Sunday, April 18, 2010

Pharmacology minutiae of antiepileptic drugs

from E Ramsey at AAN

1.  Enzyme induding drugs (Phenytoin, carbamazepine and lamotrigine) cause eighty percent or more reduction of many drugs including statins, (except one), so need to way increase dose of statin. Ditto for calcium channel blockers (think nimodipine after SAH),  antidepressants, erectile dysfunction drugs (all of them), and HAART therapy.

2.  Carbamazepine is related to weight gain almost as much as valproate

3.  Topiramate helps blood pressure and insulin sensitization needing readjustment of insulin

4.  Dilantin will not be absorbed with high pH such as pepcid or protonix

5.  LTG or TOP levels will increase two or three fold if you wean off an inducer like PTN due to decreased clearance

6.   Warfarin metabolism with Dilantin is variable, up or down, depending on genetics.

7.  Drugs that lower seizure threshold include theophylline, antihistamines, stimulants, antipsychotics, narcotics, hormones, antibiotics (PCN, metronidazole, lindane), antidepressants (SSRI, TCA's), baclofen, oral hypoglycemics, some immunosuppressants

8.  CBZ induces CYP34, and ethinyl estradiol is a substrate, hence lower bc pill levels.  

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