High risk drugs

Question 1

What is the target plasma concentration of phenytoin?

Answer 1

10-20mg/L
(or 40-80micromol/L)

Question 2

What are the signs of toxicity with phenytoin overdose?

Answer 2

Nystagmus, dipoplia, slurred speech, confusion, hyperglycaemia

Question 3

What are cautions associated with phenytoin?

Answer 3

Enteral feeds - interrupt feed for 2 hours before and after dose.

HLA allele - presence of allele can increase risk of SJS

Question 4

Which side-effect is a sign to discontinue phenytoin?

Answer 4

A rash developing. Reintroduce phenytoin cautiously if rash was mild (Measles-like), but discontinue immediately if there is reccurent rash.

Question 5

What are the signs and symptoms of SJS?

Answer 5

headache, joint pain and cough can precede the rash.

rash looks like a target - dark/purple centre, surrounded by lighter area

blistering and peeling skin

(FYI: SJS is also commonly called toxic epidermal necrolysis)

Question 6

What is the target plasma concentration of carbamazepine?

Answer 6

4-12mg/L measured after 1-2 weeks

Question 7

What symptoms should patients be advised to look out for when on carbamazepine?

Answer 7

fever, rash, mouth ulcers, bruising, or bleeding develop - seek immediate medical attention

Question 8

Blurred, yellow vision is a sign of toxicity with which drug?

Answer 8

Digoxin

Question 9

What is the target plasma concentrations of theophylline and when do you measure it?

Answer 9

10-20mg/L - achieves satisfactory bronchodilation.

Measure 5 days after starting oral treatment, and at least 3 days after dose adjustments.

Collect blood sample 4-6 hours after oral dose of MR tablets (only form available)

Question 10

What signs and symptoms occur in theophylline toxicity?

Answer 10

Vomiting (severe and intractable), dilated pupils, sinus tachycardia, hyperglycaemia.

Convulsions, arrythmias (severe hypokalaemia) and haematemesis - in severe overdoses

Question 11

What sorts of thing decrease plasma-theophylline concentrations?

Answer 11

Smoking
Alcohol consuption

Question 12

How do you perform TDM for lithium?
What are the general target levels?

Answer 12

plasma-conc should be measured 12 hours post-dose.

Target = 0.4-1mmol/L (lower end of the range should be achieved for maintenance and elderly)

Question 13

What is the higher target of lithium that is sometimes required? When should it be used?

Answer 13

target 0.8–1 mmol/litre - for patients who have relapsed or have acute episodes of mania
[SPC states 0.8-1.2mmol/L; should never exceed 1.5mmol/L]

Question 14

Which chemotherapy drugs are most associated with oral mucositis?

Answer 14

Methotrexate
Fuorouracil
Anthracyclines

Question 15

Which cytotoxics are NOT associated with bone marrow suppression?

Answer 15

Vincristine
Bleomycin

Question 16

Which chemotherapy agents are highly emetogenic ? (name 3 drugs)

Answer 16

cisplatin
dacarbazine
cyclophosphamide

Question 17

Which 3 medications are used for prevention of acute N&V in patients at high risk of emesis?

Answer 17

dexamethasone + aprepitant + 5HT3-receptor antagonist (ondansetron)

Question 18

Name examples of anthracyclines?

Answer 18

daunorubicin
doxorubicin
epirubicin
idarubicin

Question 19

Which cytotoxics are most associated with cardiotoxic effects?

Answer 19

Anthracyclines - dose-related, cumulative, and potentially life-threatening cardiotoxic side-effects

Question 20

What colour do the anthracyclines (e.g. doxorubicin, idarubicin) change urine to?

Answer 20

Pink or red for upto 48 hours after treatment

Question 21

What are key interactions of methotrexate?

Answer 21

All PPIs - decrease clearance of mtx

Trimethoprim - increase risk of haematological s/e

Penicillin antibiotics - increase the risk of toxicity

Live vaccines - increased risk of infections

Question 22

Which medications can affect the release of mesalazine GR or MR tablets?

Answer 22

medications which lower the stool pH e.g. lactulose

This prevents the release of mesalazine

Question 23

Which electrolyte imbalances increases the risk of digoxin toxicity?

Answer 23

hypokalaemia
hypomagneseamia
hypercalcaemia

Question 24

What are target serum digoxin levels?

Answer 24

0.7-2nanograms/mL

Question 25

What levels indicate high chance of digoxin toxicity if patient also presents with symptoms?

Which levels indicate definite toxicity?

Answer 25

1.5-3ng/ml - high likelihood of toxicity

great than 3ng/ml - definite toxicity

Question 26

Advice for methotrexate missed doses?

Answer 26

1-2 days since missed dose - take ASAP

more than 3 days since missed dose - skip dose

Question 27

What are the baseline monitoring requirments for amiodarone?

Which tests need to repeated and how frequently?

Answer 27

Chest X-ray (prior to starting)
LFTs and TFTs (prior and 6 monthly)
Electrolytes (especially potassium prior to starting)
eye tests

Question 28

What adjustments may need to be made to warfarin during COVID infection?

Answer 28

Reduced doses (monitor INR)

Acute illness can exaggerate effects of warfarin.

Question 29

What side-effects can amiodarone cause (list 4)

Answer 29

Corneal microdeposits

Impaired thyroid function

Hepatotoxicity

Pulmonary toxicity