Phenytoin- Pharmacology and popular brands

Phenobarbital, phenytoin, and valproate are widely used to treat Generalized Tonic-Clonic Seizures. However, each of these drugs is associated with dose-related and idiosyncratic adverse effects, and monitoring of hematological and hepatic function is routinely not advised.

Category of DrugPhenytoin is a Anticonvulsants/Antiepileptics
Mechanism of ActionPhenytoin promotes or decreases Na+ influx from membranes in motor cortex neurons; stabilizes neuronal membrane.
Chemical Structure Phenytoin.png
Molecular details Molecular Formula- C15H12N2O2
Molecular Weight- 252.27 g/mol
IUPAC Name5,5-diphenylimidazolidine-2,4-dione
IndicationsPhenytoin is used for
1. Generalized tonic-clonic seizures
2. Partial seizures
3. Status epilepticus.
Well Known
Pharmaceutical Brands
Available dosage forms1. TABLETS
Phenytoin Ikapharmindo Full Prescribing Information, Dosage & Side Effects  | MIMS Indonesia
TABLETS 2, 5 and 10 mg; CAPSULE 10 mg;
SUSPENSION 2 mg/ml; INJECTION 2 ml; ampoule (5 mg/ml).
DoseAdults- 18 mg/kg (do not exceed 50 mg/min as a loading dose);
maintenance dose -100 mg 6 to 8 hours.
Storage conditions Store protected from moisture at a temperature not exceeding 30⁰C
Pharmacokinetic properties 1. Phenytoin is completely absorbed.
2. Peak plasma concentration- 1.5-3 hours.
3. Vd-0.75 L/kg.
4. Protein binding- 90%
5. Phenytoin is extensively metabolized.
6. The majority is excreted as inactive metabolites
7. Half-life- 7 to 42 hours.
Contraindications1. Porphyria
2. Avoid parenteral use in sinus bradycardia
3. Sino-atrial block
4. Second- and
5. Third-degree heart block
6. Stokes-Adams syndrome
7. Pregnancy
Precautions1.  Hepatic impairment
2. lactation
3. Diabetes Mellitus
4. Monitor blood counts
5. Hypotension and heart failure
6. Intravenous administration-resuscitation facilities must be available
7. Injection solution alkaline
8. Interactions
Adverse Effects 1. Gastric intolerance
2. Headache
3. Sleeplessness
4. sedation
5. hallucinations
6. confusion
7. blurred vision
8. ataxia
9. nystagmus
10. diplopia
11. Slurred speech
12. cerebellar-vestibular symptoms,
Pregnancy Category D


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