Flow injection chemiluminescence sensor using core-shell molecularly imprinted polymers as recognition element for determination of dapsone.

This paper reports the preparation of dapsone (DDS) imprinted polymer layer-coated silica submicron particles (SiO(2)) combined with chemiluminescence (CL) toward analysis of tracing DDS in practical samples. To induce the selective occurrence of surface polymerization, the amino groups were first grafted at the surface of SiO(2) by the (3-aminopropyl)triethoxysilane (APTES). The molecularly imprinted polymers (MIP) were coated at the surface of modified SiO(2) by the graft copolymerization. After the removal of templates, recognition sites of DDS were exposed in the polymer layers. The DDS-imprinted products were characterized by FT-IR, SEM, TEM, dynamic adsorption, and static adsorption tests. The proximity between the thickness of MIP layer and the spatial size of DDS indicated that the imprinted sites almost situated at the surface of MIP, leading to rapid adsorption saturation within 90 min. The apparent maximum binding amount of MIP toward DDS was evaluated as 14.98 mg·g(-1), which was much higher than that of non-molecularly imprinted polymers. The CL sensor provided a wide linear range for DDS within 1.0 × 10(-6) to 1.0 × 10(-4) mol·L(-1) with a detection limit of 5.27 × 10(-7) mol·L(-1) and the relative standard deviation of 1.8 % (n = 11) by determinations of 5.0 × 10(-6) mol·L(-1) DDS. This method was applied to determine DDS in urine samples and satisfactory results were obtained.

Absence of correlations among three putative in vivo probes of human cytochrome P4503A activity in young healthy men.

In vitro studies with human liver microsomes have shown that erythromycin N-demethylation, dapsone N-hydroxylation, and the 6 beta-hydroxylation of cortisol are all primarily mediated by P4503A4. Trait measurements to assess the in vivo level of activity of these separate oxidations have also been developed previously. This study investigated the relationships among the three phenotypic trait measurements in 30 young healthy white men. The frequency distributions of the trait values were all unimodal, with a twofold range for the erythromycin breath test and the urinary dapsone recovery ratio; the urinary 6 beta-hydroxycortisol/cortisol ratio was more variable, with a 17-fold range of values. No statistically significant correlations were observed among any of the trait measurements (dapsone recovery ratio versus erythromycin breath test: r = -0.07, p = 0.7; urinary 6 beta-hydroxycortisol/cortisol ratio versus erythromycin breath test: r = -0.12, p = 0.6; urinary 6 beta-hydroxycortisol/cortisol ratio versus dapsone recovery ratio: r = 0.13, p = 0.5. This lack of any relationship was unexpected and the reason(s) is unknown; however, it is possible that factors such as route of administration and extrahepatic metabolism in the intestinal epithelium and kidney are involved. Further studies are required to identify and validate the use of an appropriate in vivo probe of P4503A4 in humans.

Differences between white subjects and Chinese subjects in the in vivo inhibition of cytochrome P450s 2C19, 2D6, and 3A by omeprazole.

OBJECTIVES: To determine the effects of omeprazole on indexes of CYP2D6, CYP2C19 and 3A in vivo activity and to compare these in white subjects and Chinese subjects. METHODS: Omeprazole, 40 mg/day, or placebo were administered in a double-blind crossover study for 3 weeks to eight healthy white and seven Chinese male extensive metabolizers of mephenytoin and debrisoquin. Debrisoquin (10 mg), dapsone (100 mg), and mephenytoin (100 mg) were given 1 week before administration, on the last day of administration, and 3 weeks after administration, and urine was collected over 8 hours. Phenotypic trait values were obtained from the urinary recoveries of the probe drugs or their metabolites. RESULTS: In the white subjects, omeprazole significantly inhibited CYP2C19-mediated S-mephenytoin metabolism as indicated by decreases in the urinary R/S enantiomeric ratio (63% +/- 13%; p < 0.02; mean +/- SD) and the excretion of 4'-hydroxymephenytoin (39% +/- 13%; p < 0.001). Similar but smaller changes were also noted in Chinese subjects, 22% +/- 25% (p = 0.08) and 29% +/- 13% (p < 0.002), respectively. The interracial differences in the extent of inhibition of metabolism were statistically significant (p < 0.01 and p < 0.05, respectively). In contrast, the debrisoquin urinary metabolic ratio, a measure of CYP2D6, was unaffected. The excretion of hydroxylamine dapsone-a putative probe of CYP3A activity-was reduced by 40% +/- 30% (p < 0.03) in white subjects but not in Chinese subjects. CONCLUSIONS: Omeprazole selectively inhibits the in vivo metabolism of S-mephenytoin, consistent with the predictions based on in vitro studies. The extent of interaction is greater in subjects of white European ancestry. It is to be expected that similar situations would also occur when omeprazole is coadministered with other substrates of CYP2C19.

Compliance with malaria chemoprophylaxis programmes in Zimbabwe.

Compliance with malaria chemoprophylaxis programmes was studied in the National Railways and two large commercial farm labour forces in Zimbabwe. Prophylaxis was primarily conducted using pyrimethamine/dapsone and the study measured compliance rates through interview and the detection of drug in the urine. Compliance rates as indicated from registers or questioning were not always reliable and were found from urine examination to be in the range of 50-60% for the farm labour force. Annual drug utilization figures also indicated that complete coverage was not being achieved. - The results are discussed in relation to the difficulties involved in implementing malaria prophylaxis programmes. The limited use of large scale chemoprophylaxis is stressed, particularly in the light of increasing drug resistance.

Electroanalysis of dapsone, an anti-leprotic drug.

The electrochemical oxidation and adsorption of dapsone, an anti-leprotic drug were studied in aqueous alcohol medium at a stationary glassy carbon electrode. Cyclic voltammetry studies showed one well-defined oxidation peak in the potential range 1.2-1.9 V at pH conditions 1.0, 4.0, 7.0, 9.2 and 13.0. The oxidation was irreversible and exhibited diffusion controlled adsorption. Controlled potential coulometry revealed one electron oxidation of the amino group in the molecule. A systematic study of the experimental parameters that affect the squarewave stripping response was carried out and the optimized experimental conditions were arrived at. A calibration plot was derived for the determination of the compound in solution. This method was used for the determination of dapsone in tablets and urine. The limits of determination was 0.0036 and 3.56 mg/ml and the relative standard deviation (n=10) was 4 ppt (0.4%) at a concentration level 0.100 mg/ml.

Self-administered drug compliance in Nepali leprosy patients.

The self administration of dapsone by Nepali leprosy patients receiving multidrug therapy was assessed by a colorimetric and a filter paper spot test. Overall 45 out of 337 (13.3%) patients were found to be non-compliant. The relation of non-compliance to sex, age, leprosy classification, therapy type and length of therapy was investigated. The spot test was compared with the colorimetric assay and found to have a relative sensitivity of 99.3% and specificity of 95.4%. Follow up of patients was successful in that two-thirds of non-compliant patients were compliant on their follow-up test.

Life after multidrug therapy: the managerial implications in leprosy control in Kaduna State, Nigeria.

Multidrug therapy (MDT) represents a most effective technology for the chemotherapy of leprosy. This has created a belief that elimination of leprosy through MDT is a possibility. However, the managerial implications of MDT are not always appreciated. This study highlights major managerial implications of MDT implementation using the Kaduna State Leprosy Control (Nigeria) as a focal point.

A comparative study of the haemagglutination inhibition (HI) test and spot test for detection of dapsone in urine.

A comparative study of the HI test and paper spot test for screening dapsone in urine was carried out in 692 specimens of urine, 149 from the field and 502 from patients attending the C.L.T. and R.I. clinic or admitted in the wards and 41 control urines. A very good correlation was noticed between the 2 tests in relation to positivity or negativity as well as DDS concentration. Fifty one urine specimens showed a specific agglutination, 41 of them were considered HI positive and 10 of them HI negative based on DDS concentration. The results are discussed.

Application of HI test for dapsone in urine under field conditions.

One hundred and two specimens of urine collected from leprosy patients attending the field clinics of Central Leprosy Teaching and Research Institute, Chingleput, Tamil Nadu, India, were screened for dapsone by the paper spot test and Haemagglutination Inhibition (HI) tests. A concordance of about 90% was observed between the two tests. Both tests showed their merits. The lower sensitivity of the spot test finds more cases of irregular compliance (1-2 days), whereas the higher sensitivity of the HI allows the demonstration of the intake of lower doses and the detection of those cases, who have grossly missed their tablets (longer than a week).

Dapsone drug compliance study among leprosy patients: a comparison between qualitative and quantitative methods.

The methods currently employed to monitor self-administration of dapsone have been evaluated by comparing the results of the qualitative spot test and quantitative DDS/creatinine ratio test. Random urine samples of 242 leprosy patients, periodically attending the Leprosy Clinic were tested. Although a good correlation between the results of the two tests was evident, the DDS/creatinine ratio technique appeared to be more sensitive than the spot test. The concentration of DDS and its metabolites in urine specimens found to be negative by the spot test, ranged from 3.32-12.37 micrograms of DDS/mg creatinine. The spot test was found to be more specific and stays to be the method of choice, when rapidity and reproducibility are the prime objectives, and sensitivity can be marginally compromised. Acidification of urine prior to the spot test was found to be desirable to rule out false negative and false positive reactions.

Comparison of a urine spot test and blood tests as indicators of patient compliance.

Irregular drug intake has been a concern of leprosy control programmes for many years and various methods have been used to monitor and encourage patient compliance. This study compares the results of a urine spot test for dapsone as proposed by Huikeshoven, with blood levels measured in the same patients by the modified Bratton Marshall method and by high performance liquid chromatography. Two hundred-sixty urine and blood specimens were obtained from subjects who were taking supervised and unsupervised medications as well as from controls who were taking no medications. The results indicate that the urine spot test is simple and easily performed, and for monitoring patient compliance under routine clinical conditions (hospital or field work) it compares favourably with blood levels of dapsone estimated by the Bratton Marshall method or by high performance liquid chromatography. The study also shows that dapsone level is not a good indicator of compliance in patients who are also taking daily rifampicin but the urine spot test remains useful in such patients.

Drug compliance among self-motivated leprosy patients.

Regularity of DDS intake among 366 leprosy patients attending our out patient department voluntarily was assessed by urine spot test. It was found that only 54.6% of them had taken their last dose of drug within the previous three days. Those who kept their appointment showed better compliance than those who did not. Urinary DDS positivity was found to be unrelated to sex, occupation or the type of the disease. In the younger age group the compliance was low, as also among the patients coming from nearby places as compared to those who were residing in far off districts.

Pattern of drug compliance in leprosy patients attending urban centres--a longitudinal study.

The pattern of drug compliance in 485 leprosy patients attending urban leprosy centres in Bombay was studied for 2 years. The study subjects included 113 patients with paucibacillary leprosy under dapsone monotherapy, 241 patients with paucibacillary leprosy under multidrug therapy and 131 patients with multibacillary leprosy under multidrug therapy. Their urine samples had been checked at least 6 times during the 2 years by DDS tile test at the time of their clinic attendance. The urine test results were not disclosed to the patients, but patients showing negative results were counselled about the need for regular drug intake. 35% of the patients were "Regular through out", 13% were "Irregular through out" and the other 52% who "Tended to be irregular" in their drug intake became "Regular" after counselling. Regularity in drug compliance was better in patients on multidrug therapy than in those on monotherapy. It is suggested that periodic testing of urine for checking for regularity of drug intake and subsequent counselling of patients should be made a routine practice to maintain drug compliance at a high level.

Treatment compliance by leprosy out-patients and its monitoring under field condition.

The widely experienced poor treatment compliance by leprosy out-patients has interfered with effective leprosy control and contributed to the problem of drug (dapsone) resistance. This paper summarises (1) the pattern of treatment compliance by rural and urban patients in a leprosy hyperendemic area, and (2) various methods to monitor the treatment compliance, especially under field conditions. Two simple methods of monitoring the dapsone intake by patients viz. "Physical verification of DDS tablets with patients" and "paper spot test", when applied together, by a field worker in the field, were found to be operationally very feasible, economical and acceptable; and had good correlation with each other. Thus these methods are recommended to be used on large scale in leprosy control programme. The paper spot test was found to be 98% reliable, when compared with DDS/Cr. ratio estimation. In addition, communities and patients be continuously educated about leprosy and its control; and for the optimal utilization of medical care services by patients, they should be organized in background of the consumers.

Comparative value of Dapsone "spot test" and Dapsone "tile test" in leprosy control programme.

The sensitivity of Dapsone "spot test" with modified Ehrlich's reagent (Balakrishnan, 1968) and Dapsone "tile test" using Barton-Marshall reagents (Irudayraj, 1981)--both being qualitative tests for screening of dapsone in urine are compared with Dapsone/creatinine ratio--a quantitative test (Ellard, 1974). 316 urine samples were processed by paramedical worker in the fields for Dapsone "Tile test" and Dapsone "Spot test". The same samples were brought to the laboratory and subjected to these two tests besides Dapsone/creatinine estimation. These three tests correlated well at the level of 91%. The results obtained by paramedical workers and experienced worker at the laboratory are also showed 97% concordance. An earlier investigations revealed that monitoring through frequent and surprise check-up of urines for drug content (4-5 samples/year/patient) and subsequent motivation and persuation of leprosy patient, the irregularity rate of drug consumption by patient could be brought down from 36% to 17% in one year. The kit for performing DDS "spot test" and DDS "tile test" being light and easy to carry in the field and the tests being simple to perform with reliable results. This procedure is recommended to be applied in the field on a mass scale. The routine frequent and surprise checking of urine for drug content will give early idea about irregularity status of drug consumption by patients as compared to the judgement relying on clinical assessment and reduction of bacteriological index of infectious patients.

Improving patient compliance--a multicentre evaluation of the 'DDS tile test'.

The feasibility and utility of the "DDS tile test" under field conditions was assessed in 112 leprosy centres in Maharashtra. About 10% of the 2952 urine samples tested negative for dapsone. Feed back information from 54 centres one year later showed that the test could be performed easily under field conditions and also that counselling of patients showing poor compliance helped to improve drug compliance in over 80% of cases.