What is the recommended pain medication regimen for an adult undergoing primary total hip arthroplasty?

Pain Management for Hip Replacement

For adults undergoing primary total hip arthroplasty, use a multimodal regimen consisting of scheduled paracetamol (acetaminophen) plus an NSAID or COX-2 inhibitor started pre-operatively and continued postoperatively, combined with intravenous dexamethasone 8-10 mg intra-operatively, and add a single-shot fascia iliaca block or local infiltration analgesia for regional pain control, reserving opioids strictly as rescue medication. 1, 2

Core Systemic Analgesics (Foundation of Pain Control)

The evidence-based foundation consists of three components that should be administered to all patients unless contraindicated:

1. Paracetamol (Acetaminophen)

• Administer pre-operatively or intra-operatively and continue postoperatively 1
• Both IV and oral formulations are effective, with no clinically significant difference between routes 1
• Provides safe reduction in postoperative pain and opioid consumption during hospitalization 3
• Continue as scheduled medication, not as-needed

2. NSAIDs or COX-2 Selective Inhibitors

• Start pre-operatively or intra-operatively and continue postoperatively 1
• Ibuprofen 1200 mg/day is most commonly used (typically 400 mg three times daily) 4
• Duration: 8 days for THA is standard practice 4
• COX-2 inhibitors (e.g., celecoxib, parecoxib) are equally effective alternatives with potentially lower GI risk 1
• Critical point: When NSAIDs/COX-2 inhibitors are used, adding paracetamol provides additional benefit, but paracetamol alone is insufficient 1

3. Intravenous Dexamethasone

• Single intra-operative dose of 8-10 mg IV 1, 2
• Provides both analgesic and anti-emetic effects 1
• No evidence supports repeated dosing; one dose is sufficient 1

Regional Analgesia Techniques

Add one regional technique, particularly for patients with contraindications to basic analgesics or anticipated high pain:

Preferred Options (Choose One):

Supra-inguinal Fascia Iliaca Compartment Block

• Most consistent evidence for motor-sparing analgesia 2
• Single-shot technique administered pre-operatively 1, 2
• Reduces opioid consumption at 24 and 48 hours 5
• Does not impair early mobilization 1

Pericapsular Nerve Group (PENG) Block

• Pre-operative administration recommended 2
• Newer technique with growing evidence base 2
• Motor-sparing properties facilitate early mobilization 2
• Caution: Rare reports of femoral nerve motor deficit (full recovery expected) 5

Local Infiltration Analgesia (LIA)

• Alternative when regional blocks unavailable or contraindicated 1, 2
• Single-shot technique performed intra-operatively by surgeon 1
• Significantly reduces pain at 4 hours postoperatively (VAS 1.6 vs 3.0 in controls) 5
• Improves patient satisfaction scores 5
• Reduces opioid consumption in first 24-48 hours 5

Techniques NOT Recommended:

Do not use the following due to adverse effects outweighing benefits:

• Femoral nerve block (causes motor blockade, delays mobilization) 1
• Lumbar plexus block (side effects exceed benefits) 1
• Quadratus lumborum block (inconsistent efficacy, motor weakness risk) 2
• Lumbar erector spinae plane block (inconsistent efficacy, motor weakness risk) 2
• Epidural analgesia (excessive side effects) 1
• Continuous catheter techniques for LIA (inconsistent evidence) 1

Intrathecal Morphine (Conditional Use)

If spinal anesthesia is used, intrathecal morphine 0.1 mg may be considered 1, 2, but:

• Only for hospitalized patients with monitoring capability 2
• The PROSPECT group emphasizes risks/side-effects (respiratory depression, pruritus, urinary retention, nausea) 1
• Adequate analgesia can be achieved with basic analgesics and regional techniques without intrathecal morphine 1
• Clinical decision: Reserve for patients where regional techniques are contraindicated and high pain is anticipated

Opioids: Rescue Only

Opioids should be reserved strictly as rescue analgesics postoperatively 1, 2

• Not part of scheduled regimen
• Use only when multimodal analgesia proves insufficient
• Patient-controlled analgesia (PCA) with fentanyl or morphine is acceptable for breakthrough pain 6
• Goal is opioid-sparing, not opioid-free (rescue opioids remain most common postoperative intervention) 7

Medications NOT Recommended:

• Gabapentinoids (pregabalin, gabapentin): Side effects outweigh benefits; increased CNS adverse events without consistent pain reduction 1
• Mirogabalin: No reduction in opioid consumption or pain; increased drowsiness/sedation (56.8% vs 28.3%) and headache 6
• Ketamine: Insufficient procedure-specific evidence 1

Practical Algorithm:

Pre-operative (in holding area):

1. Paracetamol 1000 mg PO
2. Ibuprofen 400 mg PO OR celecoxib 200 mg PO

Intra-operative:

1. Dexamethasone 8-10 mg IV (single dose)
2. Fascia iliaca block OR PENG block (pre-incision) OR LIA (surgeon performs at closure)
3. If spinal anesthesia used: Consider intrathecal morphine 0.1 mg (weigh risks/benefits)

Postoperative (scheduled):

1. Paracetamol 1000 mg PO every 6 hours
2. Ibuprofen 400 mg PO every 8 hours (continue for 8 days)
3. Opioid (e.g., oxycodone 5-10 mg PO) available as rescue PRN only

Common Pitfalls to Avoid:

1. Using paracetamol alone without NSAIDs/COX-2 inhibitors - inadequate analgesia 1
2. Routine gabapentinoid use - increases side effects without consistent benefit 1, 6
3. Femoral nerve blocks - causes motor blockade and delays mobilization 1
4. Scheduled opioids - should be rescue only 1
5. Omitting dexamethasone - single dose provides significant analgesic and anti-emetic benefit 1
6. Using intrathecal morphine without appropriate monitoring - respiratory depression risk 2

Special Considerations:

For patients with contraindications to NSAIDs (renal impairment, bleeding risk, cardiovascular disease):

• Regional technique becomes more important 1
• Consider COX-2 selective inhibitor if cardiovascular risk acceptable
• May need to accept higher rescue opioid use

For patients on chronic opioids or with high anticipated pain:

• Regional technique is strongly recommended 1
• Consider both fascia iliaca block AND LIA
• May require higher rescue opioid doses
• Note: The included studies did not assess this population specifically 1

The 2026 updated PROSPECT guidelines 2 reinforce the 2021 recommendations 1 with stronger evidence for supra-inguinal fascia iliaca block and PENG block as preferred regional techniques, while explicitly recommending against quadratus lumborum and erector spinae blocks due to motor weakness concerns.