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

Ampicillin: effect, areas of application, side effects

by Josephine Andrews
Published: Last Updated on 448 views

Ampicillin is a broad-spectrum antibiotic from the aminopenicillin group. The active ingredient can be used in a variety of bacterial infections and is well tolerated. In patients with a penicillin allergy, however, it triggers severe allergic reactions. Here you can read everything you need to know about the effects of Ampicillin, dosage and application as well as possible side effects.

This is how ampicillin works

Like other penicillins, ampicillin interferes with bacterial cell wall formation:

In order to be able to divide and multiply, bacteria have to constantly dissolve and rebuild their cell wall in places. Ampicillin specifically binds to the bacterial enzymes that rebuild and strengthen the cell wall.

This prevents the bacteria from dividing and multiplying, which is known as the bacteriostatic effect. The immune system can thus master the invaders who are unable to divide and ultimately kill them.

intake, degradation and excretion

After taking ampicillin, only 30 to 60 percent of the active ingredient is absorbed into the blood via the intestinal mucosa. Maximum blood levels are reached about two hours after ingestion.

The antibiotic is mainly excreted unchanged in the urine. About an hour after ingestion, half of the active ingredient has left the body in this way.

When is ampicillin used?

Ampicillin is used to treat many bacterial infections, such as infections:

  • in the ear, nose and throat area (ENT area)
  • the kidneys and urinary tract
  • of the gastrointestinal tract
  • of the eyes
  • the airways

Always take antibiotics exactly as your doctor has told you. Do not stop taking them prematurely, even if the symptoms of the infection have disappeared. Otherwise bacteria remaining in the body can become insensitive (resistant) to the antibiotic used.

How Ampicillin is used

Ampicillin has historically been given in tablet and capsule form, as well as intravenously (directly into a vein). Due to the significantly poorer absorption compared to the very similar amoxicillin , ampicillin is now hardly ever prescribed for oral administration. If so, the application looks like this:

The tablets or capsules are taken three to four times a day due to the rapid excretion of the active ingredient. This is the only way to achieve a steady level of active ingredients in the body.

The dosage depends on age, body weight and other parameters and ranges from two to a maximum of eight grams of ampicillin. The duration of therapy is usually seven to ten days, but should be continued for at least two to three days after the symptoms have subsided.

In the case of intravenous therapy , too, the dosage depends on age, body weight and other parameters and is individually adjusted.

Ampicillin is often combined with a so-called beta-lactamase inhibitor such as sulbactam. This increases the effect of the antibiotic on bacterial strains that can break down penicillins into ineffective metabolites.

What are the side effects of ampicillin?

In more than every tenth patient, the antibiotic resolves nausea, stomach pain , vomiting, diarrhea and skin reactions with itching and redness. Since the latter indicates an allergic reaction, patients must contact a doctor if they experience this side effect.

Rarer side effects include changes in liver enzyme levels, dizziness, headaches and other non-specific symptoms.

What should be considered when taking Ampicillin?


Ampicillin should not be used if there is a known hypersensitivity to penicillins (“penicillin allergy”).


Some other active ingredients may interact with ampicillin when used at the same time.

For example, taking medications for gout (such as probenecid, allopurinol ) at the same time can lead to higher ampicillin blood levels and thus an increased risk of skin reactions.

Coumarin-type anticoagulants (such as phenprocoumon , warfarin) may have an increased effect when combined with ampicillin.

The drug methotrexate, used to treat rheumatoid arthritis, various types of cancer and autoimmune diseases, is inhibited in its elimination when combined with ampicillin. This increases methotrexate levels in the body, which can also increase the undesirable drug effects of this active substance.

Another important interaction is between ampicillin and the hormonal contraceptive ” pill “. If these medicines are used together – even if this is done at different times – the contraceptive effect of the pill is not guaranteed. It should therefore be additionally prevented by a non-hormonal method, for example with a condom.

If digoxin (medicine against heart failure) is taken at the same time, increased absorption of digoxin is possible.

age restriction

Ampicillin can also be used in newborns, children and adolescents in a correspondingly reduced dose to treat bacterial infections.

pregnancy and breast feeding period

Available data do not indicate adverse effects of ampicillin on pregnancy or the health of the child. Ampicillin is therefore one of the antibiotics of choice during pregnancy.

The active ingredient passes into breast milk. If side effects occur in the child, such as diarrhea, breastfeeding may have to be interrupted for the duration of treatment with Ampicillin (after consultation with the doctor treating you). However, most children have no symptoms. Ampicillin is therefore one of the antibiotics of choice during breastfeeding.

How to get medication with ampicillin

Drugs with ampicillin are subject to prescription in Germany and Austria. In Switzerland, there are no longer any preparations with this active ingredient on the market.

Since when is ampicillin known?

Ampicillin was introduced to the market in 1961. Before that, only so-called gram-positive bacteria could be treated with penicillins. In addition, the active ingredients had to be administered as an injection or infusion .

The active ingredient ampicillin, on the other hand, is a broad-spectrum antibiotic that is also effective against gram-negative bacteria and can be used orally (e.g. in the form of tablets).

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