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Phenytoin - Na channel



               blocker class IB

                   •  Taken Oral and IV
               Mech: Na+ channel blocker 

               ↓ Ventricular automaticity -
               AV-conduction. (C.I. in atrial fibrillation & atrial flutter).

               Adverse effects:
               Gingival hyperplasia, Ataxia, Nystagmus & sedation


               Therapeutic uses


                   1) Antiepileptic
                   2) 2nd chice for ttt of digoxin toxicity


               CI.

                   •  atrial fibrillation & atrial flutter
               Precautions and interaction


                       1) Phenytoin → ↑LME → ↑ metabolism of oral contraceptives &
                          anticoagulants

                       2) Isoniazide, cimetidine, Alcohol, diazepam→ ↓ LME → ↑ serum
                          phenytoin (↑ toxicity)
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