Two medicines, side by side
Doxycycline vs metronidazole
Doxycycline and metronidazole are both labeled for bacterial infections. Drugs@FDA records approvals of doxycycline since 1967 and of metronidazole since 1963. Pharmacies paid $0.118 per doxycycline hyclate 100 mg tablet and $0.102 per metronidazole 250 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. Metronidazole's other strengths are brand-only: $2.60 per mL (Likmez 500 mg/5 mL suspension). In FDA's classes, doxycycline is a tetracycline-class drug and metronidazole a nitroimidazole antimicrobial.
Check it at the source: the doxycycline FDA label on DailyMed (effective July 25, 2025); the metronidazole FDA label on DailyMed (effective September 3, 2024).
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
Highlights of the metronidazole record
Metronidazole (Flagyl) · label of September 3, 2024
Metronidazole has been shown to be carcinogenic in mice and rats (see PRECAUTIONS ). Unnecessary use of the drug should be avoided. Its use should be reserved for the conditions described in the INDICATIONS AND USAGE section below.
Used for
From the label: indicationsSymptomatic Trichomoniasis. Metronidazole tablets are indicated for the treatment of T. vaginalis infection in females and males when the presence of the trichomonad has been confirmed by appropriate laboratory procedures (wet smears and/or cultures). Asymptomatic Trichomoniasis. […]
On the market
- Earliest approval on file
- July 18, 1963
- Generic labelers
- 55 labelers
- Pharmacy cost
- $0.102 per tablet
Supply and safety
- Shortage
- In shortage
- Recalls
- 7
Source: FDA drug labels via openFDA (Doxycycline label of July 25, 2025, Metronidazole label of September 3, 2024); NDC Directory, Drugs@FDA, NADAC, FDA shortages and recalls (October 8, 2026)
How do doxycycline and metronidazole differ on the record?
In FDA's classes, doxycycline is a tetracycline-class drug and metronidazole a nitroimidazole antimicrobial.
Half-life, in each label's words: 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 …”; Metronidazole, “The elimination half-life, measured during the first 3 days of life, was inversely related to gestational age.”
Only the metronidazole label carries a boxed warning.
Generics: doxycycline since 1973; metronidazole since 1984 (Drugs@FDA).
| Doxycycline | Metronidazole | |
|---|---|---|
| Labeled for | Urinary tract infections, Bacterial infections, Acne | Bacterial infections |
| Pharmacologic class | Tetracycline-class Drug | Nitroimidazole Antimicrobial |
| How it works (label) | n/a | n/a |
| Half-life (label) | 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 (± … | The elimination half-life, measured during the first 3 days of life, was inversely related to gestational age. |
| Earliest approval on file (Drugs@FDA) | December 5, 1967 | July 18, 1963 |
| First generic approved | June 18, 1973 | December 6, 1984 |
| Generic labelers (NDC) | 83 labelers | 55 labelers |
| Pharmacy cost (NADAC, each one's most listed form; strengths differ) | $0.118 per tablet (Doxycycline hyclate 100 mg tablet) | $0.102 per tablet (Metronidazole 250 mg tablet) |
| 12-month price change | -2% | +10% |
| Boxed warning | No | Yes |
| Shortage now | A presentation being discontinued | In shortage |
| Recalls recorded | 19 | 7 |
| FAERS reports (a report is not proof of cause; counts follow how widely a medicine is used) | 69,571 | 63,553 |
| 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 doxycycline
- every medicine labeled for the same conditions