Phenytoin Flashcards
What are indications for phenytoin use?
- Control of status epilepticus
- Reduce frequency of generalised/focal seizures - third line
How does phenytoin work?
Reduces neuronal excitability and electrical conductant amoung brain cells, which inhibits the spread of seizure activity by binding to Na+ channels in the inactive state, prolonging this inactivity and preventing NA+ influx into the neuron
What are side effects of phenytoin?
- Skin coarsening
- Hirsuitism
- Acne
- Gum hypertrophy
- Cerebellar toxicity
- Haematological disorders
- Osteomalacia
- Hypersensitivity
- Toxicity
What problems can phenytoin cause in preganancy?
Teratogenic - foetal hydantoin syndrome
Is phenytoin a cytochrome 450 inhibitor or inducer?
P450 inducer
What is meant by phenytoin being metabolised by the liver with zero order kinetics above the therapeutic range
At a constant rate irrespective of plasma concentration
What should be discussed in women of childbearing age who are on phenytoin?
Discuss treatment with specialist and folic acid adminstration
What are plasma phenytoin concentrations increased by?
- Overadminstration
- Cytochrome P450
What is the loading dose for phenytoin in status epilepticus?
20mg/kg - max dose 2g
What is the maintenance dose of phenytoin used in status epilepticus?
100mg every 6-8 hours
What should be done when adminstering IV phenytoin to prevent venous irritation?
Pre and post flush with 0.9% saline
What monitoring would you perform if using phenytoin?
- Plasma concentrations
- IV administration - BP, RR, SpO2
