PRESCRIBING SKILLS PRACTICE QUESTIONS 3
Calculation
Case presentation
A 25-year-old woman is nil by mouth following an appendicectomy. She requires a single
dose of paracetamol for pain relief. She will not accept treatment in the form of suppositories
and a decision is made to use the IV route. The recommended IV dose of paracetamol is 15
mg/kg given over 15 minutes. She weighs 48 kg. Paracetamol intravenous infusion is
available in vials containing 10 mg/mL.
Calculation
What total volume of paracetamol intravenous infusion should she be given?
(Write your answer in the box below)
Answer: 72 mL
Answer box
Working
Dose required = 15 x 48 = 720 mg
Vials contain 10 mg/mL
Volume of infusion = 720/10 = 72 mL
Adverse drug reaction
Case presentation
A 65-year-old man with angina has started to take nifedipine m/r (Coracten XL®) 30 mg
orally daily to prevent attacks.
Question
Select the adverse effect that is most likely to be caused by this treatment.
(mark it with a tick)
ADVERSE EFFECT OPTIONS
A
ankle oedema
B
anorexia
C
heart failure
D
hyperglycaemia
E
urinary retention
Answer box
Option A Justification
Nifedipine causes vasodilatation that can result in ankle oedema.
Option B Justification
Nifedipine can cause anorexia but this is a rare adverse effect and much less likely to occur
than ankle oedema.
Option C Justification
Nifedipine has relatively little effect on the myocardium and rarely precipitates heart failure.
Option D Justification
Hyperglycaemia is a rare adverse effect of nifedipine, and less likely to occur than ankle
oedema.
Option E Justification
Nifedipine can occasionally cause polyuria/nocturia, but not urinary retention
Adverse drug reaction
Case presentation
A 47-year-old man presents to the out-of-hours GP service complaining of a widespread itchy
rash. He attended his GP 2 days ago complaining of a painful infected finger following an
injury. DH. Flucloxacillin 500 mg orally 6-hrly for 7 days and paracetamol 1g orally 6-hrly
as required.
The rash is thought to be drug-induced and he is advised to stop taking flucloxacillin.
Question
Select the most appropriate option for the management of this adverse drug event.
(mark it with a tick)
A
MANAGEMENT OPTIONS
adrenaline (epinephrine) 500 micrograms IM
B
calamine lotion to affected areas 8-hrly
C
chlorphenamine maleate 4 mg orally 6-hrly
D
complete a yellow card report
E
prednisolone 30 mg orally daily
Answer box
Option A Justification
This patient does not have any symptoms or signs of anaphylaxis and therefore adrenaline is
not indicated. Unnecessary use can be harmful.
Option B Justification
Calamine lotion is sometimes used to relieve itching but is often ineffective.
Option C Justification
An antihistamine may help to relieve the symptom of itch.
Option D Justification
This is a well-recognised adverse effect and therefore does not require reporting. Unusual
adverse effects and all adverse effects for new drugs (marked in BNF with a black triangle)
should be reported.
Option E Justification
Corticosteroids may be necessary in the management of chronic urticaria but are not
indicated as first-line treatment of a drug-induced rash that is likely to resolve with a few
days.
Prescription review
Case presentation
A 77-year-old man is referred to the medical assessment unit with abnormal liver function
tests. PMH. Angina, hypertension and osteoporosis. DH. His current regular medicines are
listed (right).
Investigations
Prothrombin time 13.2 s (11.5–15.5).
Serum albumin 38 g/L (37–49), bili 30 μmol/L (1–22), ALT 127 U/L (5–35), alk phos 130
U/L (45–105), serum gammaglutamyltranspeptidase 62 U/L (<50).
Question A
Select the ONE prescription that is most likely to be contributing to the abnormal liver
function.
(mark it with a tick in column A)
Question B
Select the ONE prescription that contains a serious dosing error.
(mark it with a tick in column B)
Resource associated with this item:
No resource has been associated with this item.
CURRENT PRESCRIPTIONS
Drug
Dose Route Freq.
alendronic acid 70 mg ORAL daily
aspirin
75 mg ORAL daily
atenolol
50 mg ORAL daily
calcium carbonate 1.25 g ORAL daily
lisinopril
20 mg ORAL daily
simvastatin
20 mg ORAL nightly
A B
Answer box
A Simvastatin can cause abnormal LFTs and should be avoided in liver impairment
B The dose should be 70 mg WEEKLY not daily
Data interpretation
Case presentation
A 56-year-old woman attends the anticoagulant clinic for review. PMH. Atrial fibrillation.
DH. Warfarin 5 mg orally daily.
Investigations
INR 6.5 (target 2.5).
There are no signs of bleeding.
Question
Select the most appropriate decision option with regard to the next dose of warfarin based
on these data.
(mark it with a tick)
DECISION OPTIONS
A
2 mg orally
B
3 mg orally
C
4 mg orally
D
5 mg orally
E
omit the next dose
Answer box
Option A Justification
This INR is high and reducing the dose of warfarin may not be sufficient to lower it in a
timely manner leaving the patient at risk of haemorrhage.
Option B Justification
This INR is high and reducing the dose of warfarin may not be sufficient to lower it in a
timely manner leaving the patient at risk of haemorrhage.
Option C Justification
This INR is high and reducing the dose of warfarin may not be sufficient to lower it in a
timely manner leaving the patient at risk of haemorrhage.
Option D Justification
This INR is high and leaving the dose of warfarin unchanged will allow this to continue
leaving the patient at risk of haemorrhage.
Option E Justification
With no sign of bleeding, BNF suggests withholding warfarin and reintroducing at a lower
dose after 1–2 days.
Therapeutic monitoring
Case presentation
A 46-year-old man is admitted with nausea and weight loss. After investigation, a
diagnosis of Addison’s disease is made. He is eventually discharged with a
prescription for hydrocortisone 20 mg orally each morning and 10 mg orally each
evening, and fludrocortisone 50 micrograms orally daily.
Question
Select the most appropriate monitoring option to assess the effectiveness of the
prescribed dose of corticosteroids over the next 3 weeks.
(mark it with a tick)
A
MONITORING OPTIONS
blood pressure lying and standing
B
body weight
C
plasma glucose
D
random serum cortisol
E
serum potassium
Answer box
Option A Justification
Postural hypotension is a symptom that is sensitive to inadequate corticosteroid;
if present, it should be treated with increase in dosage.
Option B Justification
This is important but is not a sensitive index of the need for corticosteroid.
Option C Justification
Plasma glucose may be affected by corticosteroid use, but is not an effective
method of monitoring response to treatment.
Option D Justification
Dosing of hydrocortisone to achieve appropriate peak concentration is helpful
initially but not for long-term monitoring.
Option E Justification
Serum potassium will rise if dosage is inadequate and fall if the dosage is too
high, but is a less valuable guide to the adequacy of corticosteroid dosage than
lying and standing blood pressure.
Communication
Case presentation
An 8-year-old girl is brought to the GP complaining of increased breathlessness. PMH.
Asthma for 4 years. DH. Salbutamol inhaler (100 micrograms/puff) two puffs via a spacer
device when required but has been requiring repeat prescriptions every 2 weeks for the last 2
months.
The GP prescribes a beclometasone inhaler (50 micrograms/puff) 2 puffs 12-hrly.
Question
Select the most appropriate information option that should be communicated to the mother.
(mark it with a tick)
A
INFORMATION OPTIONS
overuse of the beclometasone inhaler may cause mild tremor
B
the beclometasone inhaler may be used as required
C
the beclometasone inhaler should be used with a spacer device
D
the child should carry a steroid card
E
the child should stop using her salbutamol inhaler
Answer box
Option A Justification
overuse of an inhaled β2-agonist may lead to tremor, but this is not an adverse effect of
beclometasone.
Option B Justification
Inhaled corticosteroids must be used regularly for maximum effect.
Option C Justification
A spacer device should be used to minimise particle deposition in the mouth and maximise
delivery to the lung.
Option D Justification
It is not necessary to carry a steroid card when using standard doses of inhaled
corticosteroids.
Option E Justification
Beclometasone inhaler should be used regularly and salbutamol inhaler may still be used
when required for exacerbations of asthma.