Two medicines, side by side
Ampicillin vs doxycycline
Ampicillin and doxycycline are both labeled for bacterial infections and urinary tract infections. Drugs@FDA records approvals of ampicillin since 1966 and of doxycycline since 1967. Pharmacies paid $0.441 per ampicillin 500 mg capsule and $0.118 per doxycycline hyclate 100 mg tablet (NADAC, October 7, 2026); the strengths differ, so the two prices are not like for like. Doxycycline's other strengths are brand-only: $18.18 per Doryx mpc DR 60 mg tablet. In FDA's classes, ampicillin is a penicillin-class antibacterial and doxycycline a tetracycline-class drug.
Check it at the source: the ampicillin FDA label on DailyMed (effective February 21, 2025); the doxycycline FDA label on DailyMed (effective July 25, 2025).
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 doxycycline record
Doxycycline (Vibramycin) · label of July 25, 2025
Used for
From the label: indicationsTo reduce the development of drug-resistant bacteria and maintain effectiveness of doxycycline capsules and other antibacterial drugs, doxycycline capsules should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. […]
On the market
- Earliest approval on file
- December 5, 1967
- Generic labelers
- 83 labelers
- Pharmacy cost
- $0.118 per tablet
Supply and safety
- Shortage
- A presentation being discontinued
- Recalls
- 19
Source: FDA drug labels via openFDA (Ampicillin label of February 21, 2025, Doxycycline label of July 25, 2025); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do ampicillin and doxycycline differ on the record?
In FDA's classes, ampicillin is a penicillin-class antibacterial and doxycycline a tetracycline-class drug.
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 …”; Doxycycline, “1.62 0.95 0.37 0.15 (μg/mL) Average Observed Values Maximum Concentration 3.61 μg/mL (± 0.9 sd) Time of Maximum …”
Generics: ampicillin since 1971; doxycycline since 1973 (Drugs@FDA).
| Ampicillin | Doxycycline | |
|---|---|---|
| Labeled for | Bacterial infections, Urinary tract infections | Urinary tract infections, Bacterial infections, Acne |
| Pharmacologic class | Penicillin-class Antibacterial | Tetracycline-class Drug |
| 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. | 1.62 0.95 0.37 0.15 (μg/mL) Average Observed Values Maximum Concentration 3.61 μg/mL (± 0.9 sd) Time of Maximum Concentration 2.60 hr (± 1.10 sd) Elimination Rate Constant 0.049 per hr (± 0.030 sd) Half-Life 16.33 hr (± … |
| Earliest approval on file (Drugs@FDA) | December 29, 1966 | December 5, 1967 |
| First generic approved | March 3, 1971 | June 18, 1973 |
| Generic labelers (NDC) | 17 labelers | 83 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.441 per capsule (Ampicillin 500 mg capsule) | $0.118 per tablet (Doxycycline hyclate 100 mg tablet) |
| 12-month price change | -8% | -2% |
| Boxed warning | No | No |
| Shortage now | A presentation being discontinued | A presentation being discontinued |
| Recalls recorded | 3 | 19 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 8,240 | 69,571 |
| 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