Wk 32 - Epilepsy in practice: AEDs Flashcards
What is the dose for sodium valproate?
- initially 600mg daily divided 1-2 doses
- Inc 150-300mg every 3 days
- Maintenance: 1-2g daily
What are the common side effects of sodium valproate?
- Alopecia, tremor, weight gain, menstrual irregularities
- Hepatotoxicity, pancreatitis, blood disorders, SCARS
What are the effects of valproate as an enzyme inhibitor?
- Inc toxicity w/ lamotrigine, phenytoin, phenobarbital + carbamazepine
- Inc adverse effect w/ olanzapine
Give examples of an effect of other drugs on valproate
Carbapenems red conc valproate
What monitoring is required for sodium valproate?
- TDM - plasma valproate conc not useful index of efficacy tf routine monitoring unhelpful
- LFTs - before + during 1st 6 months
- FBC - before treatment + surgery
Outline the rules of sodium valproate in pregnancy
- Highly teratogenic: neurodevelopmental disorders + malformations
- Not used unless pregnancy prevention programme met + judged by specialist
What is the pregnancy prevention programme?
- Highly effective contraception: intrauterine, implant or barrier method
- Risk acknowledgement form: signed + up to date
- Annual review by specialist
- Refer to specialist if unplanned pregnancy or patient plans pregnancy
What is the dose for carbamazepine?
- Initially 100-200mg 1-2 times a day
- Inc 100-200mg every 2 weeks
- Usual dose: 0.8-1.2g daily in divided doses
- IR, MR, liquid + suppositories (max 1g)
What are the side effects of carbamazepines?
- Dizziness, drowsiness, ataxia
- Hyponatraemia
- Hepatotoxicity
- SCARS
- Leucopenia
- Thrombocytopenia
What drugs does carbamazepine have an effect on as an enzyme inducer?
- DOACS
- Warfarin
- COC
What are the effects when taking phenytoin + carbamazepine together?
- Carb inc phenytoin levels
- Phenytoin red conc carb
What inc concentration of carbamazepine?
- Clarithromycin
- Diltiazem
- Grapefruit juice
What dec concentration of carbamazepine?
- Phenytoin
- Rifampicin
- Theophylline
- St johns wort
What is the monitoring requirement pre-treatment of carbamazepine?
- FBC, U+E + LFTs
- Test HLA-B1502 in chinese + thai
- Test HLA-A 3101 in european + japanese
- Bc inc risk of stevens-johnsons syndrome
What is the monitoring requirements for carbamazepine?
- Plasma conc 4-12mg/l - measure after 1-2wks
- Not routinely monitored - only if toxic or non-compliance
- Trough level
What is the dose for phenytoin?
Inc increments of 25-50mg
- Initially 150-300mg OD
- Maintenance 200-500mg daily
- Tabs (sodium), chewable tabs (base), suspension (base), IV (sodium)
What are the side effects of phenytoin?
- Coarsening of facial features
- Gingival hyperplasia
- Bone marrow suppression
- Vit D deficiency, bone fractures
- Folate deficiency
- Hepatotoxicity
- Rash, SCARS
- Toxicity - nystagmus, diplopia, slurred speech, ataxia, confusion, + hyperglycaemia
Which drugs increase phenytoin concentrations?
- Clarithromycin
- Valproate
- Fluconazole
Which enzyme inducers red phenytoin levels?
- John’s wort
- Rifampicin
Which drugs can increase or decrease levels of phenytoin?
- Carbamazepine
- Ciprofloxacin
What are the monitoring requirements for phenytoin?
- HLAB 1502 in chinese + thai
- LFTs
- FBC
- U+E
- Trough level (5-7 days)
What is the loading dose for IV phenytoin?
20mg/kg
What is the maintenance dose for IV phenytoin + how is it administered + monitored?
- 100mg TDS
- 0.2 micron filter into large vein
- BP, RR + ECG
What is the dose for lamotrigine?
- 25mg OD for 14 days
- Inc 50mg OD for further 14 days
- Inc upto 100mg every 7-14 days
- Maintenance: 100-200mg daily in 1-2 divided doses
- Tabs, dispersible tabs
What is the dose of lamotrigine when given w/ valproate?
25mg on alternate days for 14 days
What is the dose of lamotrigine when given with enzyme inducers?
50mg OD for 14 days
What are the side effects of lamotrigine?
- Agitation, arthralgia, dry mouth, fatigue, sleep disorders, tremor
- Stevens-johnson syndrome + toxic epidermal necrolysis
- Hepatic disorders
- Blood disorders
- Disseminated intravascular coagulation
