Before administering ampicillin,

• tell your doctor and pharmacist if you are allergic to ampicillin, penicillin, cephalosporins [e.g., cefaclor (Ceclor), cefadroxil (Duricef), or cephalexin (Keflex)], or any other drugs.
• tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially other antibiotics, allopurinol (Lopurin), anticoagulants ('blood thinners') such as warfarin (Coumadin), atenolol (Tenormin), oral contraceptives, probenecid (Benemid), rifampin (Rifadin), sulfasalazine, and vitamins.
• tell your doctor if you have or have ever had kidney or liver disease, allergies, asthma, blood disease, colitis, stomach problems, or hay fever.
• tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking ampicillin, call your doctor.
• if you have diabetes and regularly check your urine for sugar, use Clinistix or TesTape. Do not use Clinitest tablets because ampicillin may cause false positive results.

Ampicillin may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• upset stomach
• diarrhea
• vomiting
• mild skin rash

If you experience any of the following symptoms, call your health care provider immediately:

• severe skin rash
• itching
• hives
• difficulty breathing or swallowing
• wheezing
• unusual bleeding or bruising
• headache
• dizziness
• seizures
• sore mouth or throat