Basic principles of prescribing Flashcards
Basic principles of precribing
- Legible
- Unambiguous (e.g. not range of doses)
- Approved name e.g. salbutamol not ventolin
- CAPITALS
- Without abbreviations
- Signed
- PRN drugs: 1) Indication 2) Provide maximum frequency
- Abx: include the indication and stop/review date
Enzyme inducers (PC BRAS)
- Decrease drug concentrations
- Phenytoin
- Carbamazepine
- Barbiturates
- Rifampicin
- Alcohol (chronic excess)
- Sulphonylureas
Enzyme inhibitors (AO DEVICES)
- Increases drug concentrations
- Allopurinol
- Omeprazole
- Disulfiram
- Erythromycin
- Valproate
- Isoniazid
- Ciprofloxacin
- Ethanol (acute intoxication)
- Sulphonamides
Drugs to increase during surgery
- Pts on LT corticosteroids (e.g. prednisolone) commonly have adrenal atrophy = unable to mount an adequate physiological response to surgery (if steroids are discontinued they risk profound hypotension)
- ‘Sick day rules’ = pts on steroids double their daily dose to counter increased steroid requirement)
Drugs to stop before surgery
I LACK OP I - Insulin L = Lithium A - Anticoagulants/antiplatelts C - COCP/HRT K - K-sparing diuretics O - Oral hypoglycaemics P - Perindopril (+ other ACEIs)
When to stop COCP and HRT?
4 weeks before surgery?
When to stop lithium?
Day before
When to stop K+ sparing diuretics/ACEIs?
Day of surgery
When to stop anticoagulants/ oral hypoglycaemic drugs and insulins?
Variable
- Pts are NBM before surgery = metformin should be stopped because it will cause LACTIC ACIDOSIS
- The other hypoglycaemics and insulin will cause hypoglycaemia if not stopped
(SLIDING SCALE)
Safe routine for prescribing
- Ensuring correct patient prescription/drug chart
- Noticing + recording allergies
- Signing front of drug chart
- Consider contraindications for each drug prescribed
- Consider route for each drug prescribed
- Consider need for IV fluids/thromboprophylaxis/antiemetics/pain releif
PReSCRIBER
- Patient details
- REaction (i.e. allergy + reaction_
- Sign front of chart
- Contraindications of drugs?
- Route of each drug?
- IV fluids if needed
- Blood clot prophylaxis needed?
- antiEmetic needed?
- pain Relief needed?
Drugs that increase bleeding
- Aspirin
- Heparin
- Warfarin
Shouldn’t be given to pts who are actively bleeding, at risk of bleeding or suspected bleeding
Prophylactic enoxaparin
Contraindicated in acute ischaemic stroke = risk of bleeding into stroke
Erythromycin + warfarin
Erythromycin = enzyme inhibitor therefore decreases metabolism of warfarin + increases warfarin levels = increase INR
Steroid effects (STEROIDS)
- S: stomach ulcers
- T: thin skin
- E: oEdema
- R: R + L heart failure
- O: osteoporosis
- I: infection (including candida)
- D: DM
- S: cushing’s Syndrome
NSAID cautions/contraindications (NSAID)
- N: No urine (renal failure)
- S: Systolic dysfunction (heart failure)
- A: Asthma
- I: Indigestion (peptic ulcer)
- D: Dyscrasia (clotting abnormality)
Whilst aspirin is an NSAID = not contraindicated in renal failure or heart failure, and can be used in asthmatics (w/ caution)
Antihypertensives - effects
1) Hypotension (including postural hypotension) may result from all groups
2) Bradycardia - BB and some CCB
3) Electrolyte disturbances - ACEI and diuretics
ACEI
Dry cough
Beta blockers
- Wheeze in asthmatics
- Worsening of acute heart failure but helpful in chronic heart failure
CCB
- Peripheral oedema + flushing
Diuretics
- Can cause renal failure
- Loop diuretics e.g. Furosemide can cause gout and K+- sparing diuretics (spironlactone) can cause gynaecomastia
Antiemetic choice - nauseated
- Regular anti-emetic:
Cyclizine 50mg 8 hourly IM/IV/oral for most cases but fluid retention
Metoclopramide 10mg 8 hourly IM/IV if heart failure
Antiemetic choice - not nauseated
- PRN anti-emetic:
Cyclizine 50mg 8 hourly IM/IV/oral for most cases but fluid retention
Metoclopramide 10mg 8 hourly IM/IV if heart failure
Antiemetic - common exam traps
Avoid metoclopramide (dopamine antagonist) for:
- Pts w/ PD = exacerbation of symptoms
- Young women = risk of dyskinesia (unwanted movements - especially acute dystonia)
Paracetamol - common trap
- Daily maximum of 4g
- Check they aren’t on multiple drugs containing paracetamol +- PRN paracetamol
- Common e.g. is paracetamol + co-codamol = calculate how many g patient is being prescribed and omit if too high
Analgesia - choices
- No pain: PRN paracetamol 1g up to 6 hourly oral
- Mild pain: regular paracetamol 1g 6 hourly oral and PRN codeine 30mg up to 6 hourly oral
- Severe pain: co-codamol 30/500 2x tablets 6 hourly oral w/ PRN morphine sulphate 10mg up to 6 hourly oral
