13.2 Rehabilitation Pharmacology & Medication Management

Rehabilitation Pharmacology & Medication Management

Pharmacology is a Domain A applied-science topic with high clinical yield. The physiatrist prescribes and coordinates medications for spasticity, pain, bladder/bowel, bone, and psychiatric comorbidity, recognizing adverse effects and interactions that affect rehabilitation.

Antispasticity Medications

Intrathecal baclofen screening trial precedes pump implant; withdrawal is a medical emergency (fever, spasticity rebound, rhabdomyolysis) managed with oral baclofen and supportive care.

Neuropathic Pain Agents

First-line:  Gabapentin/Pregabalin (alpha-2-delta Ca channel)  OR  TCA (nortriptyline)  OR  SNRI (duloxetine)
Second-line/adjunct:  Topical lidocaine/capsaicin, tramadol, opioids (not first-line; risks)

• Gabapentinoids: renal dose adjustment; sedation, dizziness, edema.
• TCAs: anticholinergic, QT, sedation; nortriptyline preferred for fewer side effects than amitriptyline.
• SNRIs (duloxetine): useful for diabetic neuropathy and fibromyalgia; monitor BP.
• Opioids: not first-line; risks (dependency, OSA, hypogonadism) — opioid stewardship.

Bladder & Bowel Medications

• Detrusor overactivity (urge/neurogenic): anticholinergics (oxybutynin, tolterodine, solifenacin) — anticholinergic burden (cognition in elderly); beta-3 agonist (mirabegron) — less cognitive burden; intravesical botulinumtoxinA; intermittent catheterization when retention coexists.
• Outlet incompetence (stress): pseudoephedrine, duloxetine, or surgical sling.
• Retention: bethanechol (post-op/postpartum), alpha-blockers (tamsulosin) for bladder outlet.
• Bowel: stimulant (senna, bisacodyl), osmotic (polyethylene glycol, lactulose), stool softener; rectal stimulant for neurogenic bowel program.

Bone & Other

• Bisphosphonates, denosumab, teriparatide, romosozumab for osteoporosis (see bone-health section).
• NSAIDs: renal, GI, cardiovascular risk; combine with PPI in high-risk; avoid in CKD and late pregnancy.
• Anticoagulants: warfarin, DOACs (apixaban, rivaroxaban) for VTE prophylaxis in immobilized patients; NSAIDs and antiplatelets increase bleeding risk.
• Antidepressants/anxiolytics: SSRIs/SNRIs commonly; sedating agents impair rehab participation.

Drug Interactions & Withdrawal Cautions

• Baclofen + alcohol/sedatives → profound CNS depression; abrupt baclofen withdrawal → seizures.
• NSAIDs + warfarin/SSRIs → bleeding; NSAIDs + ACE inhibitors/diuretics → renal injury.
• Prolonged QT drugs combined (e.g., TCAs + certain antiemotics) → arrhythmia risk.
• Sudden corticosteroid cessation → adrenal insufficiency; taper prolonged courses.

Chemodenervation Dosing & Pitfalls

OnabotulinumtoxinA dosing balances efficacy and antibody formation; frequent, high-dose, "booster" injections increase neutralizing antibody risk and secondary nonresponse. Toxin choice matters: onabotulinumtoxinA, abobotulinumtoxinA, and incobotulinumtoxinA are not dose-equivalent (units differ by product). Common pitfalls include inadequate muscle selection (use EMG/ultrasound guidance), underdosing large muscles, and overlooking focal vs generalized spasticity patterns. Anterior neck injection risks dysphagia; limb injection risks excessive weakness impairing function—functional goals (hygiene, gait, pain) guide target selection, not tone reduction alone.

Intrathecal Baclofen: Screening & Emergency

ITB candidates undergo a screening bolus; a positive response (reduced tone/spasms) precedes pump implant. Complications: catheter breakage/kinking, pump malfunction, infection, CSF leak, and—critically—withdrawal (fever, spasticity rebound, rhabdomyolysis, autonomic instability) and overdose (hypotonia, respiratory depression, coma). ITB withdrawal is a medical emergency managed with oral baclofen/lorazepam and supportive care; overdose may require antidotal supportive care. Candidates should recognize the clinical patterns of ITB withdrawal and overdose.

Polypharmacy & Beers Criteria in Rehab

Rehab patients are often elderly with multiple medications. The Beers Criteria flag potentially inappropriate medications: benzodiazepines, first-generation antihistamines, anticholinergics, long-acting sulfonylureas, and NSAIDs in certain populations—each impairing rehab (sedation, falls, cognition, hypoglycemia, renal/GI bleeding). The physiatrist reconciles medications, deprescribes deliriogenic agents, and selects safer alternatives (e.g., mirabegron over oxybutynin in cognitively impaired elderly for bladder).

Medication Effects on Rehabilitation Participation

Coordinating pharmacotherapy with rehabilitation goals—timing sedating agents at night, minimizing cognitive load, adjusting for renal/hepatic function—optimizes outcomes and is a high-yield physiatric competency.

Corticosteroids in Rehabilitation

Corticosteroids are used acutely for MS relapse (high-dose intravenous methylprednisolone), spinal cord injury, and many inflammatory and pain conditions, and the physiatrist must weigh their rehabilitation-relevant adverse effects: a proximal steroid myopathy that directly undermines strength and transfer goals, hyperglycemia, fluid retention, hypertension, mood and sleep disturbance, peptic-ulcer risk that rises sharply when combined with NSAIDs, increased infection susceptibility, and avascular necrosis. Prolonged courses suppress the hypothalamic-pituitary-adrenal axis and require tapering rather than abrupt cessation to avoid adrenal crisis; bone loss accrues with chronic use, warranting calcium, vitamin D supplementation, and DEXA surveillance. Short high-dose pulses for relapse are generally well tolerated and are coordinated with the neurology service. The physiatrist pairs steroid therapy with protective rehabilitation—counteracting myopathy with graded resistive exercise, monitoring glucose and blood pressure, and timing therapy activity to the dosing schedule to minimize participation loss.