Codeine Plus Acetaminophen for Pain After Photorefractive Keratectomy: A Randomized, Double-Blind, Placebo-Controlled Add-On Trial

Background: Pain after photorefractive keratectomy (PRK) is significant, and the analgesic efficacy and safety of oral opioids in combination with acetaminophen has not been fully investigated in PRK trials. Purpose: To assess the efficacy and safety of the combination of codeine plus acetaminophen (paracetamol) versus placebo as an add-on therapy for pain control after PRK. Study design: Randomized, double-blind, placebo-controlled trial. Setting: Single tertiary center. Methods: One eye was randomly allocated to the intervention, whereas the fellow eye was treated with a placebo. Eyes were operated 2 weeks apart. The participants were adults older than 20 years with refractive stability for ≥1 year, who underwent PRK for correction of myopia or myopic astigmatism. Codeine (30 mg) plus acetaminophen (500 mg) was given orally 4 times per day for 4 days after PRK. The follow-up duration was 4 months. The study outcomes included pain scores at 1 to 72 hours, as measured by the visual analog scale, McGill Pain Questionnaire, and Brief Pain Inventory, as well as adverse events and corneal wound healing. Results: Of the initial 82 eyes, 80 completed the trial (40 intervention, 40 placebo). Median (interquartile range) pain scores as measured by the visual analog scale were statistically and clinically lower during treatment with codeine/acetaminophen compared with the placebo: 1 hour: 4 (2–4) versus 6 (3–6), P < 0.001; 24 hours: 4 (3–6) versus 7 (6–9), P < 0.001; 48 hours: 1 (0–2) versus 3 (2–5), P < 0.001; and 72 hours: 0 (0–0) versus 0 (0–2), P = 0.001. Virtually identical results were obtained by the McGill Pain Questionnaire and Brief Pain Inventory scales. The most common adverse events with codeine/acetaminophen were drowsiness (42%), nausea (18%), and constipation (5%). No case of delayed epithelial healing was observed in both treatment arms. Conclusions: When added to the usual care therapy, the oral combination of codeine/acetaminophen was safe and significantly superior to the placebo for pain control after PRK. Clinical Trial Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02625753.