12.2 Analgesics & NSAIDs

Paracetamol

Paracetamol (acetaminophen) is the first-line analgesic for mild-to-moderate dental pain. Its mechanism is primarily central cyclooxygenase (COX) inhibition in the brain and spinal cord, with weak peripheral action. Unlike NSAIDs, it has little anti-inflammatory effect.

Paracetamol is generally safe in pregnancy, renal impairment, and with anticoagulants — features that make it attractive for dental patients with comorbidities.

NSAIDs (Non-Steroidal Anti-Inflammatory Drugs)

NSAIDs inhibit peripheral COX-1 and COX-2, reducing prostaglandin synthesis. This provides analgesic and anti-inflammatory action, making them effective for the inflammatory component of dental pain.

Common Agents in Dental Practice

Adverse Effects of NSAIDs

• Gastrointestinal bleeding — prostaglandin inhibition removes the protective mucus barrier; risk highest in elderly, history of ulcer, and with anticoagulants. Use a proton pump inhibitor (PPI) for at-risk patients.
• Renal impairment — prostaglandins maintain renal blood flow; NSAIDs reduce GFR, especially in dehydrated patients, the elderly, and those on ACE inhibitors or diuretics.
• Asthma exacerbation — 5–20% of asthmatics experience bronchospasm with NSAIDs. Samter's triad is asthma, nasal polyps, and aspirin/NSAID sensitivity.
• Platelet inhibition — reversible COX-1 blockade reduces platelet aggregation; additive with anticoagulants.
• Pregnancy — avoided in the third trimester (premature closure of the ductus arteriosus); avoid under 30 weeks unless essential; contraindicated in infants under 6 months.

NSAID Contraindications Summary

1. Active or history of peptic ulcer disease
2. Significant renal impairment (eGFR <30)
3. Concurrent anticoagulant therapy (warfarin, DOACs)
4. Known NSAID-sensitive asthma (Samter's triad)
5. Pregnancy third trimester
6. Infants under 6 months
7. Severe heart failure

Opioids

Opioids act on mu receptors in the central nervous system. They are used for moderate-to-severe dental pain when paracetamol and NSAIDs are insufficient.

Weak Opioids

• Codeine — pro-drug converted by CYP2D6 to morphine (about 5–10%). Poor metabolisers get limited analgesia. Main side effects: constipation, nausea, drowsiness. Useful as co-codamol (codeine + paracetamol).
• Dihydrocodeine — similar potency to codeine; 30 mg every 4–6 hours.
• Tramadol — 50–100 mg every 4–6 hours. Acts on mu receptors AND enhances serotonergic and noradrenergic pathways. Risk of seizures at high dose; serotonin syndrome when combined with SSRIs, SNRIs, or MAOIs. Avoid in epilepsy and withdrawing patients.

Strong Opioids

• Morphine — 10 mg every 4 hours orally; reserved for severe postoperative pain, usually in secondary care.

Opioid Side Effects

• Respiratory depression (dose-dependent; rare at therapeutic oral doses but important in sedation/elderly)
• Constipation (common with codeine)
• Nausea and vomiting
• Tolerance and dependence with prolonged use

WHO Analgesic Ladder

The World Health Organization ladder guides stepwise analgesic escalation:

Step 3: Strong opioid ± non-opioid ± adjuvant (severe pain)
  ↑
Step 2: Weak opioid ± non-opioid ± adjuvant (moderate pain)
  ↑
Step 1: Non-opioid (paracetamol ± NSAID) ± adjuvant (mild pain)

For acute dental pain, most patients need only steps 1 and 2. Postoperative dental pain typically lasts 48–72 hours; prescribe accordingly.

Dental Pain Evidence: Combination Analgesia

For acute dental pain, the most effective oral regimen is paracetamol combined with an NSAID (usually ibuprofen). The two drugs act via complementary central and peripheral mechanisms and produce additive or synergistic pain relief without opioid side effects.

Practical prescribing after a typical extraction: ibuprofen 400 mg three times daily plus paracetamol 1 g four times daily for 48 hours, then step down as pain allows.

Prescribing Cautions in the Dental Patient

• Anticoagulated patients (warfarin, DOACs): paracetamol is safe at standard doses; avoid NSAIDs (additive bleeding and INR effects with warfarin).
• Renal impairment: paracetamol safe; NSAIDs avoid or use briefly with monitoring.
• Elderly: start low, go slow; NSAID risk (GI, renal, cardiovascular) rises sharply with age.
• Pregnancy: paracetamol is first-line and safe; avoid NSAIDs in third trimester; opioids only if essential and short-term.
• Breastfeeding: paracetamol and ibuprofen are compatible; codeine is now contraindicated in breastfeeding mothers because ultra-rapid metabolisers expose the infant to morphine via breast milk.