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- For grand mal and partial seizures;
- Adult active siez:18-20mg/kg IV (50mg/min maximum infusion rate);
- Oral loading: 15-20mg/kg in doses of 400mg or less at 4 hr intervals;
- Maintainance doses: 300-400 mg/24 hr IV/PO divided q12-24 hr, based on plasma values and clinical response;
- ...or try: Loading dose 750 mg to 1 gm given IV over 1 hr; then supplemental doses of 100 mg 3-4 times qd;
- Note: Phenytoin may be injected directly via NS IV at rate no faster than 25-50 mg/min, or as infusion (add the loading dose to 100 ml 
NS) at rate < 25-50 mg/min;
- Note: IV must be in NS, do NOT use D5W IV saline;
- Note: Not compatable with Valium in the same IV site;
- Note cardiac depression, nystagmus, and ataxia as signs of toxicity;
- Contraindications: Sinus bradycardia, AV block greater then first degree, sinoatrial block, Strokes Adams symdrome;
- Don't use for siezures secondary to hypoglycemia or other metabolic causes;
- Discontinue phenytoin if patient develops skin rash;
- Use with caution in elderly patients and in patients with impaired liver fx
- Continuous monitoring of ECG and BP is necessary when administering IV Phenytoin loading dose (Beware: Hypotension);
- Phenytoin serum levels are affected by manycommon drugs (e.g. increased levels may be seen with concomitant use of cimetidine, dicumarol, salicylates, sulfonamides, tolbutamide, diazepam);
- Side Effects: Lymphadenopathy, Splenomegaly;
- Peds: Actively seizing: 15-20 mg/kg IV (10-25 mg/min max infusion rate) or oral loading dose as Adult;
       Maintenance: 4-8 mg/kg/day IV or PO divided q12hr/qd (usually q12hr);
       - try 0.5 to 1.5 mg/kg/min loading, then 4 to 7 mg/kg/day maintance;
- supp: cap 30, 100 mg, tab 50 mg

Bone changes induced by diphenylhydantoin in chicks on a controlled vitamin D intake.