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Flashcards in Chapter 1: Basic principles of prescribing Deck (7):
1

Enzyme inducers

 

 

increase P450 enzyme activity = reduced levels of other drugs

PC BRAS

  • Phenytoin
  • Carbamezapine
  • Barbituates
  • Rifampicin
  • Alcohol (chronic excess)
  • Sulphonylureas

+ smoking + griseofulvin

2

Enzyme inhibitors

= reduce P450 enzyme activity = increased levels of other drugs

AO DEVICES

  • Allopurinol
  • Omepraxole
  • Disulfiram
  • Erythromycin
  • Valproate
  • Isoniazid
  • Cirpofloxacin
  • Ethanol (acute intaxication) 
  • Sulphonamides 

+ metronidazole + cimetidine + amiodarone + imidazoles + SSRIs

3

Drugs that would be DETRIMENTAL intraoperatively if discontinued

Calcium Channel Blockers

Beta Blockers

 

Which therefore must be continued

4

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.

 

5

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

6

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
  • bupropion

Some medications such as benzodiazepines, baclofen and hydroxyzine may provoke seizures whilst they are being withdrawn.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).

7

Drugs metabolised by P450s!

Drugs Metabolised: COWEST

  • Ciclosporin
  • OCP
  • Warfarin
  • Epileptic: phenytoin, carbamazepine
  • Statins
  • Theophyline