18. Prescribing in Pain Management

Peripheral Neuropathy

Refers to damage to the peripheral nerves outside the brain and spinal cord, often causing numbness, tingling, or pain in the hands and feet.

It is often caused by Diabetes OR a S/E of Metformin use as Metformin causes Vitamin B12 deficiency (cobolamin).

If a patient has low mood and peripheral neuropathy, what is the best choice of medication to treat both?

Duloxetine

A patient is prescribed morphine for acute pain. Which medicines should commonly be considered alongside it?

A. Antibiotic and steroid

B. Laxative, antiemetic and naloxone PRN

C. Anticoagulant and statin

D. PPI and insulin

E. Gabapentin and duloxetine in all cases

Recommended Anti-Emetic in Opioid-induced Nausea

Ondansetron (5-HT3 Antagonist) as it doesn't cause drowsiness.

A 48-year-old woman has widespread pain for 14 months. Investigations have not identified a clear structural cause. She sleeps poorly, feels invalidated by previous consultations, and has stopped exercising because she fears worsening the pain. She asks for pregabalin because “it works for nerve pain.”

What is the most appropriate initial approach?

A. Start pregabalin because her symptoms are long-term

B. Start regular co-codamol and review in 6 months

C. Complete a person-centred assessment, validate the pain, explore impact/goals, and discuss non-pharmacological options with possible antidepressant use if appropriate

D. Tell her the pain is psychological because scans are normal

E. Start oral NSAIDs regularly because chronic pain responds best to anti-inflammatory treatment

A 61-year-old man with chronic primary pain has been taking oxycodone MR for 9 months. Dose increases have not improved function, and he reports daytime sedation and constipation. He asks for a further dose increase because his pain score is still 7/10.

What is the most appropriate response?

A. Increase oxycodone because pain score remains high

B. Add pregabalin to reduce opioid requirement

C. Reassess benefit versus harm and discuss a shared plan to reduce/stop opioids gradually, including withdrawal issues

D. Stop oxycodone abruptly because NICE does not recommend it

E. Switch to transdermal fentanyl because patches are safer long term

Should Neuropathic Agents be offered for Sciatica?

No

- It is rarely serious, usually improving within 6-12 weeks through self-care, staying active, and gentle exercises.

A 57-year-old woman has sudden severe unilateral facial pain triggered by touching her cheek and brushing her teeth. Episodes are brief, electric shock-like and recurrent. Neurological examination is otherwise normal.

Which is the most appropriate initial pharmacological treatment?

A. Duloxetine

B. Carbamazepine

C. Morphine

D. Amitriptyline

E. Ibuprofen

Trigeminal Neuralgia

A chronic condition characterised by intense, sharp, stabbing, or electric shock-like sensations lasting from seconds to minutes, often triggered by light touch, eating, or talking.

A 66-year-old man with metastatic lung cancer develops new severe thoracic back pain. The pain wakes him at night and is worse on coughing. Later that day, he develops difficulty walking and urinary retention.

What is the most appropriate action?

A. Start co-codamol and review in 48 hours

B. Start gabapentin and arrange routine outpatient MRI

C. Immediately contact the MSCC coordinator and treat as an oncological emergency

D. Reassure him that back pain is common in cancer

E. Refer to physiotherapy without medical escalation

A patient with advanced cancer is taking oral sustained-release morphine twice daily. They have predictable breakthrough pain during transfers and can swallow tablets. They ask for a fast-acting fentanyl spray because they heard it works quickly.

According to NICE guidance, what is the most appropriate first-line rescue medicine?

A. Oral immediate-release morphine

B. Fast-acting fentanyl spray

C. Codeine

D. Diclofenac

E. Pregabalin

A 52-year-old patient with chronic primary pain has been taking oxycodone for months. They report no meaningful improvement in function despite dose increases and feel sedated. They ask for a further dose increase.

What is the most appropriate approach?

A. Increase the opioid dose because pain is still present

B. Switch immediately to fentanyl patch without discussion

C. Reassess pain, function and harms; discuss reducing opioids and using a broader care/support plan

D. Add diazepam for sleep

E. Add gabapentin because chronic primary pain always responds to gabapentinoids

A 61-year-old patient with known lung cancer develops severe progressive thoracic back pain. Over 24 hours he develops difficulty walking, leg weakness and urinary retention.

What is the most appropriate action?

A. Prescribe co-codamol and review in 1 week

B. Refer routinely to physiotherapy

C. Treat as suspected metastatic spinal cord compression and contact the MSCC pathway urgently

D. Reassure that back pain is common in cancer

E. Start gabapentin and discharge

A 72-year-old man with metastatic prostate cancer has persistent background pain and breakthrough pain several times daily. He can swallow tablets and has no significant renal or hepatic impairment. He is not currently on a strong opioid.

Which is the most appropriate initial strong opioid strategy?

A. Transdermal fentanyl patch first-line

B. Regular oral morphine with immediate-release morphine for breakthrough pain

C. PRN paracetamol only

D. Gabapentin alone

E. Intramuscular morphine when pain becomes severe

A 39-year-old warehouse worker has sciatica for 5 months. He has shooting pain down his leg and asks for pregabalin because his friend found it helpful. He has no red flags.

According to NICE guidance, what is the most appropriate response?

A. Start pregabalin and titrate upward weekly

B. Start oral corticosteroids

C. Explain that gabapentinoids are not recommended for sciatica and focus on self-management/exercise-based care

D. Start diazepam at night

E. Start long-term morphine

Morphine or Oxycodone in Renal Impairment?

Oxycodone

- Reduce dose (e.g., 50-75% of normal) and increase the dosing interval in severe renal impairment (eGFR < 30.

Codeine Age Requirements

> 12 Years Old

Not recommended for adolescents aged 12-18 years with breathing problems, e.g., asthma.

First-Line Strong Opioid for Advanced Progressive Disease when Oral Route is Suitable (NICE)

Oral morphine is first-line. NICE recommends oral sustained-release morphine for maintenance, with immediate-release oral morphine for breakthrough pain. Do not routinely start with patches if oral opioids are suitable.

Morphine Starting Dose in Advanced Progressive Disease with no Renal/Hepatic Impairment (NICE)

A typical starting total daily dose is 20–30 mg oral morphine per day, e.g. 10–15 mg modified-release morphine twice daily, plus 5 mg immediate-release morphine for rescue during titration.

First-line Rescue Treatment for Breakthrough Pain in a Patient on Maintenance Oral Morphine

Immediate-release oral morphine.

- NICE says do not offer fast-acting fentanyl as first-line rescue medication.

10mg Oral Morphine is Equivelent to....

100mg Dihydrocodeine = 100mg Codeine = 100mg Tramadol

How do you convert Oral Oxycodone to Oral Morphine Equivalent?

Approximate Rule = x 1.5/2 Oral Dose of Oxycodone.

Therefore...

Oral Oxycodone 10mg = Morphine 15/20mg

How do you convert Oral Morphine to Oral Oxycodone Equivalent?

Approximate Rule = Divide Oral Dose of Morphine by 1.5/2.

Therefore...

Oral Morphine 30mg = Oral Oxycodone 15-20mg

What should you do to the Calculated Equivalent Opioid Dose when Switching Opioids?

Usually reduce the calculated equianalgesic dose by 25–50% for safety, then titrate to response.

Use a larger reduction in frail/elderly patients, high doses, or intolerable side effects

Approximate Fentanyl Patch Conversion: 25 Micrograms/Hour Fentanyl Patch = ... Oral Morphine Dose

25 Mcg/Hour Fentanyl Patch ≈ 60 mg Oral Morphine per 24 hours.

Useful Exam Anchor...

- 12 Mcg/Hour ≈ 30 mg Oral Morphine/day.

- 25 Mcg/Hour≈ 60 mg Oral Morphine/day.

- 50 Mcg/Hour≈ 120 mg Oral Morphine/day.

How often is a Fentanyl Patch usually changed?

Every 72 hours/3 days.

- The dose should not normally be increased more frequently than every 72 hours.

What should you do if a Patient has Opioid Toxicity from a Fentanyl Patch?

Remove the patch, check for additional patches, seek urgent medical advice, and monitor closely.

- Fentanyl can continue entering the blood from skin stores after removal.

How long can Significant Opioid Effect continue after Removing a Patch?

After patch removal, residual drug in the skin can maintain significant blood levels for up to 24 hours, so monitor for ongoing toxicity.

Key Counselling Point when Applying a New Opioid Patch

Remove the old patch before applying the new one. Also record the date, time and site, and rotate sites.

- Failure to remove old patches can cause overdose.

How often are Buprenorphine Patches Changed?

7 Days

- Buprenorphine patches can be changed every 3, 4 or 7 days, depending on the brand/strength, but the commonly used lower-strength patches such as 5, 10, 15 and 20 micrograms/hour are usually 7-day patches.

Approximate Weekly Buprenorphine Patch Conversion to Oral Morphine

5 micrograms/hour ≈ 12 mg Oral Morphine/day

10 micrograms/hour ≈ 24 mg Oral Morphine/day

20 micrograms/hour ≈ 48 mg Oral Morphine/day

Approximate Higher-Dose Buprenorphine Patch Conversion

For buprenorphine patches changed every 3–4 days...

35 micrograms/hour ≈ 84 mg Oral Morphine/day

52 micrograms/hour ≈ 126 mg Oral Morphine/day

70 micrograms/hour ≈ 168 mg Oral Morphine/day

What does NICE say about Gabapentinoids and Opioids for Sciatica?

Do NOT offer gabapentinoids, other antiepileptics, oral corticosteroids or benzodiazepines for sciatica.

Do NOT offer opioids for chronic sciatica.

Why is Heat Dangerous with Fentanyl or Buprenorphine Patches?

Heat can increase drug absorption through the skin, increasing the risk of opioid toxicity.

Avoid hot water bottles, heat pads, saunas, hot baths and direct sunlight over the patch.

How should used Opioid Patches be disposed of Safely?

Fold the patch in half with the sticky sides together, wash hands, and keep away from children/pets because used patches can still contain active opioid.

According to NICE, should Transdermal Opioid patches be first-line if the patient CAN take Oral Opioids?

No.

- NICE says do not routinely offer transdermal patches first-line if oral opioids are suitable.

- Oral morphine is usually first-line for strong opioid treatment in advanced progressive disease.

1st Line Rescue Medicine for Breakthrough Pain in a Patient already on Regular Oral Morphine

Immediate-release Oral Morphine.

- NICE says not to use fast-acting fentanyl as first-line rescue treatment.

What is 5mg Oral Oxycodone approximately Equivalent to?

5 mg Oral Oxycodone ≈ 10 mg Oral Morphine

- So oral oxycodone is roughly twice as potent as oral morphine.

What does NICE say about Tramadol for Neuropathic Pain?

NICE says consider tramadol ONLY for acute rescue therapy.

- It should not be used as routine long-term neuropathic pain treatment in non-specialist settings.

When can Capsaicin Cream be considered in Neuropathic Pain?

For localised neuropathic pain when the patient wishes to avoid oral treatment or cannot tolerate oral options.

Opioid-Naïve

Opioid-naïve means the patient is not already tolerant to opioids because they are not taking regular opioids, or have not been taking them long enough/at high enough doses to develop tolerance.

So they are more sensitive to opioid effects, particularly, sedation, nausea/vomiting, constipation and respiratory depression.

Opioid-naïve = start low, titrate carefully, monitor sedation and respiratory rate.

Difference between Codeine and Dihydrocodeine

Codeine

- Converted to morphine by CYP2D6.

- Response varies a lot between patients.

- Poor metabolisers may get little pain relief.

- Ultra-rapid metabolisers may produce too much morphine and get toxicity.

- The MHRA notes that codeine is converted into morphine by CYP2D6, with ultra-rapid metabolisers converting faster.

Dihydrocodeine

- Very similar in structure to codeine.

- Acts as a mu-opioid agonist.

- Metabolised partly by CYP2D6 to dihydromorphine, but CYP2D6 phenotype appears to have less impact on clinical effect than with codeine.

Combination Products containing either Codeine or Dihydrocodeine

Codeine + Paracetamol = Co-Codamol OTC

Dihydrocodeine + Paracetamol = Co-Dydramol OTC low-dose products, e.g. Paramol-type products.

Warning: “Can cause addiction. For three days use only”

Packs greater than 32 tablets/capsules are not available as P Medicines.

They are Pharmacy-Only Medicines, not GSL. Therefore, they need pharmacist supervision.

When are Fentanyl Patches preferred and when are Buprenorphine Patches preferred?

Buprenorphine Patches preferred when...

- Lower opioid dose requirement

- Stable chronic pain

- Patient needs a patch but is not suitable for stronger patch options.

- A weekly patch would support adherence

- Cautious option in frailer patients, depending on local guidance.

Fentanyl Patches preferred when...

- Patient is already opioid-tolerant

- Pain is stable but requires a stronger opioid

- Oral route is unsuitable

- Patient has already tolerated opioids and needs a higher-dose transdermal option.

Important Safety Point:

Fentanyl patches should NOT be used in opioid-naïve patients, especially for non-cancer pain, because of the risk of serious respiratory depression. MHRA states that fentanyl patches are contraindicated in opioid-naïve patients in the UK for non-cancer pain.

Safest NSAID in a Patient with Cardiovascular Problems

Naproxen or Low Dose Ibuprofen

NSAID with Highest CVD Risk

MHRA states Diclofenac has highest cardiovascular risk than other non-selective NSAIDs and is similar to COX-2 inhibitors; naproxen and low-dose ibuprofen have the most favourable CV safety profiles.

Dose and Regimen of Breakthrough Pain

1/6th to 1/10th of the Total Daily Dose every 2-4 Hours PRN

What Patients might Oxycodone be More Suitable in and Why?

Patients who can't consume large amounts of morphine due to feeling nauseous.

Oxycodone is 1.5/2x more potent than morphine.

Dysmenorrhoea

Mefenamic Acid

Heavy Menstrual Bleeding

Tranexamic Acid