Immediate management

1. Grade and document neuropathy: pain score, ankle reflexes, gait/transfers, strength, sensory level, constipation/urinary retention, cranial neuropathy.
2. Discuss withholding or reducing the next vincristine dose with the treating ALL team, following the exact COG protocol. Functional motor impairment is clinically significant toxicity. Vincristine causes a dose-related length-dependent sensorimotor neuropathy and may cause autonomic bladder/bowel dysfunction. Bradley and Daroff's Neurology in Clinical Practice, p. 2710; Adams and Victor's Principles of Neurology, p. 1227.
3. Review and avoid interacting medicines that raise vincristine exposure, especially azole antifungals such as voriconazole, posaconazole, itraconazole, and strong CYP3A inhibitors where alternatives are possible.

Neuropathic pain treatment

• Gabapentin is commonly used first in pediatric practice: start low, often as a bedtime dose, then titrate gradually over several days based on pain relief, daytime sedation, dizziness, renal function, and weight. It helps burning, tingling, allodynia, and sleep disruption.
• Pregabalin is an alternative if gabapentin is ineffective or poorly tolerated.
• Duloxetine has the best evidence for established painful chemotherapy-induced peripheral neuropathy in adults, but pediatric evidence and use are less certain. It should be considered only with pediatric oncology/pain input, particularly if there are mood symptoms, nausea, interaction concerns, or inability to use gabapentinoids. The ASCO CIPN guideline supports duloxetine for painful CIPN in adults and emphasizes dose delay/reduction or stopping neurotoxic chemotherapy when neuropathy causes functional impairment.
• Paracetamol/acetaminophen can be used for superimposed nociceptive or musculoskeletal pain, if liver function and total daily dosing permit. It is usually inadequate alone for neuropathic pain.
• If pain is severe despite the above, use short-term opioid rescue only under the oncology/palliative-pain service, with a bowel regimen and close sedation monitoring. Opioids will not improve the neuropathy itself.

Supportive measures

• Physiotherapy and occupational therapy now: strengthening, transfer training, ankle-foot orthoses if needed, wheelchair safety, fall prevention, and hand-function work.
• Assess/treat constipation, hydration, urinary retention, and orthostatic symptoms, since vincristine can cause autonomic neuropathy.
• Check potentially contributory/reversible factors: glucose, B12/folate, electrolytes including magnesium, thyroid function if clinically indicated, and medication list.
• Neurology review with nerve-conduction studies/EMG can help characterize severity, but should not delay urgent imaging if a central cause is possible.

• New or progressive bilateral leg weakness, particularly loss of walking ability or rapid decline. This patient is wheelchair-dependent with bilateral lower-limb weakness, which is concerning.
• New bladder or bowel dysfunction, especially:
  • urinary retention or overflow incontinence
  • new urinary or fecal incontinence
  • reduced awareness of bladder filling
  • constipation with neurologic change
    This patient has urinary urgency. Urgency alone is less specific than retention/incontinence, but with bilateral weakness it warrants urgent assessment.
• Gait disturbance or inability to stand/transfer.
• A sensory level on the trunk or a clear change in sensation below a particular spinal level, rather than only distal stocking sensory loss.
• Saddle anesthesia: numbness of the perineum, genitals, buttocks, or inner thighs. This is particularly suggestive of conus/cauda equina involvement.
• New severe spinal pain, focal vertebral tenderness, radicular/shooting pain down one or both legs, night pain, or pain worsened by cough, sneeze, straining, or lying flat.
• Upper motor neuron signs below a cord lesion: hyperreflexia, clonus, extensor plantar responses, spastic tone. Acute compression may initially cause reduced reflexes, so absent reflexes do not fully exclude it.
• Reduced anal tone, reduced perianal sensation, sexual dysfunction, or rapidly progressive neurologic deficit.
• In an immunocompromised child, fever/back pain or severe localized tenderness also raises concern for epidural abscess, while thrombocytopenia or anticoagulation raises concern for epidural hematoma.

Immediate actions

1. Admit and escalate immediately
   • Pediatric oncology/hematology
   • Pediatric neurology
   • Neurosurgery/spinal surgery
   • Radiation oncology
   • Pediatric anesthesia/PICU if there is rapid progression
2. Urgent MRI of the whole spine with contrast
   • Do not image only the painful area, because lesions can be multifocal.
   • If MRI is unavailable or contraindicated, discuss CT myelography.
   • Serial neurologic observations: power, tone, reflexes, sensory level, gait/transfers, perianal sensation/anal tone when appropriate, and bladder function.
3. Protect the spine and manage complications
   • Flat/log-roll handling and spinal precautions if instability is possible, until reviewed by the spine team.
   • Strong analgesia as needed.
   • Bladder scan and catheterization if retention or high post-void residual is present.
   • Bowel regimen, pressure-area care, DVT prevention as appropriate, and early physiotherapy/rehabilitation.

Steroids

Definitive treatment depends on MRI cause

In this patient

Management plan

1. Modify the offending chemotherapy promptly

• Grade and document toxicity before each dose: pain, walking/transfers, ankle reflexes, distal power, sensory loss, constipation, urinary symptoms, and cranial nerve signs.
• Given this patient's wheelchair-level weakness, discuss holding the next vincristine dose urgently with the treating pediatric ALL team.
• Restart, reduce, omit, or adjust later doses only according to the COG 0434 protocol and local pediatric oncology decision-making. Do not substitute or permanently discontinue vincristine independently, because it is an important ALL drug.
• Exclude and stop avoidable potentiators. In particular, review antifungals and avoid strong CYP3A inhibitors when possible, especially itraconazole, voriconazole, and posaconazole, which can markedly worsen vincristine neurotoxicity.

2. Treat neuropathic pain

• Gabapentin is a reasonable first practical option for painful paresthesia/allodynia and sleep disruption. Start low and titrate gradually based on weight, renal function, sedation, dizziness, and response.
• Pregabalin is an alternative if gabapentin is ineffective or poorly tolerated.
• Duloxetine is the drug with the best adult evidence for established painful chemotherapy-induced peripheral neuropathy. It may be considered with pediatric pain/oncology supervision, but evidence in children with vincristine neuropathy is limited. Adult guideline recommendations should not be directly converted into pediatric prescribing.
• Use paracetamol/acetaminophen for additional musculoskeletal pain if appropriate, but it is not sufficient as monotherapy for neuropathic pain.
• If pain is uncontrolled, use a short-term opioid rescue plan only under oncology/palliative-pain supervision, with sedation monitoring and a bowel regimen.

3. Address motor disability and prevent injury

• Urgent physiotherapy and occupational therapy: transfer training, graded strengthening, range-of-motion exercises, gait reassessment, wheelchair safety, and energy conservation.
• Consider ankle-foot orthoses for foot drop or ankle weakness.
• Institute fall prevention and home/ward safety measures.
• Assess for pressure injuries if wheelchair-bound, and provide appropriate seating and skin care.
• Serial neurological examinations. Consider nerve-conduction studies/EMG if the diagnosis is uncertain, weakness is disproportionate, or there is inadequate recovery after vincristine modification.

4. Manage autonomic symptoms

• Ask specifically about constipation, abdominal distension, vomiting, urinary retention, incomplete emptying, and postural dizziness.
• Perform a post-void residual bladder scan. Urinary urgency can occur for many reasons; retention or a high residual requires prompt management.
• Treat constipation proactively with an oncology-approved bowel regimen, because vincristine can cause severe autonomic gut dysfunction, including ileus.
• Catheterize if retention is confirmed and obtain urology/neurology input if persistent.

5. Exclude contributors and alternate diagnoses

• Medication interaction review, especially azoles and other CYP3A inhibitors
• Electrolytes, renal and hepatic function, glucose
• Vitamin B12/folate if risk factors exist
• Infection, nutritional compromise, steroid myopathy, and leukemia-related neurologic disease if atypical

Practical disposition for this case

• Sedation and respiratory depression
• Nausea and constipation, which can worsen vincristine-related autonomic bowel dysfunction
• Urinary retention
• Seizures
• Serotonin toxicity if combined with serotonergic drugs, especially duloxetine, amitriptyline/nortriptyline, SSRIs, or linezolid

• limited to rescue use while a neuropathic agent is being started/titrated
• reviewed daily for benefit, sedation, respiratory rate, bowel function, and bladder emptying
• accompanied by a bowel regimen if an opioid is used

Neurobion cream on the foot

• it may irritate the skin or cause contact dermatitis
• it should not replace systemic neuropathic-pain treatment
• avoid vigorous rubbing or massage because touch itself is painful
• do not apply to broken, infected, irradiated, or severely fragile skin

Practical approach

1. Treat the cause: urgently review/withhold or modify vincristine according to the ALL protocol.
2. Start a neuropathic agent, usually gabapentin first in pediatric practice, with gradual titration and monitoring.
3. Consider topical lidocaine for focal touch-evoked foot pain after clinician review.
4. Reserve tramadol only for short-term uncontrolled breakthrough pain under oncology/pain-team supervision.
5. Manage constipation proactively and check a post-void residual, given the urinary symptoms.

• 30 mg orally once daily for 1 week
• Then, if tolerated, 60 mg orally once daily

• 30 mg once daily initially, preferably after food
• Review nausea, dizziness, sleep change, mood/behavior, BP, and pain response after 1-2 weeks
• Increase to 60 mg once daily only if needed and tolerated

• Do not combine duloxetine with tramadol routinely. Both increase serotonin activity, creating a risk of serotonin toxicity, and both may contribute to nausea, dizziness, and falls.
• Avoid or use specialist input with significant hepatic disease, severe renal impairment, uncontrolled hypertension, seizure risk, or concurrent serotonergic medicines such as SSRIs, SNRIs, TCAs, linezolid, or MAO inhibitors.
• Monitor closely for suicidal thoughts or major behavioral change in children/adolescents after starting an antidepressant.
• Duloxetine may ease pain but will not reverse the motor neuropathy. Vincristine modification, rehabilitation, bowel/bladder assessment, and repeated neurologic examination remain the priority.

• The pain is neuropathic allodynia, for which gabapentin/pregabalin, and sometimes duloxetine, target the mechanism better.
• The patch has a slow onset and long duration, making it difficult to titrate if the pain, sedation, bowel function, or neurologic status changes.
• The patient has possible vincristine autonomic neuropathy. Opioids can worsen constipation, ileus, urinary retention, dizziness, and falls.
• If the patient is a child or under 18, many transdermal buprenorphine products have no established pediatric safety/efficacy. The exact product label and local pediatric oncology policy must be checked.
• It is unsuitable for breakthrough pain. A short-acting, supervised rescue analgesic is needed if opioid analgesia is required.

When it might be reasonable

1. Compression and other neurologic emergencies have been excluded.
2. Pain is severe, persistent, and stable despite optimized neuropathic treatment.
3. The child has an ongoing opioid requirement, not just intermittent pain.
4. Constipation and bladder emptying are actively monitored and manageable.
5. Caregivers can safely store, apply, and dispose of the patch.
6. A plan exists for breakthrough pain and for monitoring respiratory rate and sedation.

Important safety points

• Do not use it with tramadol routinely. This creates additive opioid adverse effects without a good reason.
• Combining a patch with gabapentin or pregabalin can increase sedation and respiratory-depression risk, so start one medication at a time and monitor closely. The buprenorphine patch label specifically warns about additive risk with CNS depressants, including gabapentinoids.
• Do not apply external heat over or near the patch, and avoid fever-related overheating, as this may increase opioid absorption.
• Avoid if there is respiratory compromise, suspected paralytic ileus, or significant uncontrolled sedation. The product safety information warns of potentially life-threatening respiratory depression.

Preferred sequence here

1. Review/withhold vincristine according to protocol.
2. Start and titrate gabapentin or use pregabalin if appropriate.
3. For localized foot allodynia, consider clinician-approved topical lidocaine on intact skin.
4. If pain remains severe, use an opioid under inpatient pediatric oncology/pain-team supervision.
5. Consider a buprenorphine patch only if pain becomes stable and continuously opioid-requiring, not as the initial response to acute touch-evoked neuropathic pain.

Review of the prescribed regimen

1. Pregabalin 75 mg twice daily

• renal function is normal
• the patient is monitored for sedation, dizziness, confusion, and worsening gait/transfer safety
• it is titrated only after assessing benefit and adverse effects

2. Duloxetine 20 mg once daily

• review after 1-2 weeks before any increase
• check BP, nausea, appetite, sleep, mood/behavior, and suicidality
• avoid in significant hepatic dysfunction or severe renal impairment
• do not stop abruptly after regular use

3. Tramadol 50 mg three times daily

• Tramadol and duloxetine are both serotonergic. The combination increases the risk of serotonin toxicity. Tramadol is specifically listed among medicines associated with serotonin syndrome when used with SNRIs such as duloxetine. The Harriet Lane Handbook, p. 302.
• Tramadol plus pregabalin increases risks of sedation and respiratory depression. The FDA advises starting gabapentinoids at the lowest dose and monitoring for sedation and respiratory depression when they are co-prescribed with opioids. See the FDA gabapentinoid warning.
• Tramadol may worsen constipation and urinary retention, both relevant in vincristine autonomic neuropathy.
• It lowers the seizure threshold, which matters in a patient receiving cancer treatment and potentially other interacting drugs.

Safer practical adjustment

1. Continue pregabalin with close monitoring, assuming renal function is normal.
2. Use either duloxetine or tramadol, rather than routinely prescribing both at initiation.
3. If pain is severe enough to require opioid rescue while pregabalin is titrated:
   • involve pediatric oncology/pain or palliative care
   • use the lowest effective opioid for the shortest period
   • ensure a bowel plan and sedation/respiratory monitoring
   • reassess at least daily if inpatient

Monitoring required now

• Sedation score and respiratory rate, especially overnight
• Oxygen saturation if inpatient or if drowsy
• New agitation, tremor, sweating, diarrhea, fever, hyperreflexia, inducible clonus, or confusion suggesting serotonin toxicity
• Bowel chart and abdominal distension
• Post-void residual if urinary symptoms persist or worsen
• Renal function before and during pregabalin
• Daily pain score and allodynia assessment
• Neurologic progression, since analgesic sedation must not obscure worsening weakness or cord-compression signs

Preferred add-on for the touch-evoked foot pain

• It may reduce focal allodynia with minimal systemic adverse effects.
• Use the locally available pediatric formulation, such as lidocaine 4% gel/cream or a cut patch, according to product age limits and institutional policy.
• Do not use on broken, infected, inflamed, or irradiated skin.
• Avoid heat over the area.
• It is preferable to Neurobion cream, which has no established benefit for chemotherapy-induced neuropathic pain.

For non-neuropathic or musculoskeletal pain

• 10-15 mg/kg per dose orally every 4-6 hours as needed
• For 45 kg: 450-675 mg per dose
• Do not exceed the local pediatric maximum daily dose, and include all combination products when calculating the total.

If pain remains severe despite pregabalin + duloxetine + topical lidocaine

• 0.1-0.2 mg/kg per dose every 4 hours as needed
• This corresponds to approximately 5 mg oral morphine per rescue dose initially, with careful titration only by the treating service.

A reasonable sequence for this patient

1. Continue pregabalin 75 mg twice daily if alertness and renal function permit.
2. Continue low-dose duloxetine 20 mg daily only with monitoring, but withdraw scheduled tramadol unless the pediatric pain team has a compelling reason to retain it.
3. Add topical lidocaine for focal foot allodynia.
4. Add paracetamol as needed for accompanying nociceptive pain.
5. If still severe, use monitored short-acting morphine rescue, rather than tramadol.
6. Check constipation, post-void residual, sedation, and respiratory status daily.

Suggested PRN approach

• Oral immediate-release morphine 2.5 to 5 mg PRN
• A practical initial dose is 5 mg orally for severe breakthrough pain, with reassessment of pain, sedation, and respiratory rate.
• The repeat interval should follow the hospital pediatric pain protocol, commonly every 4 hours PRN for an opioid-naive patient. Earlier repeat dosing should only be under an inpatient pediatric pain/oncology protocol with reassessment.

Important: stop tramadol

Monitoring and safeguards

• Monitor sedation score, respiratory rate, oxygen saturation, and BP after doses, especially overnight.
• Hold opioid and seek urgent review for excessive drowsiness, difficult arousal, reduced respiratory rate, or oxygen desaturation.
• Ensure naloxone is available in the inpatient setting.
• Start bowel prophylaxis if repeated morphine doses are needed, and monitor for constipation, abdominal distension/ileus, and urinary retention.
• Check renal function. Morphine metabolites accumulate in renal impairment, so use a lower dose or choose an alternative opioid with the pain team if renal function is reduced.

If tramadol was started only recently

If tramadol has been given regularly for more than 1-2 weeks

• Days 1-2: tramadol 50 mg twice daily, total 100 mg/day
• Days 3-4: tramadol 50 mg once daily
• Then stop

When to stop immediately

• Serotonin toxicity: agitation, confusion, sweating, fever, diarrhea, tremor, hyperreflexia, inducible clonus
• Seizure
• Marked sedation, respiratory depression, or severe ileus/urinary retention
• Allergy/anaphylaxis

During the switch

• Continue pregabalin if alertness and renal function allow.
• Continue duloxetine 20 mg daily only with monitoring, but do not up-titrate it during the tramadol transition.
• If analgesic rescue is necessary, use a non-serotonergic alternative, such as immediate-release morphine, under the pediatric oncology/pain service. Do not give PRN tramadol on top of morphine.
• Monitor for tramadol withdrawal: anxiety, restlessness, sweating, rhinorrhea, nausea/vomiting, diarrhea, abdominal cramps, tremor, insomnia, and transient worsening pain.
• Morphine can treat pain, but it may not fully prevent the atypical SNRI-like symptoms sometimes seen during tramadol withdrawal.

1. Monitor for serotonin toxicity

Check at least each nursing shift, and after any dose increase

• Temperature
• Heart rate and BP
• Respiratory rate
• Mental state: anxiety, agitation, confusion, delirium
• Sweating/diaphoresis
• Nausea, vomiting, diarrhea
• Tremor or muscle jerks
• Inducible ankle clonus: rapidly dorsiflex the foot and look for repetitive beats
• Ocular clonus: abnormal repetitive eye movements
• Reflexes, especially lower limbs
• Tone/rigidity

Suspect serotonin toxicity if a serotonergic exposure is present and any Hunter feature occurs

• Spontaneous clonus, or
• Inducible clonus plus agitation or sweating, or
• Ocular clonus plus agitation or sweating, or
• Tremor plus hyperreflexia, or
• Temperature >38 C plus hypertonia and inducible/ocular clonus

If suspected

1. Stop tramadol and hold duloxetine.
2. Do not add other serotonergic agents. Review ondansetron, metoclopramide, linezolid, dextromethorphan, SSRIs/SNRIs, and fentanyl exposure.
3. Urgent medical/pediatric oncology review.
4. Supportive care: IV access, fluids as indicated, external cooling for fever, ECG, and laboratory evaluation guided by severity.
5. If moderate/severe symptoms, transfer to a higher-monitoring setting. Benzodiazepines are often used by the treating team for agitation/tremor. Severe hyperthermia, rigidity, seizure, or declining consciousness requires PICU-level care.

2. Monitor for opioid sedation and respiratory depression

Before every morphine PRN dose

• Pain score and location
• Sedation/alertness score
• Respiratory rate, work/depth of breathing
• SpO2
• Heart rate and BP
• Last opioid dose and total doses in the preceding 24 hours
• Whether the patient received pregabalin or another sedative recently
• Renal function status, if available

After each oral immediate-release morphine dose

• 30-60 minutes after the dose: pain score, sedation score, respiratory rate, SpO2
• Reassess again at 2 hours
• Continue at least 4-hourly observations while repeat PRN opioid dosing is needed
• Use continuous pulse oximetry overnight or more intensive monitoring if there are repeat doses, oxygen requirement, renal impairment, respiratory illness, sleep apnea, marked fatigue, or concurrent CNS depressants.

Use a simple sedation scale

Escalate urgently if any of the following occur

• Difficult to rouse or sedation score 2 or 3
• Slow, shallow, irregular breathing or apnea
• Falling SpO2, cyanosis, or new oxygen requirement
• Pinpoint pupils with reduced consciousness
• New confusion, hypotension, or repeated vomiting with drowsiness
• New abdominal distension, severe constipation, urinary retention, or ileus symptoms

3. Medication-specific safeguards in this case

• Do not give morphine and tramadol together. If morphine PRN is adopted, withdraw tramadol as planned.
• Keep duloxetine at 20 mg daily during tramadol taper. Do not increase it until tramadol has been stopped and the patient is clinically stable.
• Continue pregabalin only if alertness is satisfactory and renal function is acceptable.
• Avoid benzodiazepines, sedating antihistamines, alcohol, and other CNS depressants unless specifically supervised.
• Track bowel output and perform a post-void residual if urinary symptoms persist. Both vincristine neuropathy and opioids can worsen bowel/bladder dysfunction.

If iatrogenic opioid sedation/hypoventilation occurs in a monitored ward setting

• 0.001-0.002 mg/kg IV initially, slowly
• For 45 kg: 0.045-0.09 mg IV, practically 0.04 mg to 0.1 mg IV
• Reassess after 2-3 minutes and repeat small increments as needed until respiratory rate, depth, and responsiveness are safe.

If there is severe toxicity

1. Call emergency/PICU/anesthesia help immediately.
2. Airway positioning, oxygen, bag-mask ventilation as required.
3. Use the emergency pediatric protocol. The labeled initial pediatric IV naloxone dose is 0.01 mg/kg:
   • For 45 kg: 0.45 mg IV
4. Repeat every 2-3 minutes if ventilation does not improve. A larger subsequent dose of 0.1 mg/kg may be used under resuscitation-team direction if inadequate response.

After any naloxone dose

• Stop/hold morphine, tramadol, pregabalin, and other sedatives pending urgent review.
• Continuous pulse oximetry and frequent respiratory/sedation observations.
• Monitor for recurrence for at least 2-4 hours, longer if repeated doses are needed, renal function is impaired, or a long-acting opioid is involved. Naloxone may wear off in 20-60 minutes while opioid effects persist.
• Have a plan for repeat naloxone or an infusion in PICU if repeated boluses are required.
• Document respiratory rate, SpO2, sedation score, dose/time of every opioid and naloxone dose, and reassess the analgesic plan.

• Continue pregabalin rather than switching immediately if pain is improving and there is no troublesome sedation, dizziness, confusion, edema, or worsening transfers.
• Pregabalin has convenient twice-daily dosing and more predictable absorption than gabapentin. It may be useful for severe burning pain and allodynia.
• Review response after several days before escalating. Adjust for renal impairment.

• pregabalin causes excessive sedation/dizziness or edema
• cost or access is an issue
• you want a more gradual, flexible titration in this neurologically impaired adolescent
• the local pediatric oncology/pain service has more experience with it.

Practical recommendation here

• Pregabalin 75 mg twice daily
• Duloxetine 20 mg once daily, without early escalation
• Stop/taper tramadol as discussed
• Use topical lidocaine for focal allodynia if appropriate
• Use monitored immediate-release morphine only as PRN rescue if required

NSAIDs

• Current platelet count is adequate and stable
• No active bleeding, bruising, mucositis, gastritis, or GI bleeding
• Normal or acceptable renal function and hydration
• No significant hepatic dysfunction
• No sepsis or high bleeding risk
• No imminent lumbar puncture/procedure
• No concurrent anticoagulant or antiplatelet medicine
• No relevant interaction with the chemotherapy phase, especially high-dose methotrexate, where NSAIDs can impair methotrexate clearance and increase toxicity

Dexamethasone

• Steroid myopathy, which can worsen or confuse assessment of weakness
• Hyperglycemia
• Mood/behavioral effects and insomnia
• Infection risk
• Hypertension
• Gastritis/GI bleeding, especially if combined with an NSAID
• Masking of fever/infection

When dexamethasone is appropriate

Bottom line for this case

• If confirmed VIPN without compression: no dexamethasone for pain or neuropathy.
• NSAID: only if there is a clearly separate nociceptive pain component and current CBC/renal function/chemotherapy schedule permit it.
• Avoid NSAID plus dexamethasone unless there is a compelling indication and gastroprotection/bleeding surveillance is in place.
• Continue urgent reassessment of bladder symptoms and motor deficit, because progression would shift management toward suspected cord compression rather than analgesic escalation.

Where might the combination ever be used?

• alternatives are ineffective or unsuitable
• a pain specialist explicitly accepts the interaction risk
• both drugs are at stable low doses
• no other serotonergic drugs, seizure risk, renal/hepatic impairment, or respiratory-risk factors are present
• close monitoring is feasible

In this patient

• adolescent age and off-label neuropathic-pain use
• pregabalin co-treatment, which adds sedation with opioids
• urinary symptoms/possible autonomic neuropathy
• potential constipation and seizure risk from tramadol

Preferred approach

• Continue one neuropathic agent strategy, such as pregabalin with cautiously introduced duloxetine if the oncology/pain team agrees.
• Taper/stop tramadol if it has been regularly used beyond a few days.
• For severe breakthrough pain, prefer short-acting immediate-release morphine PRN under pediatric oncology/pain supervision, rather than tramadol.
• Add clinician-approved topical lidocaine for localized foot allodynia if skin is intact.

Epidural or intrathecal analgesia

Not first-line in this case

• Bilateral motor neuropathy and urinary symptoms, with cord/cauda equina pathology not yet fully excluded
• A possible chemotherapy-related fall in platelets and/or coagulation problems
• Immunosuppression and risk of bacteremia or infection
• A need for frequent reliable lower-limb neurologic examinations
• Potential autonomic neuropathy, which an epidural can worsen through hypotension and urinary retention

When could an epidural/intrathecal technique be considered?

• MRI has excluded cord compression and an evolving neurologic lesion
• Pain is stable, severe, and poorly controlled despite multimodal medication
• Platelets/coagulation are acceptable and stable
• There is no bacteremia, sepsis, local infection, or expected profound cytopenia
• Neurologic monitoring is still feasible

Peripheral nerve blocks

• The symptoms are likely bilateral and length-dependent, so the block would need to be repeated/bilateral and may still be incomplete.
• It can cause additional sensory and motor block, impair transfers, and increase falls or injury risk.
• Existing peripheral neuropathy may increase the risk of prolonged or permanent sensorimotor deficit after regional anesthesia. Morgan and Mikhail's Clinical Anesthesiology, risks and contraindications section.
• A block can conceal worsening sensory or motor deficits if cord pathology is not conclusively excluded.

More appropriate interventional-adjunct options

1. Topical lidocaine
   Most reasonable for focal touch-evoked pain over intact foot skin. It can reduce superficial allodynia without causing motor block.
2. Desensitization therapy through physiotherapy/occupational therapy
   Very light graded tactile exposure, soft fabrics, texture progression, positioning, and footwear modification. Avoid forceful massage over painful allodynic areas.
3. TENS
   May be trialed by physiotherapy/pain services if the skin is intact and there is no contraindication. Evidence in VIPN is limited, but risk is relatively low.
4. Specialist inpatient ketamine infusion
   This can be considered by a pediatric pain/anesthesia service for severe refractory neuropathic cancer pain when standard therapy is ineffective or opioid escalation is unsafe. It is not a routine ward treatment and requires protocolized monitoring.

Recommendation for this case

1. Obtain or confirm urgent MRI if there is any ongoing concern for spinal compression.
2. Check current CBC with platelets, coagulation profile if indicated, renal/liver function, infection markers, and medication interactions.
3. Optimize noninvasive therapy: pregabalin or gabapentin, cautious duloxetine use, topical lidocaine, rehabilitation/desensitization, and limited monitored morphine rescue if necessary.
4. Refer to pediatric pain-anesthesia/palliative care if pain remains severe.

When to consider it in this case

• Urgent cord/cauda equina compression and another evolving neurologic cause have been excluded or are being actively managed.
• Pain remains severe despite optimized pregabalin, cautious duloxetine use, topical lidocaine for focal allodynia, and appropriate PRN opioid rescue.
• The patient is admitted to a monitored setting with a pediatric acute-pain/palliative-care team.
• A current medication review has excluded avoidable sedatives and drug interactions.
• Baseline observations and mental state are documented.

A cautious example starting regimen

• Avoid a loading bolus in this setting. A bolus increases dysphoria, hallucinations, hypertension, and nausea, and is not needed for a cautious neuropathic-pain trial.
• Start ketamine 0.05 mg/kg/hour IV continuous infusion.
  • For 45 kg: 2.25 mg/hour
• Assess pain and adverse effects after 30-60 minutes.
• If inadequate and well tolerated, increase by 0.025-0.05 mg/kg/hour at intervals defined by the local pediatric pain protocol.
  • Typical low-dose analgesic range: 0.05-0.2 mg/kg/hour
  • For 45 kg: 2.25-9 mg/hour
• Do not exceed the local service maximum. Some centers use up to 0.3 mg/kg/hour, but higher doses need more intensive specialist monitoring.

• pain score and allodynia
• function and sleep
• opioid requirement
• adverse effects

Monitoring

• Continuous pulse oximetry
• Respiratory rate, heart rate, BP, and sedation score
• Pain score and neurological examination
• Mental status for anxiety, agitation, dysphoria, hallucinations, confusion, or delirium
• Nausea/vomiting and excessive salivation
• Monitor at least every 15 minutes initially and after a change in rate, then according to the pediatric pain-service protocol once stable.

What to do with current analgesics

• Stop/taper tramadol. Ketamine does not justify continuing tramadol with duloxetine.
• Continue pregabalin only if the patient is alert and renal function is acceptable.
• Keep duloxetine 20 mg daily stable, without dose escalation during the ketamine trial.
• Continue a small-dose immediate-release morphine PRN initially, but reassess and reduce opioid use if ketamine is effective.
• Avoid routinely adding benzodiazepines or sedating antihistamines, because they can obscure neurologic assessment and add sedation. If severe ketamine dysphoria occurs, the pain/anesthesia team should manage it.

Do not start, or stop and seek specialist review, if there is

• Uncontrolled hypertension, tachyarrhythmia, or serious cardiac disease
• Active psychosis, severe delirium, or inability to assess mental status
• Uncontrolled seizures
• Significant hepatic dysfunction, especially if an infusion may be prolonged
• Major unexplained rise in intracranial pressure or an unstable CNS condition
• Severe agitation or hallucinations during infusion
• Any new neurologic deterioration, urinary retention, sensory level, or worsening bilateral weakness

Bottom line

Ketamine IV infusion 0.05 mg/kg/hour, no bolus, using an infusion pump, inpatient continuous monitoring; titrate only under pediatric pain/anesthesia review to a usual maximum of 0.2 mg/kg/hour.