7858430
Description
Mind Map by Carly Doolan, updated more than 1 year ago
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Created by Carly Doolan
almost 8 years ago
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Phenytoin
- MOA: Phenytoin sodium is a hydantoin derivative
anticonvulsant. It alters sodium flow in the motor cortex
reducing neuronal excitability and the conduction of
electrical activity.
- The onset of action after IV administration is
30-60minutes and the effect persists up to 24 hours.
Phenytoin is 90% and free phenytoin levels may be
altered in those with hypoalbuminaemia, ureamia,
after acute trauma and in pregnancy. protein bound
- AVE:hypotension, cardiac arrhythmia if too fast. Common signs of toxicity=nystagmus, ataxia, slurred
speech, decreased coordination, lethargy, mental confusion. Headaches, nausea, vomiting,
constipation., Skin rash, haemopoetic complications( thrombocytopenia) Local
iiritation,thrombophlebitis, inflammation,necrosis, purple glove syndrome,Dyskineasias =dystonia,
tremor, asterixis.
- Phenytoin levels may be potentiated or decreased by by carbamazepine,
phenobarbitone, sodium valproate,diazepam. Acute ETOH intake.
- Phenytoin levels can be potentiated by diazepam, methylphenidate,
omeprazole, erythromycin, antifunga agents,warfarin, isoniazid,
phenothiazines, ranitidine , azoles.
- Phenytoin levels may be decreased by calcium, rifampicin,
theophylline,methotrexate.
- Phenytoin levels may be decreased by calcium, rifampicin,
theophylline,methotrexate.
- Phenytoin levels can be potentiated by diazepam, methylphenidate,
omeprazole, erythromycin, antifunga agents,warfarin, isoniazid,
phenothiazines, ranitidine , azoles.
- Interactions: Increases the effects of warfarin,
TCAs,tramadol, MAOIs.
- The onset of action after IV administration is
30-60minutes and the effect persists up to 24 hours.
Phenytoin is 90% and free phenytoin levels may be
altered in those with hypoalbuminaemia, ureamia,
after acute trauma and in pregnancy. protein bound
- Narrow therapeutic index!!!!!
- Indications: Tx status epilepticus: tonis
clonic psychomotor seizures.
Prevention of seizures during or
following neurosurgery.
- Status Epilepticus dosage: Elderly >65years, low albumin:
loading dose=15mg/kg max rate 50mg/min maintenance
100mg Q6-8Hrly according to response and phenytoin levels.
Other adults= 20mg/kg max rate 50mg/min, followed by
maintenance PO OD.
- Phenytoin comes in different formulations- Capules (phenytoin sodium 30mg and
100mg), tablet(infatabs) (phenytoin 50mg), suspension (phenytoin 30mg in 5ml),
injection (phenytoin sodium 50mg/ml)
- Converting oral to IV dose: 1:1 conversion -capsules: IV,,,0.92:1 infatabs/suspension:IV
- Usual daily dose range= 200-500mg
- Usual daily dose range= 200-500mg
- Intermittent IV infusion:
- Must be completed within 1 hour when diluted using a 0.22micron inline filter
- Must be completed within 1 hour when diluted using a 0.22micron inline filter
- IV phenytoin is alkaline and irritant. Use large vein ad large bore needle, follow with a 20ml 0.9%
NaCl flush, Give slwoly max 50mg/min rapid administration can cause bradycardia, ypotension,
asystole,arrhythmias.
- Dilute with 0.9% NaCl only
- Do not mix with other meds even at luer site.
- Dilute with 0.9% NaCl only
- Converting oral to IV dose: 1:1 conversion -capsules: IV,,,0.92:1 infatabs/suspension:IV
- Phenytoin comes in different formulations- Capules (phenytoin sodium 30mg and
100mg), tablet(infatabs) (phenytoin 50mg), suspension (phenytoin 30mg in 5ml),
injection (phenytoin sodium 50mg/ml)
- Status Epilepticus dosage: Elderly >65years, low albumin:
loading dose=15mg/kg max rate 50mg/min maintenance
100mg Q6-8Hrly according to response and phenytoin levels.
Other adults= 20mg/kg max rate 50mg/min, followed by
maintenance PO OD.
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