The most frequently observed reactions include lightheadedness, dizziness, drowsiness, headache, fatigue, sedation, sweating, nausea, vomiting, constipation, pruritus, and skin reactions. With the exception of constipation, tolerance develops to most of these effects. Other reactions that have been observed with dihydrocodeine or other opioids include respiratory depression, orthostatic hypotension, cough suppression, confusion, diarrhea, miosis, abdominal pain, dry mouth, indigestion, anorexia, spasm of biliary tract, and urinary retention. Physical and psychological dependence are possibilities. Hypersensitivity reactions (including anaphylactoid reactions), hallucinations, vivid dreams, granulomatous interstitial nephritis, severe narcosis and acute renal failure have been reported rarely during dihydrocodeine administration.
Acetaminophen in therapeutic doses rarely causes adverse reactions. The most serious adverse reaction is hepatotoxicity from overdosage (see OVERDOSAGE). Thrombocytopenia, leukopenia, pancytopenia, neutropenia, thrombocytopenic purpura, and agranulocytosis have been reported in patients receiving acetaminophen or ρ-aminophenol derivatives. Hypersensitivity reactions including urticarial or erythematous skin reactions, laryngeal edema, angioedema, or anaphylactoid reactions are rare.
Adverse reactions associated with caffeine use include anxiety, anxiety neurosis, excitement, headaches, insomnia, irritability, lightheadedness, restlessness, tenseness, tremor, extrasystoles, palpitations, tachycardia, diarrhea, nausea, stomach pain, vomiting, diuresis, urticaria, scintillating scotoma, and tinnitus.