Hydantoins

Hydantoins:
• eg phenytoin, ethotoin, felbamate, mephenytoin, fosphenytoin
• usually used as the first line drug for tonic-clonic (grand mal) seizures and complex partial seizures. Phenytoin also used for arrhythmias
• inhibits impulse by slowing recovery of sodium channels from their inactive to active state  inhibits entry of sodium into neuron  suppression of action potential  limits propagation of seizures
• only affects neurons that are hyperactive – does not affect “healthy” neurons
• phenytoin is absorbed slowly, but rapidly distributed; mephenytoin is rapidly absorbed
• substantial variability between individuals in the absorption and metabolism
• adverse effects – if dose high, get CNS effects (drowsiness, tremor, nystagmus, sedation, ataxia, diplopia, cognitive impairment); swelling and tenderness of gums; measles like skin rash

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