Two medicines, side by side
Ampicillin vs cefazolin
Ampicillin and cefazolin are both labeled for urinary tract infections. Drugs@FDA records approvals of ampicillin since 1966 and of cefazolin since 1973. Pharmacies paid $0.441 per ampicillin 500 mg capsule and $1.07 per cefazolin 1 g vial (NADAC, October 7, 2026); the strengths differ, so the two prices are not like for like. In FDA's classes, ampicillin is a penicillin-class antibacterial and cefazolin a cephalosporin antibacterial.
Check it at the source: the ampicillin FDA label on DailyMed (effective February 21, 2025); the cefazolin FDA label on DailyMed (effective May 14, 2026).
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 cefazolin record
Cefazolin (Ancef) · label of May 14, 2026
Used for
From the label: indicationsCefazolin for Injection, USP is indicated in the treatment of the following serious infections due to susceptible organisms: Respiratory Tract Infections: Due to S. pneumoniae, Klebsiella species, H. influenzae, S. aureus (penicillin-sensitive and penicillin-resistant), and group A beta-hemolytic streptococci. […]
On the market
- Earliest approval on file
- October 4, 1973
- Generic labelers
- 15 labelers
- Pharmacy cost
- $1.07 per vial
Supply and safety
- Shortage
- No current entry
- Recalls
- 10
Source: FDA drug labels via openFDA (Ampicillin label of February 21, 2025, Cefazolin label of May 14, 2026); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do ampicillin and cefazolin differ on the record?
In FDA's classes, ampicillin is a penicillin-class antibacterial and cefazolin a cephalosporin antibacterial.
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 …”; Cefazolin, “The serum half-life for Cefazolin for Injection is approximately 1.8 hours following IV administration and …”
Generics: ampicillin since 1971; cefazolin since 1973 (Drugs@FDA).
| Ampicillin | Cefazolin | |
|---|---|---|
| Labeled for | Bacterial infections, Urinary tract infections | Urinary tract infections |
| Pharmacologic class | Penicillin-class Antibacterial | Cephalosporin Antibacterial |
| How it works (label) | n/a | Mechanism of Action Cefazolin is a bactericidal agent that acts by inhibition of bacterial cell wall synthesis. |
| 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 serum half-life for Cefazolin for Injection is approximately 1.8 hours following IV administration and approximately 2 hours following IM administration. |
| Earliest approval on file (Drugs@FDA) | December 29, 1966 | October 4, 1973 |
| First generic approved | March 3, 1971 | November 2, 1973 |
| Generic labelers (NDC) | 17 labelers | 15 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.441 per capsule (Ampicillin 500 mg capsule) | $1.07 per vial (Cefazolin 1 g vial) |
| 12-month price change | -8% | +10% |
| Boxed warning | No | No |
| Shortage now | A presentation being discontinued | No current entry |
| Recalls recorded | 3 | 10 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 8,240 | 11,982 |
| 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