Phenytoin Sodium Injection USP

Description

Phenytoin Sodium Injection is available in 50mg/ml – 2ml Inj

Indication

Epilepsy

Status epilepticus

Neuropathic pain

Choreoathetosis

Myotonia

Arrhythmias where first line treatment not effective

Tetralogy of Fallot – post operative

Dosage

IV Dose for Seizures

Do not exceed the infusion rate of 50mg/min

Loading dose – 10 to 15mg/kg IV slowly

Maintenance dose – 100mg IV every 6 to 8 hours

IM Dose

Avoid the IM route due to erratic absorption

IV Dose for Arrhythmias

1.25 mg/kg IV every 5 minutes

IV Dose for status Epilepticus

Loading Dose – 15 to 20mg/kg by slow IV administration (at a rate not exceeding 50mg/minute)

Maintenance Dose – 100mg 6 to 8 hours

Uses

To treat

Convulsions (Control seizures)

Tonic – clonic (grandma seizures)

Psychomotor (Temporal lobe seizures)

Contraindications

Known hypersensitivity to hydantion products. Because of its effect on ventricular automaticity, IV phenytoin is contraindicated in sinus bradycardia, sinoatrial block, second and third degree AV block, patients with Adams strokes syndrome

Adverse Drug Reaction

Fatigue

Irritability

Headache

Nystagmus

Ataxia

Dyskinesia

Lethargy

Slurred Speech

Vertigo

Gum hypertrophy

Hirsutism

Osteomalacia

Coarse facies

Cognitive dysfinction

Folate deficiency

Drug Interaction

Amiodarone, Chloramphenicol, Cimetidine, Disulfiram, Erythromycin, Fluconazole, Fluoxetine, Isoniazid, Ketoconazole, Methylphenidate, Omeprazole, Phenylbutazone, Salicylates, Sulfonamides, Trazodone, Warfarin and Acute alcohol ingestion – Drugs may increase Phenytoin serum levels

Carbmazepine, Chronic Alcohol Abuse, Diazoxide, Rifampicin and Theophylline – Drugs may decrease phenytoin levels

Phenobarbital, Valporic acid and Sodium Valporate – Drugs may either increase or decrease Phenytoin serum levels

Corticosteroids, Diazoxide, Digitalis glycosides, Doxycycline, Estrogens, Furosemide, Levodopa, Methadone, Oral Contraceptives, Quinidine, Theophylline, Vitamin D and warfarin, Drug efficacy may impaired by Phenytoin

Mechanism of Action

Phenytoin is an anticonvulsant which elevates the seizure threshold in the motor cortex by limiting the post tetanic potentiation (PTP) of synaptic transmission. It exerts this effect by preventing the excessive accumulation of intracellular sodium during tetanic stimulation by either reducing the passive influx of sodium or increasing the efficiency of the sodium pump