Rescue Drugs for Osteoarthritis (OA) of the Knee

1. Oral Analgesics

Acetaminophen (Paracetamol)

• First-line oral analgesic for mild-to-moderate pain; strongly recommended by AAOS guidelines.
• Preferred in elderly and those with GI/cardiovascular risk that limits NSAID use.
• Maximum dose: 3-4 g/day; hepatotoxicity risk with overdose or alcohol use.

Oral NSAIDs

• Strongly recommended (AAOS 4-star) for moderate-to-severe pain.
• Examples: Ibuprofen, Naproxen, Diclofenac, Celecoxib (COX-2 selective).
• Celecoxib preferred in patients with GI risk; dose-equivalence with traditional NSAIDs for pain relief.
• Tramadol - a weak opioid/SEROTONIN-norepinephrine reuptake inhibitor - is specifically not recommended by AAOS for knee OA due to poor risk-benefit profile.
• Always use at the lowest effective dose for the shortest duration due to GI, cardiovascular, and renal risks.

2. Topical Agents

Topical NSAIDs

• Diclofenac gel/patch and Ketoprofen are strongly recommended (AAOS 4-star).
• Provide equivalent local pain relief to oral NSAIDs with much lower systemic absorption - preferred in elderly, those with comorbidities.
• First-choice pharmacologic option per ACR 2019 guidelines for patients with GI/cardiovascular concerns.

Topical Capsaicin

• Depletes substance P from sensory nerve terminals.
• Moderate evidence; burning/stinging on application is a common complaint.

3. Intra-articular (IA) Injections

IA Corticosteroids

• Moderately recommended (AAOS 3-star) for short-term relief.
• Agents: Triamcinolone acetonide, Methylprednisolone acetate, Betamethasone.
• Onset of action: within 1-2 days; duration: typically 4-8 weeks.
• Indicated in acute flare, presence of joint effusion, or when systemic drugs are contraindicated.
• Should not be given more than 3-4 times per year due to cartilage damage risk with repeated use.
• A 2025 systematic review (PMID 40028854) confirms IA corticosteroids provide reliable short-term relief but are outperformed at 6+ months by PRP, HA, and cell-based therapies.

IA Hyaluronic Acid (Viscosupplementation)

• Not recommended by AAOS (3-star against), though evidence remains debated.
• Agents: Sodium hyaluronate (Synvisc, Euflexxa, Orthovisc).
• ACR 2019 conditionally recommends it; some guidelines still use it as a rescue option when other therapies fail.
• Network meta-analysis (PMID 38331363) showed HA outperforms corticosteroids at ≥6 months.
• Hyaluronic acid health economics review 2024 (PMID 37899384) - cost-effectiveness data suggests benefit in select patients.

Platelet-Rich Plasma (PRP)

• Limited evidence (AAOS 2-star: may reduce pain/improve function).
• A 2024 network meta-analysis (PMID 38331363) found PRP, bone marrow aspirate concentrate, and HA all outperform corticosteroids beyond 6 months.
• Still considered investigational in many guidelines, but increasingly used as a rescue option.

Ozone Injections

• Emerging: a 2026 systematic review (PMID 41496305) confirmed ozone injections reduce pain in knee OA; evidence base is growing but not yet mainstream guideline-endorsed.

4. Opioids

• Not recommended by AAOS as a class (including Tramadol).
• Reserved as last resort when all other options have failed and surgery is not an option.
• Risk of addiction, falls, cognitive impairment (especially in elderly).
• Weak opioids (e.g., Codeine) may be used short-term in select cases under specialist supervision.

5. Duloxetine (Centrally Acting)

• A serotonin-norepinephrine reuptake inhibitor (SNRI); useful when there is a significant central sensitization component (neuropathic-type pain, burning/shooting symptoms).
• ACR 2019 conditionally recommends it, especially in patients with comorbid depression or anxiety.
• Not a first-line rescue drug but useful in patients unsuitable for NSAIDs.

Summary Table

• Miller's Review of Orthopaedics 9th Edition (AAOS Guidelines Table 5.7)
• Goldman-Cecil Medicine (Table 241-2, OA Management)
• Firestein & Kelley's Textbook of Rheumatology (Chapter 102, Approach to Management of OA)

Recent evidence note: A 2025 systematic review (PMID 40028854) indicates that PRP, bone marrow aspirate concentrate, and HA injections outperform corticosteroids at ≥6 months, shifting guideline thinking on IA therapy options.

Etoricoxib - Dosage Schedule

Dosage by Indication

For OA, the dose should start at 30 mg. If this provides insufficient relief, it may be stepped up to 60 mg. If 60 mg does not provide adequate benefit, other therapeutic options should be considered.

Key Pharmacokinetic Notes

• Half-life: ~22 hours - allows convenient once-daily dosing
• Onset: Faster when taken without food (useful when rapid relief is needed); may also be taken with food
• COX selectivity: COX-2 >> COX-1 (highly selective)
• In a large meta-analysis of single-dose oral analgesics, etoricoxib 120 mg ranked among the two most effective NSAIDs (alongside ketoprofen 25 mg) for acute pain relief - Current Surgical Therapy 14e

Dose Adjustments

Key Contraindications

• Active peptic ulcer/GI bleeding
• Severe heart failure (NYHA Class II-IV)
• Established ischemic heart disease, peripheral arterial disease, or cerebrovascular disease
• Uncontrolled hypertension (sustained BP >140/90 mmHg on therapy)
• Severe hepatic dysfunction
• CrCl <30 mL/min
• Pregnancy (especially ≥20 weeks) and breastfeeding
• Hypersensitivity to etoricoxib or sulfonamides
• Age <16 years

Important Prescribing Principle

• Firestein & Kelley's Textbook of Rheumatology (Table 59.1, Common NSAIDs)
• Etoricoxib SmPC - Arcoxia
• Johns Hopkins review - Etoricoxib clinical pharmacology