Diphedan
Generic Name
Phenytoin Sodium
Manufacturer
The Searle Company Ltd.
Country
Pakistan
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Price Details
Current market pricing information
| Variant | Unit Price | Strip Price |
|---|---|---|
| diphedan 100 mg tablet | ৳ 2.01 | ৳ 20.10 |
Description
Overview of the medicine
Diphedan 100 mg Tablet contains Phenytoin Sodium, an anticonvulsant medication used to prevent and control seizures (fits) in people with epilepsy. It works by stabilizing electrical activity in the brain.
Uses & Indications
Dosage
Adults
Initial oral dose: 100 mg three times daily, adjusted according to plasma levels and response. Maintenance: 300-400 mg/day in 1-3 divided doses.
Elderly
Lower initial doses (e.g., 50 mg three times daily) and slower titration may be required due to altered pharmacokinetics and increased sensitivity.
Renal_impairment
No specific dosage adjustment needed for renal impairment, but careful monitoring and dose adjustment based on plasma levels are recommended, especially with hepatic dysfunction.
How to Take
Oral administration. Take with food to minimize gastrointestinal upset. Do not crush or chew extended-release tablets. Maintain consistent dosing schedule.
Mechanism of Action
Phenytoin works primarily by blocking voltage-gated sodium channels in neurons, thereby inhibiting the rapid firing of action potentials. This stabilizes the neuronal membrane and reduces the spread of seizure activity.
Pharmacokinetics
Onset
Therapeutic effects typically observed within hours to days for oral forms, depending on loading dose. IV onset is minutes.
Excretion
Mainly renal excretion of inactive metabolites, with a small amount of unchanged drug excreted in urine and bile.
Half life
Dose-dependent, typically 7 to 42 hours (average 22 hours) in adults.
Absorption
Variable and often slow absorption after oral administration; bioavailability can differ between formulations.
Metabolism
Primarily hepatic via cytochrome P450 enzymes (CYP2C9 and CYP2C19) to inactive metabolites. It exhibits saturable (non-linear) pharmacokinetics.
Side Effects
Contraindications
- Hypersensitivity to phenytoin or other hydantoins
- History of acute hepatic porphyria
- Sinus bradycardia, sinoatrial block, second or third degree AV block, Adams-Stokes syndrome (especially IV form)
Drug Interactions
Alcohol
Acute intake can increase phenytoin levels; chronic intake can decrease levels.
Valproate, cimetidine, fluconazole
Can increase phenytoin levels.
Carbamazepine, phenobarbital, rifampin
Can decrease phenytoin levels.
Oral contraceptives, warfarin, corticosteroids
Phenytoin can decrease the effectiveness of these drugs.
Storage
Store below 30°C in a dry place, away from light and moisture. Keep out of reach of children.
Overdose
Symptoms include nystagmus, ataxia, dysarthria, tremor, hyperreflexia, lethargy, slurred speech, blurred vision, nausea, vomiting, coma. Management is supportive, including gastric lavage or activated charcoal for recent ingestion. Monitor vital signs and phenytoin levels.
Pregnancy & Lactation
Pregnancy Category D. Associated with fetal hydantoin syndrome. Discuss risks/benefits with a doctor. Excreted in breast milk; generally not recommended during breastfeeding.
Side Effects
Contraindications
- Hypersensitivity to phenytoin or other hydantoins
- History of acute hepatic porphyria
- Sinus bradycardia, sinoatrial block, second or third degree AV block, Adams-Stokes syndrome (especially IV form)
Drug Interactions
Alcohol
Acute intake can increase phenytoin levels; chronic intake can decrease levels.
Valproate, cimetidine, fluconazole
Can increase phenytoin levels.
Carbamazepine, phenobarbital, rifampin
Can decrease phenytoin levels.
Oral contraceptives, warfarin, corticosteroids
Phenytoin can decrease the effectiveness of these drugs.
Storage
Store below 30°C in a dry place, away from light and moisture. Keep out of reach of children.
Overdose
Symptoms include nystagmus, ataxia, dysarthria, tremor, hyperreflexia, lethargy, slurred speech, blurred vision, nausea, vomiting, coma. Management is supportive, including gastric lavage or activated charcoal for recent ingestion. Monitor vital signs and phenytoin levels.
Pregnancy & Lactation
Pregnancy Category D. Associated with fetal hydantoin syndrome. Discuss risks/benefits with a doctor. Excreted in breast milk; generally not recommended during breastfeeding.
Frequently Asked Questions
Common questions about this medicine
Pack Sizes
Shelf Life
Typically 2-3 years from manufacturing date
Availability
Pharmacies, hospitals
Approval Status
Approved in many countries, including FDA
Patent Status
Generic available (off-patent)
WHO Essential Medicine
YesClinical Trials
Extensively studied since its introduction. Ongoing trials focus on pharmacogenomics, specific populations, and comparative efficacy/safety against newer AEDs.
Lab Monitoring
- Phenytoin plasma levels (therapeutic range: 10-20 mcg/mL)
- Complete blood count (CBC)
- Liver function tests (LFTs)
- Renal function tests
- Serum albumin
- Folic acid levels
- Vitamin D levels
Doctor Notes
- Individualize dose based on clinical response and serum levels.
- Monitor for signs of hypersensitivity, especially skin reactions.
- Counsel patients on adherence and importance of not stopping abruptly.
Patient Guidelines
- Take medicine exactly as prescribed.
- Do not stop taking phenytoin abruptly, as this can lead to increased seizure frequency or status epilepticus.
- Report any skin rash, fever, or swollen glands to your doctor immediately.
- Maintain good oral hygiene to prevent gingival hyperplasia.
Missed Dose Advice
If a dose is missed, take it as soon as you remember, unless it is almost time for the next dose. Do not double the dose. Contact your doctor if you miss several doses.
Driving Precautions
May cause dizziness, drowsiness, or blurred vision. Avoid driving or operating machinery until you know how this medication affects you.
Lifestyle Advice
- Avoid alcohol consumption.
- Ensure adequate intake of folic acid and vitamin D, as phenytoin can deplete these.
- Regular exercise and a balanced diet are recommended.
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