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diazoxide vs phenytoin

Side-by-side comparison of diazoxide 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

Table 1: Drugs That Affect Phenytoin Concentrations Interacting Agent Examples Drugs that may increase phenytoin serum levels Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole trimethoprim Other Acute alcohol intake, amiodarone,...

Recommendation: Your doctor should monitor your phenytoin blood levels and may need to increase your dose.

Drug Class
diazoxide Potassium Channel Opener (Hyperinsulinism)
phenytoin Anticonvulsant (Hydantoin)
Type
diazoxide Prescription
phenytoin Prescription
Summary
diazoxide

VYKAT XR is a medicine used to treat excessive hunger in people with Prader-Willi syndrome. It helps to control their appetite.

phenytoin

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

What It Treats
diazoxide

VYKAT XR treats hyperphagia (excessive hunger) in people aged 4 years and older who have Prader-Willi syndrome (PWS). PWS is a genetic disorder that can cause constant hunger. This medicine helps manage the strong urge to overeat.

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
diazoxide

VYKAT XR contains diazoxide choline. It is thought to work by affecting how insulin is released in the body. This helps to reduce hunger.

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
diazoxide
  • Increased hair growth
  • Swelling
  • High blood sugar
  • Rash
  • Fever
phenytoin

No common side effects listed.

FAERS Reports
diazoxide
  • Low blood sugar 97
  • High blood sugar 45
  • The medicine is not working for a condition it's not approved for 38
  • The medicine is interacting with another medicine 30
  • Swelling in the arms or legs 25
phenytoin
  • The medicine is reacting with another medicine 1,547
  • Seizure 1,382
  • Poisoning from different substances 1,353
  • Convulsion 1,260
  • Prolonged seizure 790
Serious Warnings
diazoxide

VYKAT XR can cause high blood sugar, sometimes leading to a serious condition called diabetic ketoacidosis. Watch for signs like excessive thirst, frequent urination, and increased appetite with weight loss. This medicine can also cause fluid overload. Tell your doctor if you notice swelling or other signs of fluid retention.

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
diazoxide

It is not known if VYKAT XR can harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant. It is also not known if VYKAT XR passes into breast milk. Talk to your doctor about the best way to feed your baby if you are taking this medicine.

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 diazoxide vs phenytoin Comparison

diazoxide is classified in the Potassium Channel Opener (Hyperinsulinism) 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, diazoxide has 235 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 diazoxide can lower the amount of phenytoin in your blood, which might make your seizure medicine work less effectively.. 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 diazoxide 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.