Ampicillin: uses, dosing, side effects & brands
Ampicillin is a medicine sold in the U.S. under 3 brand and generic names. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Available as
- Injectable
- Sold as
- 3 products — Ampicillin Sodium, Penbritin-S and Polycillin-N
- Prescription?
- Prescription only
- Generic available?
- Yes
- What the pharmacy pays
- about $13 for a 30-count supply — not your price
Every ampicillin product we track (3)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
| # | Drug | Rating | Type | Form | Generic? | Pharmacy pays | |
|---|---|---|---|---|---|---|---|
| 1 | Not yet rated | Prescription | Injectable | Generic | $13 | View → | |
| 2 | Not yet rated | Prescription | Injectable | Generic | $13 | View → | |
| 3 | Not yet rated | Prescription | Injectable | Generic | $13 | View → |
Combination products containing ampicillin
A combination is a different drug — different dosing, different warnings. It is listed here so you can find it, not so you can substitute it.
How long ampicillin keeps
No ampicillin label we read sets a separate limit for after opening, but they do specify how it must be stored — and the stability behind any date assumes those conditions.
Ampicillin and breastfeeding
From LactMed, the US National Library of Medicine’s Drugs and Lactation Database — quoted, not rewritten.
Full LactMed record for ampicillin: levels in milk, effects in breastfed infants, and the drugs it would consider insteadSubstantial information indicates that ampicillin produces low levels in milk that are not expected to cause adverse effects in breastfed infants. Occasionally disruption of the infant's gastrointestinal flora, resulting in diarrhea or thrush have been reported with penicillins, but these effects have not been adequately evaluated. Ampicillin is acceptable in nursing mothers.
National Institute of Child Health and Human Development, record revised January 15, 2025. LactMed states its information is not a substitute for professional judgement.
What people report to the FDA about ampicillin
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 3,012 reports naming ampicillin, and the FDA flagged 85% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- drug hypersensitivity351 reports
- pyrexia157 reports
- pneumonia145 reports
- rash134 reports
- diarrhoea132 reports
- acute kidney injury99 reports
- dyspnoea90 reports
- nausea78 reports
Read these as a signal, not a rate. A report does not mean ampicillin caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label.
Source: openFDA drug/event (FAERS), retrieved August 25, 2026.
Related calculators
Frequently asked questions
Can you take ampicillin with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run ampicillin against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What brand names is ampicillin sold under?
We track 3 ampicillin-containing products in the U.S.: Ampicillin Sodium, Penbritin-S and Polycillin-N. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does ampicillin come in?
Across the brands we track, ampicillin is currently marketed as injectable, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic ampicillin?
Yes. Our catalog lists 1 generic ampicillin product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.
Cite this page
- APA
- pharmaranks. (2026, July 24). Ampicillin: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/ampicillin
- MLA
- “Ampicillin: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/ampicillin.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for ampicillin on DailyMed (NIH) ↗.