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.

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.

Unexplained acute severe methaemoglobinaemia in a young adult.

This report describes the case of an otherwise healthy young adult female, who presented with a 12-h history of progressive bluish discolouration of lips and limbs. She denied ingesting or inhaling any drug or substance. A high PaO2 in the presence of 'cyanosis' and 'dark blood' led to suspicion of methaemoglobinaemia. Co-oximetry revealed the methaemoglobin level to be 47%. A urinary screen for drugs of abuse was negative and blood methaemoglobin reductase activity was within the normal range. The aetiology was traced to dapsone detected in the urine by gas chromatography/mass spectrometry. The therapeutic and diagnostic approach in such patients is discussed.

Neither dapsone hydroxylation nor cortisol 6beta-hydroxylation detects the inhibition of CYP3A4 by HIV-1 protease inhibitors.

OBJECTIVE: This study examined the use of dapsone N-hydroxylation and cortisol 6beta-hydroxylation, well accepted in vivo probes of cytochrome P4503A4 (CYP3A4) activity, on defining the effect of three HIV protease inhibitors on CYP3A4 activity. METHODS: Subjects from University Hospital Infectious Disease Clinic about to be started on indinavir, and subjects from two clinical studies, one using ritonavir and the other using amprenavir, were recruited to participate in the study. Subjects received dapsone 100 mg p.o. followed by an 8-h urine collection for dapsone, dapsone N-hydroxylamine, cortisol, and 6beta-hydroxycortisol concentrations before HIV protease inhibitor administration, and 3 4 weeks into receiving HIV protease inhibitors. RESULTS: None of the HIV protease inhibitors demonstrated statistically significant alterations in dapsone recovery ratio and 6beta-hydroxycortisol/cortisol ratio. In fact, with ritonavir, the dapsone recovery ratio tended to increase rather than decrease, suggesting induction. These negative results were found despite evidence of CYP3A4 inhibition by these three HIV protease inhibitors via published drug-drug interactions with drugs that are substrates for CYP3A4. CONCLUSIONS: These in vivo assays used to probe CYP3A4 activity are suboptimal, most likely because of the presence of extrahepatic sites of metabolism for both dapsone and cortisol, and multiple CYP isozymes involved in dapsone N-hydroxylation.

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.

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.

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.

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.

Multidrug therapy in multibacillary leprosy; experience in an urban leprosy center.

The article records the experience of treating multibacillary (BB, BL and LL) leprosy with multidrug therapy (MDT) in an urban leprosy center. The problem of leprosy is to be properly assessed throughout the Indian subcontinent because most of the epidemiological data from the areas labeled low-endemic have to be updated. The regularity of therapy must be ensured and monitored constantly, but in spite of our efforts to do so some factors were beyond our control, such as providing a means of livelihood for the migrants from other places. In addition, the intake of drugs also has to be periodically checked from the history and discoloration of skin and, most importantly, confirmed by performing random spot tests for dapsone in the urine. The main problems discussed are the difficulty in demonstrating acid-fast bacilli in slit-skin smears from the macular form of borderline leprosy (also called dimorphous macular) and, secondly, whether the duration of multibacillary therapy was adequate since only approximately 50% of our patients achieved smear negativity after taking MDT for the stipulated period of 24 months. Experiences from other centers have suggested that the duration of MDT should be prolonged in multibacillary patients to achieve smear-negative status. Yet another group notes that smear negativity is gradually achieved during the period of surveillance following stoppage of MDT after 24 months. These questions await more information from good centers with controlled field studies.

Simultaneous high performance liquid chromatographic determination of dapsone and monoacetyldapsone in human plasma and urine.

A rapid, specific and a one-stage protein precipitation method for simultaneous estimation of dapsone (DDS) and monoacetyldapsone (MAD) concentration in plasma and urine using high performance liquid chromatography (HPLC) is described. The applicability of the method for monitoring DDS and MAD blood levels in two different acetylator phenotype volunteers following the administration of 100-mg oral dose of DDS was shown. Cumulative urinary excretion of DDS and MAD were studied in the same volunteers.

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.

Compliance with malaria chemoprophylaxis over a five-year period among children in a rural area of The Gambia.

We have reviewed a malaria chemoprophylaxis programme in which Maloprim (pyrimethamine and dapsone) has been administered fortnightly by village health workers (VHWs) to approximately 1500 children each year aged 6-59 months resident in 15 primary health care villages in a rural area of The Gambia over 5 years. Reasonable levels of compliance with chemoprophylaxis have been maintained by many children over this period. this has occurred despite minimal outside supervision and support of the programme. Factors which may have affected the level of compliance in individual villages are identified. Large villages and those where social or political factionalism were evident tended to have low levels of compliance. The attitudes of VHWs and mothers to the programme were determined. Most VHWs cooperated enthusiastically and kept accurate records of compliance, despite receiving no compensation from the villagers for administering chemoprophylaxis. The administration of a drug to prevent illness in children was complementary to the curative service provided by VHWs. The chemoprophylactic was widely acceptable and nearly all mothers stated that the tablets were good for their children's health. However, knowledge of the specific purpose of chemoprophylaxis in the prevention of malaria was limited. Improvements in the programme which may result in higher levels of compliance are discussed.

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.

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.

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.

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.

Instrumental variables in the evaluation of diagnostic test procedures when the true disease state is unknown.

We explore the estimation of sensitivity and specificity of diagnostic tests when the true disease state is unknown. Instrumental variables which subdivide the patient population are used. A logistic model, relating these instrumental variables to the (unknown) true disease state is proposed. It is shown that this procedure allows the goodness-of-fit to the resulting model to be tested.