Xanthine Derivatives

Question 1

Give 2 examples of xanthine derivatives

Answer 1

• Aminophylline

- Theophylline

Question 2

On what basis should xanthine derivatives be prescribed?

Answer 2

By brand

Question 3

What are the pharmacological effects of xanthine derivatives comparable to?

Answer 3

Caffeine and theobromine

Question 4

What are the pharmacological effects of xanthine derivatives?

Answer 4

• Allows bronchial smooth muscle relaxation

- Increases heart rate, contractility, and force of contraction

Question 5

What are the routes of delivery of xanthine derivatives?

Answer 5

PO and IV

Question 6

Why can xanthine derivatives not be given IM?

Answer 6

Too irritant

Question 7

If xanthine derivatives are to be given IV, how should this be done?

Answer 7

Very slow IV injection over at least 20 mins

Question 8

What are the indications for xanthine derivatives?

Answer 8

• Asthma

- COPD

Question 9

When should xanthine derivatives be used with caution?

Answer 9

• Elderly patients
• Heart failure
• Arrhythmias
• Other cardiovascular disease
• Liver damage
• Hyperthyroidism
• Hypokalaemia
• Viral infections

Question 10

Can xanthine derivatives be used when breastfeeding?

Answer 10

Should avoid breastfeeding for a couple of hours after taking aminophylline

Question 11

What monitoring should be done with xanthine derivatives?

Answer 11

• Monitor plasma theophylline concentration 4-6 hours after modified released
• Monitor plasma potassium in severe asthma

Question 12

What is the target plasma theophylline?

Answer 12

10-20mg/L

Question 13

Why should plasma theophylline be measured 4-6 hours after modified release administration of xanthine derivatives?

Answer 13

To establish if drug is within therapeutic range

Question 14

Why do you need to ensure xanthine derivatives are within the therapeutic range?

Answer 14

As they have a narrow therapeutic index

Question 15

Why should plasma potassium be monitored in severe asthma being treated with xanthine derivatives?

Answer 15

Risk of hypokalaemia with multiple medications (beta-2 agonists, steroids) taken for severe asthma

Question 16

What might interact with xanthine derivatives?

Answer 16

• Other xanthine derivatives
• Smoking
• Beta-2 agonists
• Diuretics
• Drugs that lower seizure threshold

Question 17

What can happen if aminophylline and theophylline are given together?

Answer 17

Patient can suffer from arrhythmias and convulsions

Question 18

What effect does smoking have on xanthine derivatives?

Answer 18

Reduces plasma concentration of drug

Question 19

What might happen if beta-2 agonists and xanthine derivatives are given together?

Answer 19

Increased risk of hypokalaemia

Question 20

What might happen if drugs that lower the seizure threshold are given with xanthine derivatives?

Answer 20

Increased risk of seizures

Question 21

Give an example of a drug that decreases the seizure threshold?

Answer 21

Quinolones

Question 22

Why can toxicity occur with xanthine derivatives?

Answer 22

Narrow therapeutic index

Question 23

What are the common side effects of xanthine derivatives?

Answer 23

• Nausea
• Vomiting
• Hypokalaemia
• Gastric irritation
• Tachycardia
• Palpitations
• Headache

Question 24

What are the rare side effects of xanthine derivatives?

Answer 24

• Pulmonary oedema
• Arrhythmias
• Myocardial ischaemia

Question 25

What counselling is required with xanthine derivatives?

Answer 25

• Toxicity

- Smoking habits

Question 26

What counselling is required regarding toxicity with xanthine derivatives?

Answer 26

Should warn patients about symptoms of toxicity - seizures, hypotension, arrhythmias

Question 27

What counselling is required regarding smoking with xanthine derivatives?

Answer 27

Remind patient to inform you if they start or stop smoking during treatment

Question 28

Why do patients need to tell you if they start or stop smoking during treatment with xanthine derivatives?

Answer 28

Dose adjustment may be required if a patient changes their smoking habits