metronidazole vs phenytoin
Side-by-side comparison of metronidazole and phenytoin. Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
minor Known Drug Interaction
Drugs that Induce CYP450 Enzymes The simultaneous administration of drugs that induce microsomal liver enzymes, such as phenytoin or phenobarbital, may accelerate the elimination of metronidazole, resulting in reduced plasma levels; impaired clearance of phenytoin has also been reported.
Recommendation: Your doctor should monitor your blood levels closely because both medications may need dosage adjustments to work safely and effectively.
Flagyl
Dilantin
Metronidazole is an antibiotic medicine. It fights bacteria and certain parasites in your body.
Phenytoin injection is used to treat certain types of seizures. It can also prevent seizures during or after neurosurgery.
Metronidazole treats infections like trichomoniasis, amebiasis, and certain anaerobic bacterial infections. Trichomoniasis is a sexually transmitted infection. Amebiasis includes infections of the intestines and liver. Anaerobic bacteria cause infections inside the abdomen, on the skin, and in the female reproductive system.
This medicine treats generalized tonic-clonic status epilepticus, a type of prolonged seizure. It also helps prevent and treat seizures that may happen during or after brain surgery. Sometimes, it can be used for a short time instead of the oral form of phenytoin when you cannot take the medicine by mouth.
Metronidazole works by entering the bacteria or parasite and damaging its DNA. This damage stops the bacteria or parasite from growing and multiplying. Eventually, the infection is cleared.
Phenytoin works by slowing down the signals in the brain that cause seizures. It stabilizes nerve cell membranes, reducing excessive electrical activity. This helps to prevent seizures from starting or spreading.
- • Nausea
- • Headache
- • Loss of appetite
- • Vomiting
- • Diarrhea
No common side effects listed.
- Nausea 4,691
- Diarrhoea 4,116
- Vomiting 3,283
- Pyrexia 3,224
- Drug Hypersensitivity 3,138
- The medicine is reacting with another medicine 1,547
- Seizure 1,382
- Poisoning from different substances 1,353
- Convulsion 1,260
- Prolonged seizure 790
Metronidazole can cause cancer in mice and rats. Only use it for the conditions listed in this leaflet. Do not drink alcohol or use products with propylene glycol while taking this medicine, and for 3 days after.
This medicine can cause serious heart problems if given too quickly. The injection rate should not be faster than 50 mg per minute for adults, and 1 to 3 mg/kg/min (or 50 mg per minute, whichever is slower) for children. Your heart will be monitored closely during and after the injection.
Do not take metronidazole during the first three months of pregnancy. Talk to your doctor if you are pregnant or breastfeeding before taking this medicine.
Taking phenytoin during pregnancy may increase the risk of birth defects. If you are pregnant or plan to become pregnant, talk to your doctor about the risks and benefits of this medicine.
How to Read This metronidazole vs phenytoin Comparison
metronidazole is classified in the Nitroimidazole Antibiotic drug class, while phenytoin sits within the Anticonvulsant (Hydantoin) class. Drugs from different classes work through distinct mechanisms, so a head-to-head comparison illustrates trade-offs rather than equivalence. Both drugs are prescription-only, so a licensed provider must authorize use.
Adverse event totals above are pulled from the FDA's Adverse Event Reporting System (FAERS). For these top-ranked reactions alone, metronidazole has 18,452 submissions while phenytoin has 6,332. Those figures reflect cumulative reporting volume, not per-patient risk, so older, widely dispensed drugs typically look worse on count alone. These two drugs have a known minor interaction flagged in FDA labeling, attributed to phenytoin makes your liver clear metronidazole out of your body too quickly, while metronidazole can cause phenytoin to build up to unsafe levels.. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.
A table cannot substitute for clinical judgment. Effectiveness, tolerability, drug-drug interactions with your other medications, kidney and liver function, pregnancy status, insurance formulary, and price all feed into a decision that only a licensed prescriber can make responsibly. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This page is for educational purposes only, is not medical advice, and should not be used to self-switch between metronidazole and phenytoin - always consult your physician or pharmacist first.
Important: This comparison is for informational purposes only. Drug effects vary between individuals. Always consult your doctor or pharmacist for personalized medical advice.