Ampicillin is used for:
Treating infections caused by certain types of bacteria.
Ampicillin is a penicillin antibiotic. It works by killing sensitive bacteria by interfering with formation of the bacteria's cell wall while it is growing. This weakens the cell wall and it ruptures, resulting in the death of the bacteria.
Do NOT use ampicillin if:
you are allergic to any ingredient in ampicillin or to any other penicillin antibiotic (eg, amoxicillin)
you are taking a tetracycline antibiotic (eg, doxycycline)
you have mononucleosis ("mono")
you have recently received or will be receiving live oral typhoid vaccine
Contact your doctor or health care provider right away if any of these apply to you.
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Before using ampicillin:
Some medical conditions may interact with ampicillin. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:
if you are pregnant, planning to become pregnant, or are breast-feeding
if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
if you have allergies to medicines, foods, or other substances
if you have a stomach infection or diarrhea
if you have had a severe allergic reaction (eg, severe rash, hives, difficulty breathing, dizziness) to a cephalosporin antibiotic (eg, cephalexin) or other beta-lactam antibiotic (eg, imipenem)
Some MEDICINES MAY INTERACT with ampicillin. Tell your health care provider if you are taking any other medicines, especially any of the following:
Tetracyclines (eg, doxycycline) because they may decrease ampicillin's effectiveness
Probenecid because it may increase the risk of ampicillin's side effects
Allopurinol because the risk of skin rash may be increased
Anticoagulants (heparin, warfarin) or methotrexate because the risk of their side effects may be increased by ampicillin
Aminoglycosides (eg, gentamicin), birth control pills, or live oral typhoid vaccine because their effectiveness may be decreased by ampicillin
This may not be a complete list of all interactions that may occur. Ask your health care provider if ampicillin may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.
How to use ampicillin:
Use ampicillin as directed by your doctor. Check the label on the medicine for exact dosing instructions.
Take ampicillin by mouth at least one-half hour before or 2 hours after eating.
Take ampicillin with a full glass of water (8 oz/240 mL).
Take ampicillin on a regular schedule to get the most benefit from it. Taking ampicillin at the same time each day will help you remember to take it.
To clear up your infection completely, use ampicillin for the full course of treatment. Keep using it even if you feel better in a few days.
If you miss a dose of ampicillin, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take 2 doses at once.
Ask your health care provider any questions you may have about how to use ampicillin.