PHENYTOIN (DILANTIN)

PHENYTOIN (DILANTIN)

CLASSIFICATION

� Anticonvulsants

INDICATIONS

� Grand mal/psychomotor seizures

 � Certain ventricular arrhytmias, (IE: digoxin induced V.T)

MODE OF ACTION

CNS -Na efflux from neurones is promoted, preventing hyperexcitability although it enhances conduction.

� PRECAUTIONS

� If given too quickly I.V -cause bradyarrhythmias atrial or ventricular fibrillation, sinoatrial block, 2nd and 3rd degree A-V block, Stokes Adams Syndrome.

� Risk of liver toxicity is increased in liver dysfunction, elderly, serious illness.

� should not be administered concurrently with Dopamine

ADVERSE REACTIONS

� CNS ataxia, nystagmus, dysarthria, confusion.

 � GIT nausea and vomiting

 � SKIN morbilliform rashes, bullous exfoliative lupus, Steven Johnson Syndrome

. � Blood dyscrasia

� Folate depletion

 � Ginival hypertrophy

 � Lymph node enlargement

� Hepatitis

 � Peripheral neuropathy.

DOSAGE AND ADMINISTRATION

ADULTS

RAPID I.V When therapeutic levels are needed rapidly (EG eclampsia, status epilepticus) give 250 mg I.V over 5 minutes. Repeat every 30 minutes until 4 such doses have been given.

SLOW I.V

The slow rate of administration I.V makes phenytoin less attractive than some of the more rapidly effective parental agents available for status epilepticus eg Clonazepam. Ideally should be infused over 15 - 30 minutes and must be mixed only in normal saline no other solution is compatible

FOR ARRHYTHMIAS

3 - 5 mg/kg at a rate not exceeding 50 mg/min . repeat if necessary.

ORAL

4 - 7 mg/kg /day in 2 divided doses; some patients will achieve levels in the therapeutic range on the lower dose, others require more.

PAEDIATRICS

10 - 20 mg/kg by slow I.V.I (max 1 - 3 mg/kg/min)

PRESENTATION

I.V 50 mg/ml (2 ml) and .50 mg/ml (5 ml) oral 30 mg and 100 mg tablets