Prescribing Basic Principles

Question 1

What should all prescriptions be?

Answer 1

Legible
Unambiguous
Approved (generic) name, with some exceptions e.g. tacrolimus brands
IN CAPITALS
Without abbreviations (some exceptions again)
Signed
If a drug is PRN, provide 2 instructions - 1) indication and 2) a max frequency or total dose in 24h (e.g. BD or 1g)
If abx prescribed, include indication and stop/review date
Include duration if treatment is not long term or in GP setting.

Question 2

What does the PReSCRIBER mnemonic to help with a safe routine for prescribing stand for?

Answer 2

Patient details
Reaction (i.e. allergy + rxn)
Sign the front of the chart
check for Contraindications to each drug
check Route for each drug
prescribe IV fluids if needed
prescribe Blood clot prophylaxis if needed
prescribe antiEmetic if needed
prescribe pain Relief if needed

Question 3

Drugs to stop before surgery and when

Answer 3

I LACK OP:
Insulin
Lithium - day before
Anticoagulants / antiplatelets
COCP / HRT - 4 weeks before
K-sparing diuretics - day of surgery
Oral hypoglycaemics
Perindopril and other ACE-i - day of surgery

Question 4

Drugs to increase during surgery

Answer 4

Corticosteroids - as with sick day rules, at induction of anaesthesia, should be given IV steroids.
Patients on long-term corticosteroids may have suppression of the hypothalamic-pituitary-adrenal axis, therefore unable to mount an adequate physiological stress response to surgery - would result in profound hypotension

Question 5

General principle for stopping/continuing drugs in surgery?

Answer 5

General rule - most drugs continued, due to the risk of losing disease control outweighing the risk posed by drug continuation - with exceptions of certain drugs you should stop.
Stopping some drugs may be detrimental intraoperatively e.g. Ca channel blockers, beta blockers - these must be continued.

Question 6

Contraindications of anticoagulants / antiplatelets

Answer 6

Patients who are bleeding, suspected of bleeding or at risk of bleeding e.g. prolonged PT time due to liver disease
Prophylactic heparin contraindicated in acute ischaemic stroke due to risk of bleeding into stroke.

Question 7

Contraindications of steroids

Answer 7

Remembers by thinking of side effects
Stomach ulcers, Thin skin, Oedema, Right and left heart failure, Osteoporosis, Infection, Diabetes and Cushing’s syndrome.

Question 8

Contraindications and cautions of NSAIDs

Answer 8

No urine (renal failure), Systolic dysfunction (heart failure), Asthma, Indigestion, Dyscrasia (clotting abnormality)
(Whilst aspirin is technically an NSAID, it is not contraindicated in renal/heart failure, or asthma)

Question 9

Contraindications of antihypertensives

Answer 9

Consider side effects to remember contraindications
Hypotension (including postural)
Bradycardia - beta blockers or Ca channel blockers
Electrolyte disturbance - ACE -i and diuretics
Asthma / acute heart failure - beta blockers
Dry cough - ace-i
Peripheral oedema / flushing - ca channel blockers
Renal failure - diuretics
Gout - furosemide / bendroflumethiazide
Gynaecomastia - spirinolactone

Question 10

Considerations for route of drugs

Answer 10

If vomiting, give antiemetics non-orally.
If vomiting predicted to last a short time, changing route of other meds is usually not necessary (and can be difficult, especially in the case of drugs where doses of non-oral route is different, e.g. phenytoin)
Doses of common antiemetics are same regardless of route, e.g. cyclizine 50mg TDS, metoclopramide 10mg TDS.
A patient who is NBM should still receive their oral medication, whatever the indication for NBM.

Question 11

What two general indications are there for IV fluids?

Answer 11

Replacement fluids for a dehydrated / acutely unwell patient

Maintenance in a patient who is NBM / poor oral intake

Question 12

What are the three main considerations when prescribing fluids?

Answer 12

Which fluid, how much to give, and how fast to give it.

Question 13

Which fluid should be given?

1) Patient is hypernatraemic or hypoglycaemic
2) Patient has ascites
3) Shocked patient with systolic BP < 90 mmHg
4) Shocked from bleeding
5) All other patients!

Answer 13

1) 5% Dextrose
2) HAS (Human Albumin Solution) - albumin maintains oncotic pressure; furthermore, saline would worsen ascites due to high sodium content
3) Gelofusine (a colloid) - high osmotic content so stays intravascularly, thus maintaining BP for longer
4) Blood transfusion (colloid first if no blood available)
5) Normal Saline 0.9%, a crystalloid (or Hartmann’s depending on local guidelines)

Question 14

How do you decide how much fluid to give and how fast in replacement scenarios?

Answer 14

-Assess HR, BP and urine output
-If tachycardic or hypotensive: five 500mL bolus immediately (250ml if HF) then reassess
-If oliguric (and not due to obstruction), give 1L over 2-4h then reassess
As a general rule, should never prescribe over 2L of IV fluid for a sick patient - effect should be monitored regularly

Question 15

How fluid depleted are adult patients in these situations (replacement scenarios):

1) Reduced urine output (oliguric if <30ml/h, anuric if 0ml/h)
2) Reduced urine output plus tachycardia
3) Reduced urine output plus tachycardia plus shocked

Answer 15

1) 500ml of fluid depletion
2) 1L
3) 2L

Question 16

Maintenance fluids - How much IV fluid do adults require compared to the elderly?

Answer 16

Adults - 3L / 24 hours

Elderly - 2L / 24 hours

Question 17

What regimen of IV fluid provides adequate electrolytes over 24 hours in a maintenance regimen?

Answer 17

1L of 0.9% saline (or Hartmann’s) and 2L of 5% dextrose (1 salty and 2 sweet)

Question 18

How can potassium be provided in IV fluids / how much potassium does an adult / elderly require in a maintenance regimen?

Answer 18

Bags of 5% dextrose or 0.9% saline containing KCl can be used, but this is guided by U&Es.
Normal potassium - pts require roughly 40mmol KCl per day (so put 20mmol in two bags)
NB: IV potassium should not be given at more than 10mmol / hour

Question 19

How fast should maintenance fluids be given?

Answer 19

3L / day = 8-hrly bags

2L / day = 12-hrly bags

Question 20

What should you do every time you prescribe fluids?

Answer 20

Check U&Es to confirm what to give them
Check patient is euvolaemic / not fluid overloaded
Ensure patient’s bladder is not palpable if giving replacement fluids because of ‘reduced urine output’.

Question 21

Contraindication to compression stockings?

Answer 21

Peripheral arterial disease - risk of acute limb ischaemia

Question 22

What antiemetic prescription options are there for nauseated / not nauseated patients? Give two examples with doses.

Answer 22

Prescribe regular if nauseated, PRN if not.
-Cyclizine 50mg 8-hrly IM/IV/oral for most cases but causes fluid retention
-Metoclopramide 10mg 8-hrly IM/IV if heart failure
(If prescribing PRN, prescriptions would be ‘up to 8-hrly, or max TDS frequency)

Question 23

When should metoclopramide be avoided?

Answer 23

Dopamine antagonist
Avoid in Parkinson’s (exacerbates symptoms)
Young women due to risk of dyskinesia i.e. unwanted movements, especially acute dystonia. Also, rarely oculogyric crisis.

Question 24

Analgesia regular + PRN prescription if patient has:

1) No pain
2) Mild pain
3) Severe pain

Is there a role for NSAIDS?

Finally:

4) Neuropathic pain
5) Painful diabetic neuropathy

Answer 24

1) Regular - nil. PRN - paracetamol 1g PO up to QDS
2) Reg - Paracetamol 1g PO QDS. PRN - Codeine 30mg PO up to QDS (Tramadol could be used instead)
3) Reg - Co-codamol 30/500, 2 tablets PO QDS. PRN - Morphine 10mg PO up to QDS. (May also be given SC and IV, in order of effectiveness. Oramorph usually comes in two strengths, the more concentrated rarely used in hospitals - usually 10mg/5ml is used and should be specified).
An NSAID (e.g. ibuprofen 400mg PO TDS) may be introduced at any stage regularly or PRN if not contraindicated.

4) Amitriptyline 10mg PO ON / Pregabalin 75mg PO BD
5) Duloxetine 50mg PO OD

Question 25

Why do you need to be careful when prescribing paracetamol and other analgesics, e.g. co-codamol?

Answer 25

Need to check how much paracetamol pt is taking; may be on more than one preparation and thus over the daily max of 4g. e.g. pt taking 2 co-codamol 30/500 QDS plus PRN paracetamol is potentially taking too much.