Simultaneous liquid chromatographic analysis of ritonavir, quinine and 3-hydroxyquinine in human plasma

A Novel Equipment-Free Paper-Based Fluorometric Method for the Analytical Determination of Quinine in Soft Drink Samples

A simple, equipment-free, direct fluorometric method, employing paper-based analytical devices (PADs) as sensors, for the selective determination of quinine (QN) is described herein. The suggested analytical method exploits the fluorescence emission of QN without any chemical reaction after the appropriate pH adjustment with nitric acid, at room temperature, on the surface of a paper device with the application of a UV lamp at 365 nm. The devices crafted had a low cost and were manufactured with chromatographic paper and wax barriers, and the analytical protocol followed was extremely easy for the analyst and required no laboratory instrumentation. According to the methodology, the user must place the sample on the detection area of the paper and read with a smartphone the fluorescence emitted by the QN molecules. Many chemical parameters were optimized, and a study of interfering ions present in soft drink samples was carried out. Additionally, the chemical stability of these paper devices was considered in various maintenance conditions with good results. The detection limit calculated as 3.3 S/N was 3.6 mg L^-1, and the precision of the method was satisfactory, being from 3.1% (intra-day) to 8.8% (inter-day). Soft drink samples were successfully analyzed and compared with a fluorescence method.

Alteration of the Disposition of Quinine in Healthy Volunteers After Concurrent Ciprofloxacin Administration

This study evaluated the effects of concurrent ciprofloxacin administration on the disposition of quinine in healthy volunteers. Quinine (600-mg single dose) was administered either alone or with the 11th dose of ciprofloxacin (500 mg every 12 hours for 7 days) to 15 healthy volunteers in a crossover fashion. Blood samples collected at predetermined time intervals were analyzed for quinine and its major metabolite, 3-hydroxquinine, using a validated high-performance liquid chromatographic method. Administration of quinine plus ciprofloxacin resulted in significant increases (P < 0.05) in the total area under the concentration-time curve, maximum plasma concentration (Cmax), and terminal elimination half-life (T1/2b) of quinine compared with values with quinine dosing alone (AUC: 27.93 ± 8.04 vs. 41.62 ± 13.98 h·mg/L; Cmax: 1.37 ± 0.24 vs. 1.64 ± 0.38 mg/L; T1/2b: 16.28 ± 2.66 vs. 21.43 ± 3.22 hours), whereas the oral plasma clearance markedly decreased (23.17 ± 6.49 vs. 16.00 ± 5.27 L/h). In the presence of ciprofloxacin, there was a pronounced decrease in the ratio of AUC (metabolite)/AUC (unchanged drug) and highly significant decreases in Cmax and AUC of the metabolite (P < 0.05). Ciprofloxacin may increase the adverse effects of concomitantly administered quinine, which can have serious consequences on the patient. Thus, a downward dosage adjustment of quinine seems to be necessary when concurrently administered with ciprofloxacin.

Analysis of alkaloids from different chemical groups by different liquid chromatography methods

Alkaloids are biologically active compounds widely used as pharmaceuticals and synthesised as secondary methabolites in plants. Many of these compounds are strongly toxic. Therefore, they are often subject of scientific interests and analysis. Since alkaloids — basic compounds appear in aqueous solutions as ionized and unionized forms, they are difficult for chromatographic separation for peak tailing, poor systems efficiency, poor separation and poor column-to-column reproducibility. For this reason it is necessity searching of more suitable chromatographic systems for analysis of the compounds. In this article we present an overview on the separation of selected alkaloids from different chemical groups by liquid chromatography thus indicating the range of useful methods now available for alkaloid analysis. Different selectivity, system efficiency and peaks shape may be achieved in different LC methods separations by use of alternative stationary phases: silica, alumina, chemically bonded stationary phases, cation exchange phases, or by varying nonaqueous or aqueous mobile phase (containing different modifier, different buffers at different pH, ion-pairing or silanol blocker reagents). Developments in TLC (NP and RP systems), HPLC (NP, RP, HILIC, ion-exchange) are presented and the advantages of each method for alkaloids analysis are discussed.

Pharmacokinetic interactions between ritonavir and quinine in healthy volunteers following concurrent administration

AIMS

To evaluate the pharmacokinetic interactions between ritonavir and quinine in healthy volunteers.

METHODS

Ten healthy volunteers were each given 600-mg single oral doses of quinine alone, ritonavir alone (200 mg every 12 h for 9 days), and quinine in combination with ritonavir, in a three-period pharmacokinetic nonrandomized sequential design study. Quinine was co-administered with the 15th dose of ritonavir. Blood samples collected at predetermined time intervals were analysed for ritonavir, quinine and its major metabolite, 3-hydroxyquinine, using a validated high-performance liquid chromatography method.

RESULTS

Concurrent ritonavir administration resulted in about fourfold increases in both the C(max) and AUC(T)[C(max) 2.79 +/- 0.22 vs. 10.72 +/- 0.32 mg l(-1), 95% confidence interval (CI) 7.81, 8.04; AUC 50.06 +/- 2.52 vs. 220.47 +/- 6.68 mg h(-1) l(-1), 95% CI 166.3, 175.3], a significant increase (P < 0.01) in the elimination half-life (11.15 +/- 0.80 vs. 13.37 +/- 0.33 h, 95% CI 1.64, 2.77) and about a 4.5-fold decrease in CL/F (12.01 +/- 0.61 vs. 2.71 +/- 0.09 l h(-1)) of quinine. Also, with ritonavir, there was a pronounced reduction of AUC(metabolite)/AUC(unchanged drug) ratio of quinine (1.35 +/- 0.10 vs. 0.13 +/- 0.02) along with a marked decrease in C(max) (1.80 +/- 0.12 vs. 0.96 +/- 0.09 mg l(-1)) and AUC(0-48h) (62.80 +/- 6.30 vs. 25.61 +/- 2.44 mg h(-1) l(-1)) of the metabolite. Similarly, quinine caused modest but significant increases (P < 0.01) in the C(max), AUC and elimination T((1/2)) of ritonavir.

CONCLUSIONS

Downward dosage adjustment of quinine appears necessary when concurrently administered with ritonavir.