A 24yo girl comes to the woman sexual clinic and seeks advice for contraception. She is on
sodium valproate.
a. She can’t use COCP
b. She can use COCP with extra precaution
c. She can use COCP if anticonvulsant is changed to carbamezapin.
d. She can use COCP with estrogen 50ug and progesterone higher dose
e. She can use COCP
answer: E
The danger with COCP is enzyme inducers which can lower the levels of the hormone in he blood, lithium is not an enzyme inducer! With Na Valproate, an inhibitor, levels will be increased, no precaution necessary as it is asking in terms of contraception
Inducers: decrease conc of drug in blood…RASAG
rifampicin
anticonvulsants, particularly phenytoin, carbamazepine, phenobarbitone and primidone
spironolactone, st johns wort
alcohol, long term
griseofulvin
Inhibiors: increase conc of drug in blood GO SIS CCCA
grapefruit juice
omeprazole
sodium valproate
isoniazid
sulphonamide
ciprofloxacin
cimetidine
clarithromycin/erythromycin
antifungals, amiodarone
Examples of drugs which interact with enzyme inhibitors/inducers
-
Warfarin -
COCP -
Theophylline -
Corticosteroids -
Tricyclics -
Pethidine -
Statins
Some other common interactions to know
Metformin & cimetidine (inhibits renal elimination)
Gentamycin & loop diuretics (renal failure risk)
ACE inhibitors & potassium-sparring diuretics (risk of hyperkalaemia)
ACE inhibitors & metformin (enhance hypoglycaemic effect)
Statin & macrolides
Statin & amiodarone (increased statin concentration and therefore risk of rhabdomyolysis)
Thiazide & PPI (hyponatraemia)
Thiazide & lithium (increase toxicity)