Ampicillin - Use | Dose | Side Effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Ampicillin belongs to antibacterial medicines (antibiotics), more precisely to penicillin group of antibiotics. It causes destruction of bacteria cell walls, which leads to bacteria cell death. This effect is called bactericidal effect. Because of these effects, Ampicillin is used for:

  • Ear infections
  • Sore throat caused by bacterial infection
  • Tonsillitis (inflammation of the tonsils)
  • Sinusitis
  • Bronchitis
  • Pneumonia
  • Gastrointestinal infections
  • Gonorrhea


Ampicillin should be avoided if:

  • You are allergic to any of beta-lactam antibiotics, such as: penicillin, cefuroxime, cephalexine, cefpodoxime, ceftriaxone, amoxicillin, co-amoxiclav and others.
  • You have viral infections, such as: colds, flu, infectious mononucleosis (caused by Epstein-Barr virus) and others.
  • You have leukemia. Ampicillin in these patients may cause rash.

Do not use this medicine longer than your doctor prescribed. Prolonged use of antibiotics may lead to increased growth of microorganisms.

This medicine may cause anaphylaxis - serious allergic reaction that can be fatal. Call your doctor immediately if you are experiencing symptoms of an allergy, such as: skin rash, urticaria, edema and shortness of breath.

Use of Ampicillin during pregnancy and breastfeeding

According to FDA, this medicine belongs to category B, which means that animal studies have shown no adverse effects to the fetus, but there are no studies in humans. This medicine can be used during pregnancy only if the benefit to the mother outweighs risk to the child.

Small quantities of this medicine pass into breast milk, which is why you should avoid use of this medicine while breastfeeding.

How to use

Recommended dosage:

Condition Dosage
Sinusitis, ear infections, sore throat caused by bacterial infection 250 mg every 6 hours (4 times a day).
Bronchitis From 250 mg to 1000 mg every 6 hours (4 times a day). Dose depends on the severity of infections.
Urinary tract infections 500 mg every 8 hours (three times a day)
Gonorrhea One dose of 2000 mg combined with Probenecid
Gastrointestinal infections From 500 mg to 750 mg 3 or 4 times a day
Intestinal infections From 1000 mg to 2000 mg every 6 hours (four times a day). Treatment lasts 2 -12 weeks, depending on severity of infections.

Note: Above table applies to adults and children weighing more than 40 kg (approximately 90 pounds).

Swallow the tablet whole with a full glass (8 ounces) of water.

Avoid use of alcoholic beverages while taking this medicine.

In children under the age of 10, dose should be reduced by half of recommended adult dosage.

Foods can decrease its absorption, therefore you should take this medicine 1 hour before meal or two hours after meal.

Use of Ampicillin with other medicines (Interactions)

Ampicillin should be avoided with following medicines:

  • Oral antidiabetic medicines. Concomitant use of Ampicillin with these medicines, increases risk of hypoglycemia (low blood sugar).
  • Medicines used to treat gout, such as: Probenecid. This medicine¬†reduces renal excretion of¬†Ampicillin which may lead to an increased concentration of Ampicillin in the blood and increased risk of side effects.
  • Allopurinol (medicine used to treat gout). Concomitant use of Ampicillin with this medicine, increases risk of skin allergic reactions.
  • Methotrexate (medicine used to treat cancers). Ampicillin reduces excretion of Methotrexate which may cause side effects.

It should be avoided in combination with alcoholic beverages, because alcohol may increase concentration of Ampicillin in the blood.

You should tell your doctor about all medicines you are taking, before you start using Ampicillin.

Side effects

Ampicillin may cause following side effects:

  • Hives
  • Skin rash
  • Itchy skin
  • Stevens-Johnson syndrome
  • Erythema multiforme
  • Toxic epidermal necrolysis
  • Anaphylactic reaction
  • Interstitial nephritis
  • Glomerulonephritis
  • Nausea
  • Vomiting
  • Diarrhea
  • Pseudomembranous colitis
  • Hepatic impairment (hepatitis and jaundice)
  • Low white blood cells count (leukopenia) and consequently weakened immune system
  • Thrombocytopenia (low platelet count) and consequently increased susceptibility to bleeding
  • Anemia
  • Headaches
  • Dizziness

Call your doctor immediately if you are experiencing any side effects.

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.

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