DESCRIPTION-
Fosphenytoin is a water-soluble phenytoin prodrug used only in hospitals for the treatment of epileptic seizures. It works by slowing down impulses in the brain that cause seizures. Its main mechanism is to block frequency-dependent, use-dependent and voltage-dependent neuronal sodium channels, and therefore limit repetitive firing of action potentials.
PHARMACODYNAMIC-
Fosphenytoin is a water-soluble phenytoin prodrug used only in hospitals for the treatment of epileptic seizures. Following parenteral administration of fosphenytoin, fosphenytoin is converted to the anticonvulsant phenytoin by endogenous phosphatases. For every mmol of fosphenytoin administered, one mmol of phenytoin is produced. The pharmacological and toxicological effects of fosphenytoin include those of phenytoin.
MECHANISM OF ACTION –
Posphenytoin is a prodrug of phenytoin and accordingly, its anticonvulsant effects are attributable to phenytoin. Phenytoin acts on sodium channels on the neuronal cell membrane, limiting the spread of seizure activity and reducing seizure propagation. By promoting sodium efflux from neurons, phenytoin tends to stabilize the threshold against hyperexcitability caused by excessive stimulation or environmental changes capable of reducing membrane sodium gradient. This includes the reduction of post-tetanic potentiation at synapses. Loss of post-tetanic potentiation prevents cortical seizure foci from detonating adjacent cortical areas.
VOLUME OF DISTRIBUTION- 4.3 TO 10.8 L
HALF LIFE - 15 MINT
DRUG INTRACTION -
FOSPHYNTOIN + AMIODARONE - Fosphenytoin may increase the QTc-prolonging activities of Amiodarone.
FOSPHYNTOIN + ACENOCOUMAROL - Fosphenytoin may increase the anticoagulant activities of Acenocoumarol.
FOOD INTRACTION –
* Avoid alcohol.
* Do not take calcium, aluminum, magnesium or Iron supplements within 2 hours of taking this medication.
* Take with food.
REFERENCE-
Tripathi K.D,"Essentials of medical pharmacology",7th edition,page no- 415, 421, 424
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