A composition for use in a method of treating pain in a subject in need of analgesic relief, the composition comprising an oral formulation comprising: (a) a unit dose of acetaminophen and (b) a therapeutic efficacy-enhancing amount of N-acetylcysteine; wherein a total of all unit doses to be administered per day according to said method is an amount less than a standard maximum daily dose of acetaminophen, wherein the standard maximum daily dose of acetaminophen is: 200 mg for a subject 0-3 months of age, 2.72-4.99 kg (6-11 lb) body weight, receiving 40 mg/dose; 400 mg for a subject 4-11 months of age, 5.44-7.71 kg (12-17 lb) body weight, receiving 80 mg/dose; 600 mg for a subject 12-23 months of age, 8.16-10.43 kg (18-23 lb) body weight, receiving 120 mg/dose; 800 mg for a subject 2-3 years of age, 10.89-15.85 kg (24-35 lb) body weight, receiving 160 mg/dose; 1200 mg for a subject 4-5 years of age, 16.33-21.32 kg (36-47 lb) body weight, receiving 240 mg/dose; 1600 mg for a subject 6-8 years of age, 21.77-26.76 kg (48-59 lb) body weight, receiving 320 mg/dose; 1625 mg for a subject 6-11 years of age, receiving 325 mg/dose; 2000 mg for a subject 9-10 years of age, 27.22-32.21 kg (60-71 lb) body weight, receiving 400 mg/dose; 2400 mg for a subject 11 years of age, 32.66-43.09 kg (72-95 lb) body weight, receiving 480 mg/dose; 3200 mg for a subject 12 years of age, 43.55 kg (96 lb) body weight receiving 640 mg/dose; 4000 mg for a subject >12 years of age to adult, receiving 650 mg/dose; 4000 mg for a subject >12 years of age to adult, receiving 500 mg/dose; wherein (i) acetaminophen and N-acetylcysteine are present in the composition in a molar ratio of acetaminophen to N-acetylcysteine ranging from 1:15 to 1:0.000977; and (ii) the formulation is effective to provide pain relief equivalent to a standard maximum daily dose of acetaminophen. (a) a unit dose of acetaminophen and (b) a therapeutic efficacy-enhancing amount of N-acetylcysteine; 200 mg for a subject 0-3 months of age, 2.72-4.99 kg (6-11 lb) body weight, receiving 40 mg/dose; 400 mg for a subject 4-11 months of age, 5.44-7.71 kg (12-17 lb) body weight, receiving 80 mg/dose; 600 mg for a subject 12-23 months of age, 8.16-10.43 kg (18-23 lb) body weight, receiving 120 mg/dose; 800 mg for a subject 2-3 years of age, 10.89-15.85 kg (24-35 lb) body weight, receiving 160 mg/dose; 1200 mg for a subject 4-5 years of age, 16.33-21.32 kg (36-47 lb) body weight, receiving 240 mg/dose; 1600 mg for a subject 6-8 years of age, 21.77-26.76 kg (48-59 lb) body weight, receiving 320 mg/dose; 1625 mg for a subject 6-11 years of age, receiving 325 mg/dose; 2000 mg for a subject 9-10 years of age, 27.22-32.21 kg (60-71 lb) body weight, receiving 400 mg/dose; 2400 mg for a subject 11 years of age, 32.66-43.09 kg (72-95 lb) body weight, receiving 480 mg/dose; 3200 mg for a subject 12 years of age, 43.55 kg (96 lb) body weight receiving 640 mg/dose; 4000 mg for a subject >12 years of age to adult, receiving 650 mg/dose; 4000 mg for a subject >12 years of age to adult, receiving 500 mg/dose; wherein (i) acetaminophen and N-acetylcysteine are present in the composition in a molar ratio of acetaminophen to N-acetylcysteine ranging from 1:15 to 1:0.000977; and (ii) the formulation is effective to provide pain relief equivalent to a standard maximum daily dose of acetaminophen. (i) acetaminophen and N-acetylcysteine are present in the composition in a molar ratio of acetaminophen to N-acetylcysteine ranging from 1:15 to 1:0.000977; and (ii) the formulation is effective to provide pain relief equivalent to a standard maximum daily dose of acetaminophen.