Cancer Chemotherapy Side Effects and Mechanism

Analgesics and Pain Management

• Celecoxib: contraindicated in patients with sulfonamide allergy, most potent COX-2 inhibitor

Skeletal Muscle Relaxants

• Baclofen (Lioresal): high abuse potential
• Carisoprodol (Soma): high abuse potential
• Tizanidine (Zanaflex): interacts with benzodiazepines and opioids, barbiturates
• Cyclobenzaprine (Flexiril): interacts with benzodiazepines and opioids, barbiturates

Antidepressants

• Duloxetine (Cymbalta): blocks reuptake of norepinephrine, used for neuropathic pain, takes 1-2 weeks for effect, recommended to be taken in the morning to prevent insomnia, serious adverse effects: SIADH

Anticonvulsants

• Gabapentin (Neurontin, Gralise, Horizant): blocks presynaptic release of calcium, reducing release of excitatory amino acids, used for postherpetic neuralgia, neuropathic, chronic, and postoperative pain, restless leg syndrome, common side effects: peripheral edema, weight gain

Topical Agents

• Lidocaine (Lidoderm): 4% strength OTC, 5% strength Rx, calms neuronal membrane, used for postherpetic neuralgia, relief of localized pain, adverse effects: application site reactions, no more than 3 patches can be applied at 1 time

Chemotherapy Agents

• Ifosfamide/cyclophosphamide: causes hemorrhagic cystitis, prevention: Mesna, hydration
• Anthracyclines: incorporates with DNA base pairs, inhibits DNA and RNA synthesis, causes cardiac toxicity, severe side effects: cardiac toxicity
• Antiandrogen: disrupts androgen production, affects androgen activity, testosterone is the main androgen hormone, CYP17 enzyme inhibitors: Abiraterone (Zytiga), dosing: 1000 mg once daily with prednisone 5 mg twice daily, common side effects: hot flashes, fatigue, hypertriglyceridemia, joint swelling, hyperglycemia, counseling points: take on an empty stomach, swallow tablet whole, do not crush or chew

Antiestrogen

• MOA: selective estrogen receptor modulators, competes with estrogen for binding sites, antagonist effect on breast tissue, patches may be cut into smaller sizes, apply patches only once for up to 12 hours in 24 hours

Opioid Analgesics

• Opioid MOA: targets Mu, Kappa, and Delta opioid receptors, alters perception and response to pain
• Mu (μ) receptor: found primarily in the brainstem and thalamus, responsible for supraspinal analgesia
• Kappa (κ) receptor: found in the limbic and other diencephalic areas, brainstem, and spinal cord, effects not well-studied
• Delta (δ) receptor: responsible for spinal analgesia
• Adverse effects of opioids: constipation, nausea, vomiting, respiratory depression, sedation, euphoria, pruritis, physical dependence
• Tramadol: additional MOA: inhibits serotonin and norepinephrine reuptake, warnings: seizure risk, serotonin syndrome risk
• Ultracet: tramadol in combination with acetaminophen
• Codeine: gets metabolized to morphine by CYP2D6, additional boxed warnings: respiratory depression and death in children who are ultra-rapid metabolizers, contraindications: children < 12 years of age
• Tylenol #3: 30 mg of codeine, Tylenol #4: 60 mg of codeine
• Morphine: additional boxed warnings: medication errors with oral solution, may cause pruritis, gets further metabolized to M6G and M3G, be careful with patients with renal impairment
• Hydrocodone: additional boxed warnings: initiation of CYP3A4 inhibitors can cause fatal overdose, dosing: Q12H, Zohydro ER capsule, Norco (short-acting), Tussionex (oral solution)
• Oxycodone: additional boxed warnings: initiation of CYP3A4 inhibitors can cause fatal overdose, caution with oxycodone oral solution and oral concentrate, Xtampza ER (abuse deterrent formulation), Percocet (short-acting)
• Fentanyl: additional boxed warnings: potential for medication errors when converting between different dosage forms, use with strong or moderate CYP3A4 inhibitors may result in increased effects and fatal respiratory depression, available in numerous dosage forms except for an oral tablet