Pain management

Question 1

What are some general principles of prescribing analgesia?

Answer 1

Regular analgesia is more effective than PRN.
Multimodal approaches are more effective and reduce the need for and thus the adverse effects of opioids.
To reduce side effects related to the dose of an opioid, use small doses at short intervals rather than lengthening the dose interval.

Question 2

Give an example of a mild painkiller on the WHO pain ladder.

Answer 2

Paracetamol

Ibuprofen/other NSAID

Question 3

Give examples of moderate painkillers.

Answer 3

Weak opioids e.g. codeine and tramadol

Question 4

Give examples of strong painkillers

Answer 4

Strong opioids e.g. morphine

Question 5

What are the pharmacokinetics of paracetamol?

Answer 5

Metabolised by the liver by a saturable mechanism so may be toxic in overdose. About 5% is renally excreted so dose may need to be adjusted in renal impairment.

Question 6

What is an important drug interaction with paracetamol?

Answer 6

Prolonged use of regular paracetamol could enhance the anticoagulant effect of warfarin.

Question 7

Under which conditions should you be wary of using NSAIDs?

Answer 7

Age >60
Patients at risk of GI mucosal damage (elderly, PUD, dyspepsia, steroids) - prescribe PPI
Hypovolaemia, hypotension, nephrotoxic medication e.g. ACEi and diuretics
Heart failure - NSAIDs can worsen or precipitate heart failure
NSAIDs may be associated with a small increased risk of thrombotic events, particularly if used in high doses and for long-term treatment.

Question 8

When should you avoid NSAIDs?

Answer 8

Bleeding history/ previous PUD
Aspirin sensitive asthma
Renal insufficiency including oliguria and heart failure
Hyperkalaemia
In pregnancy
In patients taking warfarn, aspirin and steroids

Question 9

How do opioids work?

Answer 9

Morphine is an agonist at mu receptors.

Question 10

What are the pharmacokinetics of opioids?

Answer 10

There is high first pass metabolism so the oral dose is about three times the parenteral dose. The dose may need reduction in liver disease.
The peak effect is at 60 minutes after oral administration and lasts about 4 hours.
There is also renal excretion of active metabolites so the dose must be reduced in renal failure.

Question 11

What are the side effects of opioids?

Answer 11

Sedation
Respiratory depression
Nausea and vomiting
Ileus and constipation
Pruritis
Hallucinations and dysphoria

Question 12

What are the contraindications to opioid use?

Answer 12

Acute respiratory depression
Conditions associated with raised intra-cranial pressure and in head injury, as they interfere with pupillary responses vital for neurological assessment

Question 13

Which drugs interact with opioids?

Answer 13

The most important interactions are with other sedating medications and alcohol.

Question 14

What drugs should be co-prescribed with morphine?

Answer 14

Laxative e.g. senna or lactulose.

Antiemetic - cyclizine first then prochlorperazine and ondansetron.

Question 15

What is important to specify when writing a prescription for PCA?

Answer 15

Drug name in full.
Background dose (must not be higher than the bolus dose)
Bolus dose
Lock out time

Question 16

How should you increase a PCA if a patient is in pain?

Answer 16

Ask two questions:

1) When you press the button does it take the pain away? If not, increase bolus dose.
2) Do you have pain when lying still? If yes, add or increase background dose.

Question 17

What drugs are usually put into epidural analgesia?

Answer 17

A mixture of a local anaesthetic and an opioid (in OUH bupivacaine and fentanyl are use)

Question 18

What are the main complications of epidurals?

Answer 18

Hypotension and motor block. it is important to rule out other cause of hypotension before attributing it to the epidural.

Question 19

When should naloxone be given to a patient on morphine?

Answer 19

If the patient is unarousable or the respiratory rate is <8/minute.

Question 20

What are the indications for codeine?

Answer 20

Mild/moderate pain, diarrhoea, cough

Question 21

When is oxycodone indicated?

Answer 21

It has a efficacy and side-effect profile similar to morphine and is approximately 1.5 times as potent. It is used primarily as a substitute for patients unable to tolerate morphine and is safer in patients with renal failure.

Question 22

How does tramadol exert its analgesic action?

Answer 22

An opioid effect and an enhancement of serotonergic and adrenergic pathways.