PSA Generic Flashcards
Common Enzyme Inducers
(Mneumonic = PC BRAS)
Phenytoin
Carbamazepine
Barbiturates
Rifampicin
Alcohol (Chronic XS)
Sulphonylureas (e.g. Gliclazide, Glipizide)
Common Enzyme Inhibitors
(Mneumonic = AODEVICES)
Allopurinol
Omeprazole
Disulfiram
Erythromycin
Valporate
Isoniazid
Ciprofloxacin
Ethanol (Acute intoxication)
Sulphonamides
Consequence of an enzyme inducing drug
Increased enzyme activity –> Decreased drug concentration
Increased metabolism of drugs means reduced effect (pt may require increased concentration if taking an enzyme inducer to get desired effect)
Consequence of an enzyme inhibiting drug
Decreased enzyme activity –> increased drug concentration
Consequence of an enzyme inhibiting drug
Decreased enzyme activity –> increased drug concentration
e.g. patient in warfarin and taking erythromycin - need to be careful with dosing
Common drugs to stop before surgery
(Mneumonic = I LACK OP)
Insulin
Lithium
Anticoagulants / Antiplatelets
COCP/HRT
K-Sparing diuretics (e.g. Spironolactone)
Oral Hypoglycaemics
Perindopril and other ACE inhibitors
COCP and HRT: when to stop before surgery
4 weeks before surgery
Lithium: when to stop before surgery
Day before
Potassium sparing diuretics: when to stop before surgery
Day of surgery
(hyperkalaemia may develop if renal perfusion is impaired or if there is tissue damage)
ACE Inhibitors: when to stop before surgery
Day of surgery
(associated with severe hypotension after induction of anaesthesia)
Clopidogrel: when to stop before surgery
7 days
Oral hypoglycaemic drugs and insulin: when to stop before surgery
Metformin should be stopped (because it will cause lactic acidosis)
All other oral hypoglycaemics and insulin should be stopped as will cause hypos because NBM
Sliding scales should be started - dose dependent on capillary glucose measurements
long-acting insulin should be given day of surgery at a reduced dose (80%)
intravenous glucose 20 % should be given if blood-glucose drops below 6 mmol/litre, and blood-glucose checked every hour, to prevent a drop below 4 mmol/litre. If blood-glucose drops below 4 mmol/litre, intravenous glucose 20 % should be adjusted and blood-glucose checked every 15 minutes, until blood-glucose is above 6 mmol/litre
Warfarin: when to stop before surgery
5 days
INR must be <1.5
May have to reverse the warfarinisation with PO Vitamin K if the INR remains high on the evening before
DOACs: When to stop before surgery
Drugs that may exacerbate heart failure
- thiazolidinediones - pioglitazone is contraindicated as it causes fluid retention
- verapamil - negative inotropic effect
- NSAIDs/glucocorticoids - should be used with caution as they cause fluid retention
(low-dose aspirin is an exception - many patients will have coexistent cardiovascular disease and the benefits of taking aspirin easily outweigh the risks)
- class I antiarrhythmics - flecainide (negative inotropic and proarrhythmic effect)
How much fluid: just reduced urine output
500mL fluid depletion
How much fluid: reduced urine output and tachycardia
1L fluid depletion
How much fluid: reduced urine and tachy and shocked
> 2L fluid depletion
How much fluid does an adult require / 24 hours
3L for adults, 2L for elderly
Adequate electrolytes are provided by 1L 0.9% NaCl and 2L 5% dextrose
Adult potassium requirement in fluids
Normal potassium level:
- 40mmol KCl per day (so 20mmol KCl in 2 bags)
How fast to give maintenance fluids
3L per day - 8 hourly bags
2L per day - 12 hourly
Signs of fluid overload
Increased JVP
Peripheral / pulmonary oedema
Metaclopramide contraindications
Pt with Parkinson’s (it is a dopamine antagonist)
Young women and elderly - due to risk of dyskinesia
Inpatient VTE Prophylaxis
Prophylactic LMW heparin e.g. dalteparin 5000 units daily s/c
Compression stockings
Who should NOT be prescribed compression stockings
Patient with peripheral arterial disease (may cause limb ischaemia)
Domperidone vs metoclopramide - which one exacerbates parkinsonism
Bother dopamine antagonists
Metoclopramide crosses the BBB whereas domperidone doesnt - domperidone safe to use in parkinsons
Drugs that can cause hypokalaemia
Diuretics - loop diuretics, thiazide diuretics
Glucocorticoids, Mineralocorticoids
Drugs that can cause hyperkalaemia
ACE inhibitors - e.g. lisinopril
ARBs
K- sparing diuretics
Trimethoprim
Mannitol
Antimuscarinics examples
Oxybutynin (urinary freq./urgency)
Antimuscarinics side effects
CONFUSION in the elderly
PUPILLARY DILATION with LOSS OF ACCOMMODATION
DRY MOUTH
TACHYCARDIA (after transient bradycardia)
Drugs with anticholinergic effects
Cyclizine
Cyclizine in the elderly
Reduced dose recommended as has anticholinergic effects - can cause drowsiness and confusion
Anticholinergic side effects
Drugs that should be avoided when on methotrexate
- TRIMETHOPRIM (is also folate antagonist so high risk of bone marrow toxicity –> pancytopenia and neutropenic sepsis)
- NSAIDs (should be used with caution due to risk of nephrotoxicity)
N.B. methotrexate should be withheld during active infection
Medications that can exacerbate asthma
Beta-blockers
NSAIDs
(except aspirin as this rarely worsens asthma)
Clozapine worrying side effect
Agranulocytosis resulting in neutropenia
!! required immediate cessation of the drug
