Prescription Review Flashcards
Many prescriptions errors can be madee and this emphasises the need for a comprehensive prescribing routine that may be followed every time you prescribe. The following mneumonic (PReSCRIBER) covers all these pitfalls and related traps within the PSA.
What constitutes PReSCRIBER?
- Patient details (always check the name!)
- Reaction (ie. allergy plus the reaction)
- Sign the front of the chart
- check for Contraindications to each drug
- check Route for each drug
- prescribe Intravenous fluids if needed
- prescribe Blood clot prophylaxis if needed
- prescribe antiEmetic if needed
- prescribe pain Relief if needed
How do you ensure the correct patient details?
- New chart? → write name, DoB, hosp number
- Current chart? → check the name + DoB
How do you notice and record reactions?
- New chart? → complete allergy box incl any drug rxn mentioned by pt
- Current chart? → check allergy box
Do not forget that co-amoxiclav and Tazocin both contain penicillin
What should you remember to do with each prescription chart and even each individual prescription?
Sign the front of the chart / sign the prescription
Which drugs increase bleeding?
- Aspirin
- Heparin
- Warfarin
What are the contraindications to the drugs that increase bleeding?
- Avoid in pts who are bleeding, suspected bleeding or at risk of bleeding
- Prophylactic heparin is contraindicated in acute ischaemic stroke (risk of bleeding into the stroke)
- Enzyme inhibitors can increase warfarin’s effect (and thus increase INR or PT)
STEROIDS
What are the side-effects (and thus loosely, the contraindications) of steroids?
- Stomach ulcers
- Thin skin
- oEdema
- R + L heart failure
- Osteoporosis
- Infection (incl candida)
- Diabetes (commonly causes hyperglycaemia, uncommonly diabetes)
- cushing’s Syndrome
NSAID
What are the cautions and contraindications for NSAIDs?
- No urine (renal failure)
- Systolic dysfunction (HF)
- Asthma
- Indigestion
- Dyscrasia (clotting abnormality)
N.B. Aspirin is not CI in renal failure, heart failure or asthma
What 3 categories can we divide the side-effects of antihypertensives into?
- Hypotension (all)
-
Mechanistic
- bradycardia → beta-blockers, CCBs
- electrolyte disturbance → ACEi, diuretics
-
Specific
- ACEi → dry cough
- Beta-blockers → wheeze (in asthma), worsening acute HF (but helps chronic HF)
- CCB → peripheral oedema + flushing
- Diuretics → renal failure, gout (loops), gynaecomastia (K-sparing)
What should be remembered when checking the route for each drug?
- Vomiting → IM/IV/SC anti-emetics; also if short-term vomiting then not necessary to change route of other drugs too
- NBM → should still receive oral meds, incl prior to surgery
There is no single ‘right’ answer for most fluid prescriptions, but there are always ‘wrong’ answers.
In which two situations are IV fluids prescribed?
- Replacement fluids for dehydrated/acutely unwell pt
- Maintenance in pt who is NBM
In both instances, one must consider which fluid, how much to give and how fast
For replacement, which fluid should be given to all patients (as a rule of thumb)?
0.9% NaCl (crystalloid)
What are the exceptions to giving NaCl 0.9% for fluid replacement?
- Hypernatraemic or hypoglycaemic → 5% dextrose
- Ascites → human-albumin solution (HAS)
- Shocked from bleeding → blood transfusion
For replacement fluids, how much fluid should be given and how fast?
- Start by assessing BP, HR and urine output
- If tachycardic + hypotensive → 500mL bolus stat (or 250mL in HF)
- Reassess patient (HR, BP, UO)
Can predict how fluid-depleted an adult is by looking at obs
* Reduced urine output → 500mL of fluid depletion
* Reduced UO + tachycardia → 1L of fluid depletion
Reduced UO + tachy + shock → >2L fluid depletion
How much fluid should be prescribed as the maximum for a sick patient (replacement fluids)?
- Never more than 2L
- Effect on pt and thus rate of subsequent fluids should be reviewed regularly
For maintenance fluids, which fluids should be given and how much?
- Adults require 3L IV fluid / 24 hrs and elderly require 2L
- Adequate electrolytes by 1 salty + 2 sweet → 1L 0.9% NaCl and 2L 5% dextrose
For maintenance fluids, what is the potassium requirement?
- Use 5% dextrose or 0.9% NaCl containing KCl
- Guided by U+Es
- W/ normal potassium level, pts require roughly 40 mmol KCl per day, so put 20 mmol KCl in two bags
- IV potassium should not be given at more than 10 mmol/hour
How fast do we give maintenance fluids?
- 3L → 8 hrly bags (24/3)
- 2L → 12 hrly bags (24/2)
What is the blood clot prophylaxis for patients in hospital?
- Majority given prophylactic LMWH → dalteparin 5000 units daily SC + TEDS
- avoid warfarin/heparin if bleeding
- don’t give TEDS if peripheral arterial disease
Which antiemetic is prescribed for a nauseated patient?
- Regular antiemetic
- Cyclizine 50mg 8-hrly IM/IV/oral for most cases (SE: fluid retention)
- Metoclopramide 10mg 8-hrly IM/IV if heart failure
Cyclizine is a good first-line treatment for almost all cases except cardiac cases (as it can worsen fluid retention), whereas metoclopramide 10mg 8-hrly IM/IV is safer
Which antiemetic is prescribed for non-nauseated patients?
Same as nauseated but ‘as-required’ rather than regular
When should metoclopramide (dopamine antagonist) be avoided?
- Parkinson’s patients due to risk of exacerbating symptoms
- Young women due to risk of dyskinesia ie. unwanted movements especially acute dystonia → procyclidine will abort these dystonic attacks
What pain relief should be prescribed for patients?
- No more than 4g paracetamol per day
- NSAIDs can be introduced at any stage (if no CI)
- Morphine sulphate may be given orally → oramorph - the usual strength is 10mg/5mL
What is the painkiller treatment for neuropathic pain?
- Pain arising from nerve damage or disease → shooting / stabbing / burning
- 1st-line → amitriptyline 10mg oral nightly OR
- pregabalin 75mg oral 12-hrly
- Painful diabetic neuropathy → duloxetine 60mg oral daily
Which drugs are eliminated by the kidneys?
- CVS → atenolol / digoxin
- Neuro → opioids / gabapentin / lithium
- Infection → penicillins / aminoglycosides
- Other → LMWH / allopurinol / metformin
What are the nephrotoxic drugs (4)?
- NSAIDs
- Aminoglycosides
- Radiographic contrast material
- Trimethoprim
For sick-day rules, which drugs are to be withheld if there is a risk of volume depletion?
- ACEi
- ARBs
- Diuretics
- NSAIDs
- Metformin
Which drugs are hepatotoxic?
- Dose-dependent → paracetamol / methotrexate
- Idiosyncratic → phenytoin / co-amoxiclav
Which drugs can precipitate encephalopathy?
- Sedatives → opioiods / benzos / TCAs
- Hypokalaemic effects → diuretics
- Constipating effects → antimuscarinics
Which drugs are prescribed in micrograms, but often mistakenly substituted for miligrams?
- Digoxin
- Levothyroxine
- Tamsulosin
- Inhaled bronchodilators
Which drugs are prescribed in units?
- Insulin
- Heparins
Which drugs are prescribed weekly?
- Bisphosphonates
- Methotrexate
Don’t mistake for daily
Who are paracetamol dosing errors likely in?
- Children
- Adults receiving IV paracetamol who either have low body weight or existing liver disease
What are common drug interaction scenarios?
- Electrolyte abnormalities
- Renal impairment
- Postural hypotension/dizziness
- Arrhtyhmias (particular heart block, increased QTc)
- Over/under-anticoagulation
- Theophylline interactions
- Lithium interactions
What is the interaction between methotrexate and trimethoprim?
Both folate antagonists
What is the interaction between SSRIs and antiplatelets/NSAIDs?
Inhibit serotonin uptake in platelets (SSRIs) which creates theoretical risk of increasing bleeding especially with NSAIDs
What are the signs of serotonin syndrome?
- Confusion
- Agitation
- Hyperthermia
- Hyperrefflexia
- Clonus
- Hypertonia
What is the treatment for serotonin syndrome?
- Withdraw serotonergic drugs
- Cooling and supportive care
- Benzos as required
Which kinds of drugs precipitate hepatic encephalopathy?
- Drugs with sedative effects: sedating anti-histamines (e.g. chlorphenamine), benzodiazepines
- Drugs with potassium-lowering effects (because hypokalaemia increases renal ammonium production): thiazide diuretics, loop diuretics (e.g. furosemide)
- Drugs with constipating effects: opioids, calcium-channel blockers, etc
Some examples work by more than one of these mechanisms (e.g. opioids).
