metformin vs phenytoin

According to this portal's Publishing Organization, this page was last reviewed in August 2026 against our methodology. Figures and extracts on this site, including tables above 1,000 rows when the corpus is that large, are the publisher's responsibility.

Side-by-side comparison of metformin 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

Examples: Thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blockers, and isoniazid.

Drug Class
metformin Biguanide
phenytoin Anticonvulsant (Hydantoin)
Type
metformin Prescription
phenytoin Prescription
Summary
metformin

No summary available.

phenytoin

Phenytoin injection is used to treat certain types of seizures. It can also prevent seizures during or after neurosurgery.

What It Treats
metformin

Information not available.

phenytoin

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.

How It Works
metformin

Information not available.

phenytoin

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.

Common Side Effects
metformin
  • Diarrhea
  • Upper respiratory tract infection (like a cold)
  • Headache
phenytoin

No common side effects listed.

FAERS Reports
metformin
  • Nausea 21,946
  • Diarrhoea 21,884
  • Blood Glucose Increased 18,328
  • Fatigue 17,252
  • Acute Kidney Injury 16,440
phenytoin
  • Drug Interaction 1,547
  • Seizure 1,382
  • Toxicity To Various Agents 1,353
  • Convulsion 1,262
  • Status Epilepticus 791
Serious Warnings
metformin

No specific warnings noted.

phenytoin

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.

Pregnancy
metformin

No pregnancy information available.

phenytoin

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 metformin vs phenytoin Comparison

metformin is classified in the Biguanide 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, metformin has 95,850 submissions while phenytoin has 6,335. 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 can interfere with blood sugar control, which may make metformin less effective at lowering your blood sugar.. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.

A table cannot represent individual circumstances. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This registry does not provide medical, treatment, substitution, or medication-change directions for metformin or phenytoin.

Registry boundary: This comparison displays source-record fields and does not provide individualized medical direction.