Ampicillin: Uses, Doses, Side Effects, and Buying Safely

Ampicillin is a penicillin-family antibiotic used for many bacterial infections including ear, throat, urinary tract and some intestinal infections. It kills bacteria by stopping their cell wall growth. Doctors prescribe it by mouth or by injection depending on how serious the infection is.

Typical oral doses for adults are 250–500 mg every 6 hours for mild to moderate infections. For more serious infections doctors may give 1–2 g by IV every 4–6 hours. Children’s doses are usually calculated by weight; common pediatric dosing is 50–100 mg per kg per day divided into multiple doses. Always follow the exact prescription from your healthcare provider—these numbers are common ranges, not rules for self-treatment.

What to watch for

Common side effects include nausea, diarrhea, and rash. If you get watery or bloody stool, high fever, severe skin reaction, swelling of face or throat, or trouble breathing stop the drug and seek emergency care—these can signal serious reactions. If you know you are allergic to penicillin, do not take ampicillin and tell your provider about past reactions.

Ampicillin can interact with other drugs. It may reduce the effectiveness of certain oral contraceptives in rare cases, so consider extra birth control methods while taking it. It can also interact with blood thinners and other antibiotics. Tell your doctor or pharmacist about all medicines and supplements you take before starting ampicillin.

How to take and store it

Take oral ampicillin on an empty stomach for best absorption—usually one hour before or two hours after a meal—unless your doctor advises otherwise. Finish the full course even if you feel better early; stopping early can let bacteria survive and become resistant. Store pills at room temperature away from moisture; keep liquid suspensions refrigerated if the label says so and shake before use.

Want to buy ampicillin online? Only buy from licensed pharmacies that require a prescription. Check for pharmacy accreditation, a valid physical address, and clear contact info. Beware of sites that sell antibiotics without asking for a prescription or offer unusually low prices—those drugs may be counterfeit, expired, or unsafe. If you’re buying from another country, check legal and import rules where you live.

If you have kidney problems, are pregnant, breastfeeding, or care for a child, talk to a clinician before using ampicillin. If symptoms don’t improve within 48–72 hours after starting treatment, contact your provider. When used properly, ampicillin is effective and safe for many infections, but proper dosing, allergy checks, and safe sourcing matter.

Antibiotic stewardship matters: avoid using leftover pills or taking smaller doses to "save some" for later. Misusing ampicillin helps create resistant bacteria that are harder to treat. If you have questions about side effects or mixing with herbal products like St. John's wort, ask a pharmacist—some supplements change how drugs work. Keep a list of medicines and allergies in your wallet, and bring it to appointments. Proper records help providers choose safer options quickly in emergencies. Keep questions ready for every visit.