Sensitive gas chromatographic method for the determination of cinnarizine and flunarizine in biological samples

A sensitive method has been developed for the determination of the vasoactive compounds cinnarizine and flunarizine in plasma, urine and milk samples from man and animals. The procedure involves the extraction of the drugs and their internal standard from the biological samples at alkaline pH, back-extraction into sulphuric acid and re-extraction into the organic phase (heptane-isoamyl alcohol). The analyses were carried out by gas chromatography using a nitrogen-selective thermionic specific detector. The detection limit was 0.5 ng/ml of biological fluid and extraction recoveries were sufficiently high (87-94%). The method was applied to plasma samples from bioavailability studies of both cinnarizine and flunarizine in healthy volunteers, and to plasma, urine and milk samples from flunarizine-treated dogs.