Pharmacokinetics of indoprofen in elderly patients following repeated oral administration

Twenty patients suffering from osteoarthritis or rheumatoid arthritis, aged between 60 and 85 years, received 200 mg indoprofen tablets thrice daily for 4-7 days. Following the last dose, plasma samples were drawn and analysed for indoprofen. The mean peak plasma concentration of 25.5 +/- 7.06 micrograms/ml indoprofen was reached after 1.25 +/- 0.71 h. The total area under the curve was calculated as 207.2 +/- 108.7 micrograms X h/ml. Indoprofen was eliminated with a mean elimination half-life of t1/2 beta = 8.29 +/- 2.93 h compared with 5.5 +/- 0.64 h in young subjects. In elderly patients receiving indoprofen, terminal plasma half-lives and area under the plasma level time curves corrected for body weight were moderately increased compared with young subjects whereas no significant differences were found for Vd beta. During the dosage interval indoprofen levels were appreciably higher in elderly patients than in healthy volunteers due to higher nadir values and slower elimination half-lives, whereas only minor differences could be detected for peak plasma levels. The differences observed between young healthy volunteers and elderly patients may be explained by the reduction of renal function with increasing age, since creatinine clearance was 30-40% lower than normal values. The dose schedule for elderly patients over 60 years of age should therefore be adjusted to 200 mg indoprofen twice daily. A further reduction of the total daily dose should be considered for patients suffering from renal diseases associated with reduced creatinine clearance.