Drug interactions of the components of Optalidon after oral administration

An investigation involving seven successive was undertaken on several groups of 10 to 14 volunteers, in order to evaluate any drug interaction between the three active components of Optalidon, namely amidopyrine (A), butalbital (B), and caffeine (C). Each component was investigated after oral administration, alone and in combination either with one of the others (i.e. A+B, B+C, C+A) or with both of the others in Optalidon (A+B+C). The plasma concentration and urinary excretion were recorded for each component as a function of time. For amidopyrine, two metabolites, amino-4-antipyrine and acetamino-4-antipyrine, were also measured in the urine. Based on a pharmacokinetic model, the following conclusions can be drawn: a) There is no change in bioavailability due to the combination of the three components in Optalidon in respect to their single administration. Within each study, there is no significant difference between the elimination rate constants, areas under the plasma concentration/time curve and percentage excreted in urine for the three components administered alone or in any combination with the other components of Optalidon. b) Concerning the absorption half-life, there is no change for amidopyrine. Only caffeine and butalbital show a statistically significant interaction in respect to this parameter and, as a consequence, differences in the time and value of the maximal plasma concentration in Optalidon. However, these differences are scarcely of anyl clinical relevance.