Gbotosho Grace O, Happi Christian T, Sijuade Abayomi O, Sowunmi Akin, Oduola Ayoade M J
Department of Pharmacology and Therapeutics, College of Medicine, University of Ibadan, Ibadan, Nigeria.
Malar J. 2009 Oct 24;8:238. doi: 10.1186/1475-2875-8-238.
Artesunate plus sulphadoxine-pyrimethamine is one of the four artemisinin-based combination therapies currently recommended by WHO as first-line treatment for falciparum malaria. Sulphadoxine-pyrimethamine is also used for intermittent preventive treatment for malaria in pregnancy. Drug use patterns and drug pharmacokinetics are important factors impacting the spread of drug resistant parasites hence it is imperative to monitor the effect of pharmacokinetic variability on therapeutic efficacy. Unfortunately, information on the pharmacokinetics of sulphadoxine in children and pregnant women with malaria is very limited. Methods for the assay of sulphadoxine-pyrimethamine have been previously reported, but they are not cost-effective and practicable in analytical laboratories in low resource areas where malaria is endemic. Efforts in this study were thus devoted to development and evaluation of a simple, cost-effective and sensitive method for quantification of sulphadoxine in small capillary samples of whole blood dried on filter paper.
Sulphadoxine was determined in whole blood by reversed-phase high performance liquid chromatography with UV detection at 340 nm. Sulisoxazole (SLX) was used as internal standard. Chromatographic separation was achieved using a Beckman Coulter ODS C18 and a mobile phase consisting of 0.05 M phosphate buffer-methanol-acetonitrile (70:17:13 V/V/V) containing 1% triethylamine solution.
Standard curves from sulphadoxine-spiked blood added to filter paper were linear over the concentration range studied. Linear regression analysis yielded correlation coefficient r2>0.99 (n=6). Extraction recoveries were about 82-85%. The limit of quantification was 120 ng/ml while the within and between assay coefficient of variations were <10%. The inter-day precision was <5.8% and inter-day accuracy ranged from 4.1 to 5.3%. There was no interference from endogenous compounds or any of the commonly used anti-malarial, analgesic and anti-infective drugs with the peaks of SDX or the internal standard.
The recovery and accuracy of determination of SDX from whole blood filter paper samples using the method described in this study is satisfactory, thus making the method a valuable tool in epidemiological studies and therapeutic drug monitoring in developing endemic countries. Furthermore, the applicability of the method in studying the pharmacokinetic disposition of SDX in a patient suggests that the method is suitable in malaria endemic areas.
青蒿琥酯加磺胺多辛-乙胺嘧啶是世界卫生组织目前推荐的四种以青蒿素为基础的联合疗法之一，用于治疗恶性疟原虫疟疾的一线治疗。磺胺多辛-乙胺嘧啶还用于孕期疟疾的间歇性预防治疗。药物使用模式和药物药代动力学是影响耐药寄生虫传播的重要因素，因此监测药代动力学变异性对治疗效果的影响至关重要。不幸的是，关于疟疾患儿和孕妇中磺胺多辛药代动力学的信息非常有限。此前已有磺胺多辛-乙胺嘧啶的检测方法报道，但在疟疾流行的资源匮乏地区的分析实验室中，这些方法既不具成本效益也不可行。因此，本研究致力于开发和评估一种简单、经济高效且灵敏的方法，用于定量滤纸干燥全血小毛细管样本中的磺胺多辛。
采用反相高效液相色谱法，在340nm处进行紫外检测，测定全血中的磺胺多辛。磺胺异恶唑（SLX）用作内标。使用贝克曼库尔特ODS C18色谱柱和由含1%三乙胺溶液的0.05M磷酸盐缓冲液-甲醇-乙腈（70:17:13 V/V/V）组成的流动相实现色谱分离。
添加到滤纸上的加标磺胺多辛血液的标准曲线在所研究的浓度范围内呈线性。线性回归分析得到相关系数r2>0.99（n = 6）。提取回收率约为82 - 85%。定量限为120 ng/ml，批内和批间变异系数<10%。日间精密度<5.8%，日间准确度范围为4.1%至5.3%。内源性化合物或任何常用的抗疟药、镇痛药和抗感染药对SDX峰或内标均无干扰。
使用本研究中所述方法从全血滤纸样本中测定SDX的回收率和准确度令人满意，因此该方法成为发展中流行国家流行病学研究和治疗药物监测的宝贵工具。此外，该方法在研究患者中SDX的药代动力学处置方面的适用性表明该方法适用于疟疾流行地区。
