PSA Flashcards
Drugs which are enzyme inducers?
**Increase enzyme activity = decrease drug concentration.
Phenytoin Carbamazepine Barbituates Rifampicin Alcohol (chronic excess) Sulphonylureas
**PC BRAS
Drugs which are enzyme inhibitors?
**Decrease enzyme activity = increase drug concentration.
Allopurinol Omeprazole Disulfiram Erythromycin Valproate Isoniazid Ciprofloxacin Ethanol (acute intoxication) Sulphonamides
**AO DEVICES
Drugs to stop before surgery?
Insulin Lithium Anticoagulants/ antiplatelets COCP/ HRT K-sparing diuretics Oral hypoglycaemic Perindopril and other ACEi's
**I LACK OP
How long before surgery should you stop the COCP/ HRT?
4 weeks before surgery.
How long before surgery should you stop lithium?
The day before surgery.
How long before surgery should you stop potassium sparing diuretics/ ACEi’s?
The day of surgery.
What is an absolute contraindication to the prescription of gentamicin?
Myasthenia Gravis.
Gentamicin dose should be calculated according to what?
Ideal body weight.
How should you dose gentamicin if a patient weighs less than the stated ideal body weight?
Calculate the dose manually using 5-7mg/kg/day.
Most common prescribing regimen used for gentamicin?
Once daily dosing.
The dose interval of gentamicin on a once daily dosing regimen is determined by what?
The Hartford Nomogram.
How are doses of gentamicin normally rounded?
To the nearest 40mg (as gentamicin comes in 40mg ampoules).
Maximum dose of gentamicin?
560mg per day.
When should gentamicin levels be checked?
6-12 hours after the dose.
What should you do if a gentamicin level is not checked within the window?
Wait until blood levels are <1mg/L and then give the second dose.
**2nd dose cannot be given within 24 hours though.
When might the multiple daily dosing regimen for gentamicin be used?
For IE, neonatal sepsis or paediatrics.
What should be avoided in patients taking metronidazole?
Alcohol consumption
**Avoid during treatment and for 48 hours after metronidazole course completion.
If a patient with infection has a low BP, what should you withhold?
Anti-hypertensives.
How should metronidazole tablets be taken?
Should be swallowed whole during or after a meal with a glass of water.
How is warfarin monitored?
INR.
How is unfractionated heparin monitored?
APTT.
How are DOACs monitored?
No regular monitoring.
Reversal of warfarin?
Vitamin K ± PCC
Reversal of dabigatran?
Idarucizumab.
DOAC reversal?
None.
Anticoagulants to avoid if a patient has poor renal function?
Dabigatran + Rivaroxaban.
3 drugs that warfarin can interact with that are not enzyme inducers/ inhibitors?
COCP Theophylline Corticosteroids Tricyclics Pethidine Statins
When should warfarin be stopped prior to surgery?
Stop 3-5 days prior to surgery + check INR is <1.5 before surgery.
When should rivaroxaban + apixaban be stopped prior to surgery?
Stop 48 hours prior to surgery.
When should clopidogrel + ticagrelor be stopped prior to surgery?
Stop 5 days prior to surgery.
When should aspirin be stopped prior to surgery?
Continue it unless there is a high risk of bleeding associated with the surgery (neurosurgery/ prostatectomy).
Management of a patient taking warfarin with major bleeding?
Stop warfarin
Give urgent phytomenadione IV
Give urgent PCC (factors II, VII, IX + X)
**FPP can be used as an alternative if PCC not available
Preferred anticoagulants in patients with creatinine clearance of <15?
LMWH then UFH
OR
LMWH then warfarin
Anticoagulant preferred in patients who are haemodynamically unstable?
UFH
What are the normal daily fluid requirements for patients?
25-30ml/kg/day of water.
1mmol/kg/day of Na+, K+ and Cl-.
50-100g/day glucose.
How much glucose does 100ml 5% glucose contain?
5g (50g in 1L).
What is the Holliday-Segar formula?
100ml/kg/day for the first 10kg of weight.
50ml/kg/day for the next 10kg of weight.
20ml/kg/day for any weight over 20kg.