Bioavailability of diclofenac potassium at low doses

• Published in: British journal of clinical pharmacology Vol. 59; no. 1; pp. 80 - 84
• Main Authors: Hinz, Burkhard, Chevts, Julia, Renner, Bertold, Wuttke, Henrike, Rau, Thomas, Schmidt, Andreas, Szelenyi, Istvan, Brune, Kay, Werner, Ulrike
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.01.2005; Blackwell Science; Blackwell Science Inc
• Subjects: Adult; Anti-Inflammatory Agents, Non-Steroidal - administration & dosage; Anti-Inflammatory Agents, Non-Steroidal - pharmacokinetics; Area Under Curve; bioavailability; Biological and medical sciences; Biological Availability; Chromatography, High Pressure Liquid; Cross-Over Studies; Cyclooxygenase Inhibitors - administration & dosage; Cyclooxygenase Inhibitors - pharmacokinetics; diclofenac; Diclofenac - administration & dosage; Diclofenac - pharmacokinetics; Drug Distribution; Female; Humans; Male; Medical sciences; pharmacokinetics; Pharmacology. Drug treatments; potassium salt; Prostaglandin-endoperoxide synthase; Enzyme; Low dose; potassium salt; Enzyme inhibitor; Bioavailability; Inorganic element; Diclofenac; Non steroidal antiinflammatory agent; Salt; Arylacetic acid derivatives; Analgesic; Antipyretic; Oxidoreductases; Pharmacokinetics; Potassium
• ISSN: 0306-5251; 1365-2125
• DOI: 10.1111/j.1365-2125.2005.02226.x

Aim Diclofenac‐K has been recently launched at low oral doses in different countries for over‐the‐counter use. However, given the considerable first‐pass metabolism of diclofenac, the degree of absorption of diclofenac‐K at low doses remained to be determined. The aim of this study was to determine the bioavailability of low‐dose diclofenac‐K. Methods A randomized, three‐way, cross‐over study was performed in 10 subjects. Each received diclofenac‐K, 22.5 mg via short‐term i.v. infusion and orally at single doses of 12.5 mg and 25 mg. Results Mean (± SD) times to maximal plasma concentration (tmax) of diclofenac were 0.48 ± 0.28 h (12.5 mg) and 0.93 ± 0.96 h (25 mg). The absolute bioavailability of diclofenac‐K after oral administration did not differ significantly in the 12.5‐mg and 25‐mg dose group (63.1 ± 12.6%vs. 65.1 ± 19.4%, respectively). The 90% confidence intervals for the AUC∞ and AUCt ratios for the two oral regimes were 82.6, 103.4% (point estimate 92.4%) and 86.2, 112.9% (point estimate 98.6%), respectively. These values were within the acceptance criteria for bioequivalence (80–125%). Conclusions Our data indicate that diclofenac‐K is rapidly and well absorbed at low dose, and are consistent with a rapid onset of action of the drug. Abbreviations AUC, area under plasma concentraton‐time curve; Cmax, peak plasma concentration; CI, confidence interval; COX, cyclooxygenase; D, dose; F, absolute bioavailability; tmax, time to reach Cmax.