Two medicines, side by side
Ampicillin vs penicillin g
Ampicillin and penicillin g are both labeled for bacterial infections. Drugs@FDA records approvals of ampicillin since 1966 and of penicillin g since 1990.
Check it at the source: the ampicillin FDA label on DailyMed (effective February 21, 2025); the penicillin g FDA label on DailyMed (effective September 16, 2020).
Highlights of the ampicillin record
Ampicillin (Penbritin-S) · label of February 21, 2025
Used for
From the label: indicationsAmpicillin for injection is indicated in the treatment of infections caused by susceptible strains of the designated organisms in the following conditions: Respiratory Tract Infections caused by Streptococcus pneumoniae. Staphylococcus aureus (penicillinase and nonpenicillinase-producing), H. influenzae, and Group A beta-hemolytic streptococci. […]
On the market
- Earliest approval on file
- December 29, 1966
- Generic labelers
- 17 labelers
- Pharmacy cost
- $0.441 per capsule
Supply and safety
- Shortage
- A presentation being discontinued
- Recalls
- 3
Highlights of the penicillin g record
Penicillin g (Pfizerpen) · label of September 16, 2020
Used for
From the label: indicationsTherapy Buffered penicillin G potassium for injection is indicated in the treatment of serious infections caused by susceptible strains of the designated microorganisms in the conditions listed below. Appropriate culture and susceptibility tests should be done before treatment in order to isolate and identify organisms causing infection and to determine their susceptibility to penicillin G. […]
On the market
- Earliest approval on file
- June 25, 1990
- Generic labelers
- 8 labelers
- Pharmacy cost
- Not in the survey
Supply and safety
- Shortage
- No current entry
- Recalls
- 1
Source: FDA drug labels via openFDA (Ampicillin label of February 21, 2025, Penicillin g label of September 16, 2020); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do ampicillin and penicillin g differ on the record?
Both are in FDA's class penicillin-class antibacterials.
Half-life, in each label's words: Ampicillin, “Due to maturational changes in renal function, ampicillin half-life decreases as postmenstrual age (a sum of …”; Penicillin g, “The mean beta-phase serum half-life of penicillin G administered by the intravenous route in ten patients with normal …”
Generics: ampicillin since 1971; penicillin g since 1947 (Drugs@FDA).
| Ampicillin | Penicillin g | |
|---|---|---|
| Labeled for | Bacterial infections, Urinary tract infections | Bacterial infections |
| Pharmacologic class | Penicillin-class Antibacterial | Penicillin-class Antibacterial |
| How it works (label) | n/a | n/a |
| Half-life (label) | Due to maturational changes in renal function, ampicillin half-life decreases as postmenstrual age (a sum of gestational age and postnatal age) increases for infants with postnatal age of less than 28 days. | The mean beta-phase serum half-life of penicillin G administered by the intravenous route in ten patients with normal renal function was 42 minutes, with a range of 31 to 50 minutes. |
| Earliest approval on file (Drugs@FDA) | December 29, 1966 | June 25, 1990 |
| First generic approved | March 3, 1971 | February 6, 1947 |
| Generic labelers (NDC) | 17 labelers | 8 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.441 per capsule (Ampicillin 500 mg capsule) | n/a |
| 12-month price change | -8% | n/a |
| Boxed warning | No | No |
| Shortage now | A presentation being discontinued | No current entry |
| Recalls recorded | 3 | 1 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 8,240 | 3,439 |
| DEA schedule | none | none |
Source: Drugs@FDA, FDA NDC Directory, CMS NADAC of October 7, 2026, FDA shortages and recalls, FAERS via openFDA (FDA files October 8, 2026)
What next?
- Alternatives to ampicillin
- every medicine labeled for the same conditions