapy, it is essential that the antibiotics are taken for the entire prescribed period, otherwise resistant pathogens can easily form.

What are the side effects of tetracycline?

Since tetracycline also works against the natural intestinal bacteria, those treated very often experience digestive problems, nausea, vomiting and diarrhea. In addition, more than one in ten patients develop inflammation of the stomach, inflammation of the mucous membranes in the mouth and throat, inflammation of the vaginal mucosa and fungal infections.

Adverse drug effects such as changes in the blood count, severe skin reactions and allergic reactions (such as rash, itching, shock ) appear in less than one percent of patients. In these cases, the antibiotic must be discontinued immediately and a doctor informed.

What should be considered when taking tetracycline?


Tetracycline must not be used in:

  • Known hypersensitivity to tetracycline antibiotics
  • Children under eight years of age (except for life-threatening infections)


Tetracycline must be taken at a distance from food, since food and, in particular, polyvalent electrolytes (such as magnesium, calcium, aluminum, iron, zinc ) form poorly soluble complexes with the antibiotic that can no longer be absorbed through the intestines.

Milk, cheese and other milk products in particular, as well as zinc and iron tablets and antacids (medicines against heartburn) should only be taken two to three hours apart from the antibiotic.

In type 2 diabetics, taking tetracycline can lead to increased blood sugar reduction from sulfonylureas ( glibenclamide , glimepiride , tolbutamide). If it is necessary to take it at the same time, the blood sugar must be checked closely.

Tetracycline may also increase the effect of coumarin-type anticoagulants (such as phenprocoumon and warfarin), so patients with coagulation disorders should monitor their coagulation levels closely.

The side effects of therapy with methotrexate in cancer or chronic inflammatory joint diseases can be increased by the combination with tetracycline.

In rare cases, tetracycline can affect the contraceptive effect of the pill . In order to ensure reliable contraception, women should therefore also use non-hormonal contraceptive measures such as condoms throughout the menstrual cycle .

Tetracycline absorbs UV light . As a result, those treated are very sensitive to UV light for the duration of the treatment. Direct sunlight or a visit to the solarium can lead to severe skin irritation similar to sunburn .

Avoid excessive sunbathing and solarium visits while using tetracycline. It is also advisable to apply a good sunscreen to the skin .

age restriction

Children from eight years of age, adolescents and adults may be treated with tetracycline in an appropriately adjusted dosage. Particular caution is required in patients with hepatic or renal impairment.

pregnancy and breast feeding period

The active substance should not be used during pregnancy and lactation. There are better studied alternatives. At least up to the 16th week of pregnancy, an absolutely necessary therapy with tetracycline is at least possible, after that the active substance is strictly contraindicated.

Short-term use of tetracycline for five to ten days is considered harmless while breastfeeding. You can continue breastfeeding during this time. On the other hand, prolonged intake cannot be reconciled with breastfeeding.

How to get medication with tetracycline

Tetracycline requires a prescription in Germany, Austria and Switzerland in every dosage and package size. This also applies to combination preparations with other active ingredients.

Since when is tetracycline known?

Tetracycline was discovered and studied by scientists in the United States in 1945. Just three years later it was used on humans. To date, numerous derivatives of tetracycline have been developed that have improved properties.

There are numerous generic drugs with the active ingredient tetracycline on the German drug market. Prescription medicines that are manufactured directly in the pharmacy (such as creams) are also occasionally prescribed.

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