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Neuropathic pain Case 4

Patient presenting complaint:

‘I have this rotten toe and terrible pain in my lower legs’

Patient situation: history of presenting illness:

Sarah Martin is a 57-year-old woman who presents at the diabetic foot clinic with an infected great toe and increased lower leg pain associated with diabetic neuropathy. Following diagnosis of osteomyelitis of the great toe metatarsal surgery is undertaken; amputation of great toe + VAC dressing [negative pressure wound therapy] under general anaesthetic with local anaesthetic infiltration. Sarah is day 3 post-op.

Patient assessment

Past medical history: Type 2DM x18 years, HNT x 16 years, dyslipidaemia x12 years, morbid obesity

Social history: Sarah has been married for 32 years, has two adult children whom both live away from home. She works as a sales assistant in a department store. Denies tobacco use, drinks alcohol 1-2 glasses wine night

Family history: Father type 2 DM, HNT died age 72 from renal failure, mother dyslipidaemia, hypothyroidism & obesity alive and in fair health, one sibling an older brother type 2 DM & alcoholism

Medications: gabapentin 600mg po tds, metformin 1g po bd, lisinopril 20mg po od, fluoxetine 20mg po od, paracetamol 1g qid

Adverse drug reactions: Penicillin; hives

Pertinent information from review of symptoms, physical examination, lab results, x-ray & imaging:  Sarah reports increasing pain in both feet, characterised by very unpleasant tingling with numbness, severe shooting pains & dull moderate background ache. Sarah has been feeling progressively more tired and generally unwell, denies fevers. Examination of foot ulcer revealed malodourous wound with necrotic tissue and discharge & X-Ray changes consistent with osteomyelitis. Sarah is day 3 post amputation of great toe & metatarsal wedge with VAC dressing.

Medical image:

Diagnosis

NEUROPATHIC PAIN: DIABETIC NEUROPATHY

Post great toe amputation

Differential diagnoses

Neurotoxic medications, vitamin B12 deficiency, renal disease, chronic inflammatory demyelinating neuropathy, inherited neuropathy, vasculitis

Treatment Goals

? Infection and confirm, identify microbe/pathogen, analgesia to TREAT PAIN,

Pharmacotherapy

Analgesic (she is on gabapentin) family hx of renal failure,

?Antibiotic? (Not penecillin)

PEER TEACHING

Present causes of neuropathic pain

Hyperglycemia

CNS trauma

CNS diseases

PVD

Chronic alcohol use disorder

Present the treatment goals

Consult patient to determine shared goals

Stabilise patient and manage pain

Address the wound, potential infection and effectiveness of the dressing,

Educate the patient (disease course, diet/nutrition, alcohol’s affects on body and medications, family history and predisposition of illness, intended drug outcomes and drug action)

Assess and promote medication adherence

Monitor the patient ( i.e. use subjective pain scale, blood-glucose monitoring)

Present pharmacotherapy options

Gabapentin (indicated for neuropathic pain, monitor creatinine levels)

Insulin, metformin

Consider another anti-convulsant?

Antibiotics (if infection is present, not penicillin)

Present the drug information for gabapentin

Class/type: anticonvulsant

Indication: epilepsy, focal, diabetic neuropathy, pruritis (off label in end stage renal disease)

Drug action: binds to voltage gated Ca channels reducing calcium influx into pre-synaptic nerve terminals and possibly decreasing release of excitatory neurotransmitters aka decreases neuronal excitability

Side effects: dizziness, drowsiness, weight gain

Adverse effects: vomiting, diarrhea, mood changes ie depression and suicidality

Contraindications: Hypersensitivity to gabapentin, renal impairment, preexisting depression or suicidality

Nursing considerations: potential for abuse, monitor for sedation and respiratory depression, dependence or withdrawal therefore avoid abrupt halt, monitor for severe mood changes and increased suicidality, evaluate effectiveness regularly, monitor renal function, caution with pregnant or of childbearing age females due to potential fetal malformations and neonate withdrawal symptoms, teratogenicity in animal studies and no current advice surrounding breastfeeding, monitor infant drowsiness, weight gain and developmental milestones

Dosing regimen: oral only for neuropathic (300mg od day 1-2, 300mg tds starting day 3) or initially 300mg tds on day 1 and increase according to effect in increments of 300mg every 2/3 days up to 3,600 mg daily ***consider lower initial dose and slowly titrate

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Define acute pain in the context of acute pancreatitis

Sudden severe pain in the right upper abdomen that radiates to the back caused by inflammation of the pancreas over a short period of time

Epigastric pain

Fluid collection in the pancreas due to infection causing enlargement of the pancreas

Present the treatment goals

Relieve pain

Lifestyle changes and patient education regarding alcohol use – addressing the underlying cause

Management and monitoring of hypertension

Present pharmacotherapy options

Pain relief, Opioids – eg. Morphine

Antiemetics to reduce side effects of fentanyl

Antibiotics

IV fluids for hydration

Present the drug information for fentanyl

Class: Opioid

Binds to mu receptor

Inhibits pain signals

Iv onset fast

Lasts for 30-60 minutes

Good for short-term acute pain

Side effects: respiratory depression, sedation, constipation, nausea, bradycardia

Adverse effects: dependence: addictive

Patient education: can cause dizziness and sleepiness, can be dangerous with alcohol, addictive with prolonged use

Don’t drink alcohol with it

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Define acute on chronic pain in the context of back pain

Acute on chronic pain in the context of back pain for this is chronic back pain condition which has been flared-up by a work event strained his back which has caused sudden intense pain.

Present the treatment goals

-        Manage Mr B’s pain effectively by considering stronger short-term medication intervention.

-        Confirm spinal fusion is not worsening and not a contributing factor to his pain.

Present pharmacotherapy options

Continue NSAIDs: paracetamol, ibuprofen alongside a opioid for the acute pain (short-term). Codeine with some effect.

Could increase pain relief if not effective change to stronger opioid e.g. tramadol, morphine PO

You can use tricyclic anti-depressants at low dose good for neuropathic pain.

Present the drug information for codeine

Class & indications

Natural opioid (from morphine)

Indications: mild to moderate pain, cough suppression.

PD Molecular target

Opioid agonist

Binds to opioid (mOR) receptors and Is converted to morphine in the CNS via CYP2D6

PD physiological effect

Analgesia, sedation

Respiratory depression

Cough suppression

Reduced GI motility

Key pharmacokinetics

Absorption: good oral absorption

Metabolism: Hepatic (CYP2D6 converts it to morphine)

Elimination: Renal

Half-life: around 3 hours

Note: Genetic CYP2D6 variation affects efficacy/toxicity

Contraindications

Hypersensitivity to codeine/opioids, children under 12, severe respiratory depression, paralytic ileus, post-op children post tonsillectomy/adenoidectomy.

Cautions

Substance use history, hepatic/renal impairment, respiratory disease, CYPD26 variability.

Drug-drug interactions

CNS depressants: alcohol, benzodiazepines, other opioids = increase sedation. CYP2D6 inhibitor (decrease efficacy), Serotonergic drugs, Warfarin (monitor INR in long-term use).

Adverse effects (same across opioids)

Constipation, nausea, sedation, dizziness, dry mouth, respiratory depression, tolerance, dependence, itching

Monitoring

Monitor: RR, consciousness level, pain, bowel function, liver/renal function, signs of dependence or misuse.

Dosing regime

Pain (Adult): 15-60mg PO every 4-6 hours PRN (max: 240mg/day)

Cough: 10-20mg PO every 4-6 hours PRN

Often combined with paracetamol or NSAIDS

Important clinical practice considerations

Avoid in <12 years of age or post-op pediatric use

Educate on sedation risk

Consider laxatives

Monitor for signs of misuse

Naloxone for OD treatment

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Case Study Two - Back pain (acute Chronic Pain)

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Case Study Two - Back pain (acute Chronic Pain)

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Define acute on chronic pain in the context of back pain

When someone with chronic pain experiences an acute/worsening pain episode associated to a particular event.

Present the treatment goals

Reduce/Manage the acute pain caused by the work accident

Confirm spinal fusion has not been affected

Present pharmacotherapy options

Current Medications:

Paracetamol 1gm qid,

Ibuprofen 400 mg tds

Codeine Phosphate (recently added with some effect)

Consider stronger opioids if pain level doesn't decrease

Present the drug information for codeine

See image above