increase P450 enzyme activity = reduced levels of other drugs
- Alcohol (chronic excess)
+ smoking + griseofulvin
= reduce P450 enzyme activity = increased levels of other drugs
- Ethanol (acute intaxication)
+ metronidazole + cimetidine + amiodarone + imidazoles + SSRIs
Drugs that would be DETRIMENTAL intraoperatively if discontinued
Calcium Channel Blockers
Which therefore must be continued
Drugs which must be INCREASED during surgery
Long-term corticosteroids e.g. prednisolone, as adrenal atrophy so can’t mount adequate physiological stress response to surgery. (As with doubling of steroids with sick-day rules) During induction of anaesthesia, patients should be given IV steroids.
Druggs to STOP before surgery
I LAACK OP
- Insulin: Variable, sliding scale
- Lithium: day before
- Anticoagulants (warfarin/heparin incl prophylactic dose): variable, occasionally continue
- Antiplatelets (aspirin, clopidogrel, dipyrifamole): variable, occasionally continue
- COCP/HRT: 4 weeks before
- K+-sparing diuretics: day of surgery
- Oral hypoglycaemics: patient NBM, metformin continue (unless risk of lactic acidosis e.g. contrast dyes)
- Perinodopril (and other ACEi): day of surgery
Drugs that worsen seizure control in patients with epilepsy:
The following drugs may worsen seizure control in patients with epilepsy:
- mefenamic acid
- methylphenidate (used in ADHD)
- alcohol, cocaine, amphetamines
- ciprofloxacin, levofloxacin
- aminophylline, theophylline
Some medications such as benzodiazepines, baclofen and hydroxyzine may provoke seizures whilst they are being withdrawn.
Other medications may worsen seizure control by interfering with the metabolism of anti-epileptic drugs (i.e. P450 inducers/inhibitors).
Drugs metabolised by P450s!
Drugs Metabolised: COWEST
- Epileptic: phenytoin, carbamazepine