Therapeutic Handbook - GGC Prescribing

Guideline for Phenytoin Dose Calculations1. Initial loading dose of phenytoin for status epilepticusIf the patient has not already received phenytoin then give:Phenytoin sodium IV 18 mg/kg (see Table 1).Ensure ECG, blood pressure and respiratory function are monitored throughout the duration of theinfusion.Table 1 – IV phenytoin loading doseWeight (kg)IV Loading Dose (mg)Volume of IV phenytoin (ml)(vial = 250 mg/5ml)35 - 44 700 1445 - 54 900 1855 - 64 1100 2265 - 74 1250 2575 - 84 1450 2985 - 94 1600 32> 94 1800 36Central Nervous SystemPhenytoin IV administration• Give phenytoin over 30 - 40 minutes (rate < 50 mg/minute). In patients who are elderly, or havepre-existing cardiac disease, give phenytoin over 60 - 80 minutes (rate < 25 mg/minute).• Ideally, administer undiluted via a syringe pump through a large gauge needle or IV catheter intoa large forearm vein.• If dilution is essential, mix with 100 - 250 ml sodium chloride 0.9% to a final concentration of< 10 mg/ml, and administer by infusion pump.• Use the solution immediately, ideally with a 0.2 - 0.5 micron in-line filter.• To avoid local venous irritation, inject sterile sodium chloride 0.9% through the vein or catheterbefore and after each phenytoin infusion.• Do not administer as a continuous infusion.Phenytoin ‘Top-up’ loading dose continues on next pagePage 192