PHENYTOIN (Dilantin)

Name:	PHENYTOIN (Dilantin^R)
Classification:	*anticonvulsant; antiarrhythmic* treatment or prophylaxis of tonic-clonic seizures management of status epilepticus treatment of ventricular tachycardia and paroxysmal tachycardia especially secondary to digoxin toxicity
Dose:	Loading Dose: 14-18mg/kg IV direct Maintenance Dose: 5mg/kg/day (in divided doses every 8 hours)
Administration:	IV Direct: preferred route of administration; rate not to exceed 50mg/min IV Infusion: must be mixed in sodium chloride 0.9% or Ringer's Lactate; do not mix with dextrose solutions as precipitation will occcur concentration of 1-20mg/ml; rate not to exceed 50mg/min must be administered with a filter; a TPN set can be used and changed with the same frequency of other line changes *administer at slower rate if patient is receiving dopamine or in the presence of cardiovascular instability* IV line to be flushed with NS or RL before and after phenytoin administration use prepared solutions immediately
Adverse Effects:	hypotension decreased automaticity of ventricles in second and complete AV heart block (suppression of ventricular escape rhythm) hyperglycemia nystagmus folic acid deficiency; megaloblastic anaemia nausea seizures (abrupt withdrawal may precipitate peripheral neuropathy seizure) rash lymphadenopathy gingival hyperplasia
Drug Interactions:	phenytoin + dopamine = increased hypotension phenytoin + theophylline = decreased theophylline effect phenytoin + dexamethasone = decreased dexamethasone effect phenytoin + quinidine = decreased quinidine effect phenytoin + amiodarone = increased phenytoin level phenytoin + fluconazole = increased phenytoin level
Monitoring Therapy:	BP HR and rhythm seizure activity neurological signs phenytoin levels: therapeutic 40 - 80 uM/L (pre-dose), toxic > 80 uM/L (need to adjust for low serum albumin and/or high urea levels, which will increase the free fraction of phenytoin leading to an increased amount of drug available for activity) draw levels immediately before next scheduled dose, or at least 4-6 hours post administration
Adult Critical Care Protocol:	May be administered by IV infusion and titrated by a nurse in Adult Critical Care May be administered IV direct by a nurse in Adult Critical Care provided that the rate does not exceed 50 mg/min