Tylenol 3 Strength
Tylenol 3 contains 300 mg of acetaminophen combined with 30 mg of codeine phosphate per tablet. 1
Standard Formulation
The standard formulation of Tylenol 3 (acetaminophen with codeine phosphate) consists of:
- Acetaminophen: 300 mg
- Codeine phosphate: 30 mg (equivalent to approximately 22.5 mg codeine base)
This combination is classified as a WHO Step II analgesic for moderate pain (numerical pain score 4-6). 2, 3
Dosing Parameters
Typical dosing: 1-2 tablets every 4 hours as needed, not to exceed the maximum daily acetaminophen dose. 1
Maximum daily acetaminophen limits:
- General population: 4000 mg per day 4, 5
- FDA recommendation: Consider limiting to 3000 mg per day for chronic use 4
- Patients with liver disease: 2000-3000 mg per day 2
Maximum codeine dose: Up to 240 mg per day 3
Clinical Context
Relative Potency
Codeine has approximately 1/10th the potency of morphine (relative effectiveness: 0.1-0.2 compared with oral morphine). 2 This makes it a weak opioid suitable for moderate pain that has not responded adequately to non-opioid analgesics alone.
Important Metabolic Considerations
Codeine requires hepatic metabolism via CYP2D6 to convert to morphine for analgesic effect. 2, 1 This creates significant variability:
- Ultra-rapid metabolizers (1-28% depending on ethnicity) convert codeine to morphine too quickly, risking life-threatening respiratory depression even at standard doses 1
- Poor metabolizers may experience inadequate analgesia
- Patients with liver cirrhosis should avoid codeine entirely, as metabolites accumulate causing respiratory depression 2
Comparative Efficacy
Recent evidence challenges the superiority of Tylenol 3:
- No clinically significant difference in pain relief compared to acetaminophen alone or NSAIDs for acute extremity pain 6, 7
- Hydrocodone/acetaminophen showed only marginal superiority over codeine/acetaminophen (0.4 NRS units difference, not clinically significant) 6
- Higher adverse event rates with codeine combinations (64% vs 34% with NSAIDs alone), including drowsiness, dizziness, nausea/vomiting 8, 9
Critical Safety Warnings
Contraindications per FDA labeling: 1
- Severe asthma or respiratory problems
- Bowel obstruction
- Children post-tonsillectomy/adenoidectomy (risk of fatal respiratory depression in ultra-rapid metabolizers)
- Nursing mothers (codeine passes into breast milk as morphine)
Black box warnings include risks of: 1
- Opioid addiction, abuse, and misuse leading to overdose and death
- Life-threatening respiratory depression
- Accidental ingestion (especially in children)
- Neonatal opioid withdrawal syndrome with prolonged use in pregnancy
Practical Prescribing Considerations
Given the limited evidence of superior efficacy over non-opioid alternatives and the significant safety concerns, Tylenol 3 should be reserved for patients with moderate pain where acetaminophen or NSAIDs alone are contraindicated or have failed. 8 When prescribed, use the lowest effective dose for the shortest duration, typically no more than 3-7 days for acute pain. 4, 8
The FDA has moved to limit acetaminophen in combination products to 325 mg per dosage unit to reduce hepatotoxicity risk, though the traditional 300 mg formulation of Tylenol 3 predates this recommendation. 4, 5