Ampicillin: What is it? When is it used? Side Effects, Tips and Warnings

It is derived from penicillin, which inhibits bacterial synthesis of the cell wall by inactivating transpeptidases on the surface of the cell membrane.

It is a β-lactam antibiotic with a side chain of the amino group attached to the structure of penicillin. Its mode of resistance is through the division of the β-lactam ring of Ampicillin by β-lactamase.

Ampicillin is effective against Gram-positive and some Gram-negative bacteria.

When is it used?

Ampicillin is a broad-spectrum antibiotic that is effective against many bacteria.

Ampicillin is prescribed for several bacterial infections, including urinary tract infections (bladder infection), middle ear infections, specific meningitis, and respiratory infections such as sinusitis (sinus infection) and pneumonia.


Ampicillin is used to treat infections of the middle ear, sinuses, stomach and intestines, bladder, and kidneys caused by susceptible bacteria.

It is also used to treat uncomplicated gonorrhea, meningitis, endocarditis, and other serious infections.


Due to the increased use of antibiotics, many bacterial strains have become resistant to penicillins, and bacteria that cause serious infections must be tested for resistance against penicillins and other antibiotics.

Side effects of Ampicillin

The oral ampicillin capsule does not cause drowsiness but can cause other side effects.

Most common side effects

The most common side effects of the Ampicillin oral capsule may include:

  • Nausea.
  • Vomiting
  • Diarrhea.
  • Eruption.

These effects may disappear in a few days or a couple of weeks if they are mild. Talk to your doctor or pharmacist if they are more severe or do not go away.

Serious side effects

Serious side effects and their symptoms may include the following:

  • Allergic reactions.
  • Flu-like symptoms, such as fever and body aches.
  • Painful red or purple rash that spreads.
  • Blisters that could cause the skin to break.
  • Diarrhea that lasts after you stop taking the medication.

Advice for Treatment

Even if you feel your infection has cleared, continue to take antibiotics until the course is over (unless a doctor tells you to stop). This is to prevent the infection from coming back.

Antibiotics are prescribed in short courses of treatment. Your doctor will tell you how long your treatment cycle will last; this usually does not last more than 14 days. If you still feel bad after finishing the course, return to see your doctor.

Some people develop redness and itching in the mouth or vagina after antibiotic treatment. If this happens to you, consult your doctor or pharmacist.

If you are taking the contraceptive ‘pill’ at the same time as this antibiotic, the effectiveness of the ‘pill’ can be reduced if you have a disease (vomiting) or diarrhea that lasts more than 24 hours.

If this happens, ask your doctor or pharmacist about what additional contraceptive precautions you should use in the next few days. It is unnecessary to use additional precautions for episodes of illness or diarrhea that last less than 24 hours.

Ampicillin can prevent the oral typhoid vaccine from working. If you must be vaccinated, ensure the person who treats you knows that you are taking this antibiotic.


Severe and occasionally fatal hypersensitivity reactions ( anaphylactoid ) have been reported in patients prescribed penicillin.

Although anaphylaxis is more frequent after parenteral administration, it has occurred in patients with oral penicillins.

Such a reaction is more likely to occur in patients with histories of hypersensitivity to penicillin and pathological data to multiple allergens.

At the beginning of therapy with any penicillin, careful investigation of hypersensitivity reactions prior to penicillins, cephalosporins, and other allergens should be carried out. The medication should be discontinued if an allergic reaction occurs and appropriate therapy instituted.

Oxygen, intravenous steroids, airway management, and intubation should also be given as directed.

Pseudomembranous colitis has been reported with almost all antibacterial agents, including Ampicillin, and can range in severity from mild to life-threatening. Therefore, it is essential to consider this diagnosis in patients who present with diarrhea after administering ant-agent agents.

Studies indicate that a toxin produced by Clostridium difficile is a primary cause of ” antibiotic-associated colitis .”

After establishing the diagnosis of pseudomembranous colitis, therapeutic measures should be initiated.

In moderate to severe cases, management with liquids and electrolytes, protein supplementation, and treatment with a clinically effective antibacterial drug against colitis should be considered.