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PubMed2001

Crystal structure and mechanism of catalysis of a pyrazinamidase from Pyrococcus horikoshii.

Bacterial pyrazinamidase (PZAase)/nicotinamidase converts pyrazinamide (PZA) to ammonia and pyrazinoic acid, which is active against Mycobacterium tuberculosis. Loss of PZAase activity is the major mechanism of pyrazinamide-resistance by M. tuberculosis. We have determined the crystal structure of the gene product of Pyrococcus horikoshii 999 (PH999), a PZAase, and its complex with zinc ion by X-ray crystallography. The overall fold of PH999 is similar to that of N-carbamoylsarcosine amidohydrolase (CSHase) of Arthrobacter sp. and YcaC of Escherichia coli, a protein with unknown physiological function. The active site of PH999 was identified by structural features that are also present in the active sites of CSHase and YcaC: a triad (D10, K94, and C133) and a cis-peptide (between V128 and A129). Surprisingly, a metal ion-binding site was revealed in the active site and subsequently confirmed by crystal structure of PH999 in complex with Zn(2+). The roles of the triad, cis-peptide, and metal ion in the catalysis are proposed. Because of extensive homology between PH999 and PZAase of M. tuberculosis (37% sequence identity), the structure of PH999 provides a structural basis for understanding PZA-resistance by M. tuberculosis harboring PZAase mutations.

Amidohydrolases↗
PubMed1956

Fate of Mycobacterium tuberculosis in mouse tissues as determined by the microbial enumeration technique. I. The persistence of drug-susceptible tubercle bacilli in the tissues despite prolonged antimicrobial therapy.

Observations are presented on the behavior of populations of tubercle bacilli in the tissues of mice during the administration of antimicrobial drugs. The behavior of the populations during therapy with any particular drug was different depending upon whether the tubercle bacilli were subsisting in the lung or in the spleen. Moreover, the pattern of microbial behavior was distinctive and predictable for each drug studied. Changes in the size of the populations of tubercle bacilli in the tissues appeared to be a more sensitive reflection of drug influence than microscopic study of the number and character of the tuberculous lesions. Nevertheless, in untreated animals, pulmonary lesions evolved and progressed steadily to a fatal outcome despite the fact that the populations of tubercle bacilli had stabilized at a relatively high census early in the course of therapy. The uniform persistence of tubercle bacilli in the spleen throughout prolonged drug administration was demonstrated with every drug or multiple drug regimens except for pyrazinamide when accompanied by isoniazid. Cultures of the bacilli which survived in the tissues despite antimicrobial therapy were highly susceptible to the drugs employed when tested in vitro. Thus the survival of the tubercle bacilli in the tissues represented microbial persistence rather than drug resistance. When pyrazinamide and isoniazid were administered together, it was not possible to detect the microorganisms in the spleen or lungs of treated animals. A detailed investigation of this apparent abolition of microbial persistence forms the subject of an accompanying report.

Aminosalicylic Acid↗
PubMed2005

Serum concentrations of antimycobacterial drugs in patients with pulmonary tuberculosis in Botswana.

BACKGROUND: We conducted a pharmacokinetic study of antimycobacterial drugs involving a cohort of patients with pulmonary tuberculosis (TB) in Gaborone, Botswana, to assess the prevalence of and risk factors for low drug concentrations in serum. METHODS: Adults participated if they had a history of cough > or =2 weeks, had abnormal chest radiograph findings, consented to testing for human immunodeficiency virus (HIV), had sputum cultures positive for Mycobacterium tuberculosis, and were receiving antituberculous therapy for >7 days. Observed maximum serum concentrations were compared with published normal ranges. RESULTS. Of 91 patients enrolled, 89 (98%) were outpatients, and 59 (68%) of 87 patients tested had HIV infection. The following numbers of patients had low serum concentrations of the following drugs: isoniazid, 27 (30%) of 90; rifampin, 71 (78%) of 91; ethambutol, 37 (41%) of 91; and pyrazinamide, 1 (1%) of 91. Low serum concentrations of both isoniazid and rifampin occurred in 23 (26%) of 90 patients. Low serum concentrations of rifampin were found in both HIV-infected and non-HIV-infected patients, and such patients were less likely to have >4 weeks of symptoms, more likely to have lymphadenopathy, and more likely to have low serum albumin levels (P<.05 for all). The associations with noncavitary pulmonary disease (P=.12) and HIV infection (P=.07) did not reach statistical significance. Delayed absorption was most common with ethambutol, followed by rifampin. CONCLUSIONS: These data, predominantly from HIV-infected patients with TB, suggest that low isoniazid, rifampin, and ethambutol concentrations are common in Botswana. In contrast, pyrazinamide usually is well absorbed.

Adult↗
PubMedDate not supplied

Present status of chemotherapy for tuberculosis.

For the treatment of smear-positive pulmonary tuberculosis, short-course chemotherapy of 6 months' duration (with the four-drug combination of isoniazid, rifampin, pyrazinamide, and either ethambutol or streptomycin given daily for a 2-month initial intensive phase followed by a 4-month daily continuation phase with isoniazid and rifampin) is as effective and as acceptable as the standard 9-month daily course of therapy (with isoniazid, rifampin, and ethambutol given for a 2-month initial intensive phase followed by a 7-month daily continuation phase with isoniazid and rifampin). The duration of short-course chemotherapy cannot be further reduced for smear-negative and culture-positive or smear-negative and culture-negative pulmonary tuberculosis or for extrapulmonary tuberculosis. Isoniazid has been demonstrated to be active as prophylactic therapy for tuberculosis at a daily dose of 300 mg (5-10 mg/kg in children) for 6-12 months. Prophylaxis of 2 months' duration with daily administration of isoniazid, rifampin, and pyrazinamide may be as effective as prophylactic therapy with isoniazid of 12 months' duration.

Antitubercular Agents↗
PubMed1996

Randomized controlled trial of a drug regimen that includes ciprofloxacin for the treatment of pulmonary tuberculosis.

The fluoroquinolones are promising new antituberculous agents. A randomized controlled trial of 200 adult patients with sputum smear-positive pulmonary tuberculosis was conducted in Tanzania. Patients received either a trial regimen (HRC) consisting of isoniazid (300 mg), rifampin (600 mg), and ciprofloxacin (750 mg) or a control regimen (HRZE) consisting of isoniazid (300 mg), rifampin (600 mg), pyrazinamide (25 mg/kg), and ethambutol (15 mg/kg). The 168 evaluable patients all had negative smears and cultures by month 6, but the time to conversion to negativity was longer for the HRC group than for the HRZE group because of the poor response of patients infected with human immunodeficiency virus (HIV) to the HRC regimen. Relapse was more frequent in the HRC group. The sterilizing activity of ciprofloxacin does not appear to be equal to that of the combination of pyrazinamide and ethambutol, but the difference in outcome was significant only among HIV-infected patients.

AIDS-Related Opportunistic Infections↗
PubMed2003

Alginate-based oral drug delivery system for tuberculosis: pharmacokinetics and therapeutic effects.

Alginate microparticles were developed as oral sustained delivery carriers for antitubercular drugs in order to improve patient compliance. In the present study, pharmacokinetics and therapeutic effects of alginate microparticle encapsulated antitubercular drugs, i.e. isoniazid, rifampicin and pyrazinamide were examined in guinea pigs. Alginate microparticles containing antitubercular drugs were evaluated for in vitro and in vivo release profiles. These microparticles exhibited sustained release of isoniazid, rifampicin and pyrazinamide for 3-5 days in plasma and up to 9 days in organs. Peak plasma concentration (Cmax), Tmax, elimination half-life (t1/2e) and AUC0- infinity of alginate drugs were significantly higher than those of free drugs. The encapsulation of drug in alginate microparticles resulted in up to a nine-fold increase in relative bioavailability compared with free drugs. Chemotherapeutic efficacy of alginate drug microspheres against experimental tuberculosis showed no detectable cfu values at 1:100 and 1:1000 dilutions of spleen and lung homogenates. Histopathological studies further substantiated these observations, thus suggesting that application of alginate-encapsulated drugs could be useful in the effective treatment of tuberculosis.

Administration, Oral↗
PubMed1998

Twice weekly tuberculosis preventive therapy in HIV infection in Zambia.

BACKGROUND: A randomized double-blind placebo-controlled trial was conducted to estimate the efficacy of preventive therapy for tuberculosis (TB) in HIV-infected adults in Lusaka, Zambia. The main outcome measures were the incidence of TB, mortality and adverse drug reactions. METHODS: During a 2 year period, 1053 HIV-positive individuals without evidence of clinical TB were randomly assigned to receive 6 months of isoniazid twice a week (H), or 3 months of rifampicin twice a week (R) plus pyrazinamide (Z), or a placebo. Therapy was taken twice a week and was self administered. Subjects presenting with symptoms during the follow-up period were investigated for TB. RESULTS: The 1053 subjects in the study were followed up for a total of 1631 person-years (median = 1.8 years). Twenty-nine subjects were taken off treatment as a result of adverse drug reactions. A total of 96 cases of TB/probable TB (59 TB and 37 probable TB) were diagnosed during the study period and 185 deaths were reported. One hundred and fifteen subjects (11%) did not return to the study clinic at any time after enrolment. The incidence of TB was lower in those subjects on preventive therapy (H and RZ groups combined) compared with those on placebo (rate ratio = 0.60, 95% CI: 0.36-1.01, P = 0.057), as was the incidence of TB/probable TB (rate ratio = 0.60, 95% CI: 0.40-0.89, P = 0.013). The effect of preventive therapy was greater in those with a tuberculin skin test (TST) of 5 mm or greater, in those with a lymphocyte count of 2x10(9)/l or higher, and in those with haemoglobin of 10 g/dl or higher. There was no difference in mortality rates between the preventive therapy and placebo groups. The effect of preventive therapy declined after the first year of the study so that by 18 months the rates of TB in the treated groups were similar to that in the placebo group. CONCLUSION: This study has demonstrated that preventive therapy with either twice weekly isoniazid for 6 months or a combination of rifampicin and pyrazinamide for 3 months reduced the incidence of TB in HIV-infected persons in Zambia. No effect was observed on mortality. The effect was greatest in persons who had a positive TST or a lymphocyte count of 2x10(9)/l or greater, indicating that preventive therapy may be more effective in people with less advanced immunosuppression. The limited duration of the protective effect reported in this study raises the question of the need for lifelong preventive therapy or re-prophylaxis.

AIDS-Related Opportunistic Infections↗
PubMed2001

Duration of efficacy of treatment of latent tuberculosis infection in HIV-infected adults.

BACKGROUND: Treatment of latent infection is needed to protect HIV-infected individuals against tuberculosis. A previous report addressed short-term efficacy of three regimens in HIV-infected adults. We now report on long-term efficacy of the study regimens. METHODS: Three daily self-administered regimens were compared in a randomized placebo-controlled trial in 2736 purified protein derivative (PPD)-positive and anergic HIV-infected adults. PPD-positive subjects were treated with isoniazid (INH) for 6 months (6H), INH plus rifampicin for 3 months (3HR), INH plus rifampicin and pyrazinamide for 3 months (3HRZ), or placebo for 6 months. Anergic subjects were randomized to 6H or placebo. RESULTS: 6H initially protected against tuberculosis in PPD-positive individuals; however, benefit was lost within the first year of treatment. Sustained benefit was observed in persons receiving 3HR and 3HRZ. In a Cox regression analysis, the adjusted relative risk for tuberculosis compared with placebo was 0.67 [95% confidence interval (CI), 0.42-1.07] for 6H, 0.49 (95% CI, 0.29-0.82) for 3HR, and 0.41 (95% CI, 0.22-0.76) for 3HRZ. When the rifampicin-containing regimens were combined, the adjusted relative risk for tuberculosis compared with placebo was 0.46 (95% CI, 0.29-0.71). Among anergic subjects, a modest degree of protection with 6H was present (adjusted relative risk, 0.61; 95% CI, 0.32-1.16). Treatment of latent tuberculosis infection had no effect on mortality. CONCLUSION: Six months of INH provided short-term protection against tuberculosis in PPD-positive HIV-infected adults. Three month regimens including INH plus rifampicin or INH, rifampicin and pyrazinamide provided sustained protection for up to 3 years.

AIDS-Related Opportunistic Infections↗
PubMed1992

Intensive short course chemotherapy for tuberculous meningitis.

This nonrandomized, open clinical investigation of tuberculous meningitis evaluated 53 children with Stage I (n = 8), Stage II (n = 29) and Stage III (n = 16) disease. The overall mortality was 20.8% (11 of 53) with a rate of sequelae of 35.7% (15 of 42) in survivors reflecting the advanced stages of children at diagnosis. Various combinations of standard antituberculous drugs including isoniazid, rifampin, pyrazinamide, streptomycin and ethambutol were given. Three treatment durations used during various time periods were evaluated: 12, 9 and 6 months with only the 6-month regimen receiving pyrazinamide (PZA). This prospective evaluation demonstrated that: (1) severe disease at presentation is highly associated with early mortality (P less than 0.05), regardless of drug regimen; and (2) intensive short course chemotherapy (6 months) with PZA, regardless of stage of disease at presentation, is more efficacious than longer course therapy (9 or 12 months) without PZA in preventing total negative outcomes and sequelae (P less than 0.05). This study demonstrates that a 6-month regimen containing PZA can be used in treating children with tuberculous meningitis.

Antitubercular Agents↗
PubMed2000

Twice weekly vs. daily chemotherapy for childhood tuberculosis.

BACKGROUND: Treating childhood tuberculosis places a large burden on health services, and ways of lessening this were sought. METHODS: A randomized controlled trial was conducted to determine the effectiveness of fully intermittent twice weekly treatment for intrathoracic childhood tuberculosis and its effect on adherence to treatment, in comparison with daily (weekday) treatment. The setting was a district of Cape Town, South Africa, an area of high incident tuberculosis. We randomized 206 children with confirmed (4%), probable (94%) and suspected (2%) intrathoracic tuberculosis: 89 (median age, 25 months) received intermittent treatment; and 117 (median age, 28 months) received daily treatment. Intermittent treatment (twice weekly for 6 months) was isoniazid 15 mg/kg/dose, rifampin 15 mg/kg/dose and pyrazinamide 55 mg/kg/dose for 2 months, followed by isoniazid and rifampin only for 4 months. Daily treatment was isoniazid 10 mg/kg/day, rifampin 10 mg/kg/day and pyrazinamide 25 mg/kg/day on weekdays for 6 months. RESULTS: At 6 months 97% of subjects were discharged, with treatment outcomes in the two groups equivalent at that time (P = 0.90) and at the 18- to 30-month follow-up. One relapse occurred in the twice weekly group (P = 0.25). Adherence was equivalent; 70 children (79%) on intermittent and 90 (77%) on daily treatment took 75% or more of the prescribed doses (P = 0.90). Nonadherence over the full course of therapy was significantly associated with nonadherence during the first month of treatment (P = 0.0002) and household crowding (P = 0.002). CONCLUSIONS: Six month fully intermittent antituberculosis treatment is an effective and acceptable alternative to daily treatment.

Antitubercular Agents↗
PubMed2002

Treatment of childhood tuberculosis with a six month directly observed regimen of only two weeks of daily therapy.

BACKGROUND: Recommended treatment of childhood tuberculosis is 6 months in duration with at least 3 drugs. We studied a regimen requiring as few as 58 doses, given entirely by directly observed therapy (DOT), under program conditions. METHODS: An observational trial was conducted to determine the effectiveness of a completely DOT 6-month regimen for pulmonary, pleural and lymph node tuberculosis in children with the use of 2 weeks of daily isoniazid, rifampin and pyrazinamide therapy; then 6 weeks of twice weekly isoniazid, rifampin and pyrazinamide therapy; followed by 16 weeks of twice weekly isoniazid and rifampin. All therapy was given by workers from the health department, and patients were followed by the Children's Tuberculosis Clinic in Houston, TX. Patients were evaluated for changes in symptoms, weight, clinical or radiographic findings and adherence to therapy. RESULTS: Of the 175 evaluable children (159 pulmonary/thoracic node, 4 pleural, 12 cervical lymph node), 81% of children completed treatment in 6 months. Of the 33 patients who received extended treatment, 3 did so because of physician choice, 17 had an inadequate response to initial therapy, 2 had significant adverse reactions to drugs and 16 had poor adherence to the DOT. Only 37% of patients had complete resolution of disease at the end of treatment, but all continued to improve after therapy was stopped. There was only 1 patient who relapsed after 4 years. CONCLUSION: This regimen had results comparable with those of 6-month regimens with longer durations of daily therapy. Determining treatment response in pediatric tuberculosis is difficult because of the slow resolution of chest radiograph abnormalities. DOT is an important aspect of treatment but does not solve all problems with treatment adherence.

Adolescent↗
PubMed1996

The high incidence of tuberculosis among renal transplant recipients in India.

Tuberculosis is an important infection encountered after renal transplantation in third-world countries. Over an 8-year period, 36 cases of tuberculosis were encountered in 305 renal transplant recipients (11.8%) with grafts functioning for more than 3 months followed up at our center. The infection was limited to the thoracic cavity in 41.7% and a single extrapulmonary site in 11.1%, and it was disseminated in 27.8% cases. In 19.4% of cases, the disease appeared as pyrexia of unknown etiology and the diagnosis was confirmed by a good therapeutic response to antitubercular therapy. Tuberculosis was diagnosed within 1 year of transplantation in 58.3% of cases. There was no significant difference in the incidence of tuberculosis in patients on different immunosuppressive regimens. The Mantoux test was positive in 33.3% patients. A total of 23 patients were treated with isoniazid and rifampicin, with the addition of a third drug for the first 2 months. Treatment was continued for 9 months in 11 cases with isolated pleuropulmonary disease and for 12-15 months in the other 12 patients. The other 13 were on cyclosporine and were given isoniazid, pyrazinamide, and ethambutol for 18 months. Two patients died of fulminant disease and five more died from unrelated causes. No recurrence of disease has been noted in any of the patients after a mean follow-up of 14.6 months. We conclude that the incidence of tuberculosis in renal allograft recipients in third world countries is much higher than that seen in the western world. Most of the cases are encountered in the first posttransplant year. Tuberculosis must be considered seriously in all patients who have prolonged fever of undetermined etiology. Treatment with isoniazid and rifampicin for 9 months is adequate for patients with localized pleuropulmonary disease. In patients on cyclosporine to whom rifampicin cannot be given because of economic considerations, treatment with isoniazid, pyrazinamide, and ethambutol should be given for 18 months.

Adult↗
PubMed2004

Split-drug regimens for the treatment of patients with sputum smear-positive pulmonary tuberculosis--a unique approach.

OBJECTIVE: To evaluate the efficacy of split-drug regimens for treatment of patients with sputum smear-positive pulmonary tuberculosis in south India. DESIGN: Randomized controlled clinical trial where eligible patients were randomly allocated to: (i) 2RE(3)HZ(3)(alt)/4RH(2) (split I): rifampicin plus ethambutol given on one day and isoniazid plus pyrazinamide the next day for first 2 months followed by rifampicin plus isoniazid twice weekly for 4 months, or (ii) 3RE(3)HZ(3)(alt)/3RH(2) (split II): similar to regimen 1, except duration was 3 months in each phase, or (iii) 2REHZ(3)/4RH(2) (control): rifampicin, isoniazid, ethambutol and pyrazinamide, given thrice weekly for 2 months followed by isoniazid and rifampicin twice weekly for 4 months. All patients were followed up clinically and bacteriologically every month up to 2 years and every 6 months for up to 5 years. RESULTS: A favourable response (cultures negative for Mycobacterium tuberculosis during the last 2 months of treatment) was observed in 91% of 407 patients in split I, 94% of 415 in split II and 89% of 418 in the control regimen. Ninety-one per cent of 370 patients in split I, 93% of 389 in split II and 90% of 370 in control regimens had quiescent disease at the end of 60 months. Gastrointestinal symptoms were more frequent under the control regimen (P = 0.01). CONCLUSION: Split-drug regimens were as effective as the control regimen in terms of favourable response at the end of treatment and quiescent disease at 5 years, and caused fewer gastrointestinal side-effects.

Adult↗
PubMed2005

Treatment of lymph node tuberculosis--a randomized clinical trial of two 6-month regimens.

OBJECTIVE: The currently recommended treatment for lymph node tuberculosis is 6 months of rifampicin and isoniazid plus pyrazinamide for the first 2 months, given either daily or thrice weekly. The objective of this study was to assess the efficacy of a 6-month twice-weekly regimen and a daily two-drug regimen. METHODS: Patients with biopsy confirmed superficial lymph node tuberculosis were randomly allocated to receive either a daily self-administered 6-month regimen of rifampicin and isoniazid, or a twice-weekly, directly observed, 6-month regimen of rifampicin and isoniazid plus pyrazinamide for the first 2 months, in Madurai, South India, Patients were followed up for 36 months after completing treatment. RESULTS: Of 277 enrolled patients, data was available for analysis in 268. At the end of treatment, 116 of 134 [87%; 95% confidence interval (CI) 81-93%] patients in each treatment group had a favourable clinical response; 14 (11%; 95% CI 6-16%) and 17 (13%; 95% CI 7-19%) patients had a doubtful response, and 4 (3%; 95% CI 0-6%) and 1 (1%; 95% CI 0-2%) patients had an unfavourable response among those treated with the daily and twice-weekly regimen, respectively. During 36 months after completion of treatment, five patients [2 (2%; 95% CI 1-3%) and 3 (2%; 95% CI 1-3%) patients treated with the daily and twice-weekly regimen, respectively] had relapse of lymph node tuberculosis, of 260 assessed. Adverse reactions probably attributable to the treatment regimens occurred in 1% of the patients treated daily and in 11% of those treated twice-weekly (P < 0.001). At the end of 36 months after treatment, 126 of 134 (94%; 95% CI 90-98%) and 129 of 134 (96%; 95% CI 94-98%) of the patients treated with the daily and twice-weekly regimen, respectively, had a successful outcome. CONCLUSION: Both the self-administered daily regimen and the fully observed twice-weekly regimen were highly efficacious for treating patients with lymph node tuberculosis and may be considered as alternative options to the recommended regimens.

Adolescent↗
PubMed1985

Safety of thrice-weekly rifampicin for tuberculosis in South-East Asian refugees.

The incidence and types of adverse reactions to rifampicin (in combination with isoniazid, pyrazinamide, and ethambutol) have been studied in 86 South-East Asian refugees treated for tuberculosis in Australia. Most patients received daily therapy initially (mean 3.5 months) followed by supervised thrice-weekly treatment (mean 4.6 months). Minor adverse reactions occurred with similar frequencies during daily (5%) and intermittent (5%) treatment but in no case was modification of rifampicin dosage required. Withdrawal of pyrazinamide was necessary in two patients (2.3%) with clinical hepatitis.

Adolescent↗
PubMed1998

In vitro antimycobacterial activity of 5-chloropyrazinamide.

5-Chloropyrazinamide and 5-chloropyrazinoic acid were evaluated for in vitro activity against Mycobacterium tuberculosis, Mycobacterium bovis, and several nontuberculous mycobacteria by a broth dilution method. 5-Chloropyrazinamide was more active than pyrazinamide against all organisms tested. It is likely that this agent has a different mechanism of action than pyrazinamide.

Antitubercular Agents↗
PubMed1991

Evidence that vesicles containing living, virulent Mycobacterium tuberculosis or Mycobacterium avium in cultured human macrophages are not acidic.

Mycobacterium tuberculosis and Mycobacterium avium multiply in cultured human macrophages (MP) within membrane-enclosed vesicles. These vesicles are generally assumed to be acidic. The evidence most frequently cited for this assumption is that pyrazinamide, which requires an acid pH to be effective, is effective and streptomycin, which loses most of its activity at a low pH, is poorly effective against tubercle bacilli. This assumption was tested by using the two weak bases chloroquine and NH4Cl to raise the pH of acidic vesicles in MP experimentally infected with M. tuberculosis or M. avium. An immunocytochemical locator of acidic regions in the MP was used to monitor the association of intracellular bacilli with acidity. MP were infected with M. tuberculosis or M. avium and incubated with various combinations of the drugs and the weak bases. Replication of the bacteria in the MP was measured by culture counts. Intracellular associations of the mycobacteria with acidity were assessed by electron micrographs and by using the weak base 3-(2,4-dinitroanilino)-3'-amino-N-methyl dipropylamine, which was detected with colloidal gold-labeled antibodies. It was confirmed by immunocytochemistry that both chloroquine and NH4Cl raise the pH of acidic vesicles in the infected MP. However, neither caused any pH-related change in the antimycobacterial activities of pyrazinamide or streptomycin or of the pH-independent drug isoniazid. Immunochemical analyses showed acidity to be associated with killed but not living mycobacteria in the MP. These findings suggest that living M. tuberculosis and M. avium are located in human MP in vesicles which are not acidic.

Ammonium Chloride↗
PubMed1980

Isolated defect in postsecretory reabsorption of uric acid.

A 26-year-old woman was found to have an abnormally sensitive excretory response to a rise in plasma urate with a markedly increased ratio of uric acid to creatinine clearance (exceeding 35%). Uric acid was studied before and after administration of pyrazinamide and benzbromarone. In the presence of pyrazinamide urinary uric acid decreased markedly just as in normal subjects. The uricosuric response to benzbromarone was reduced. No other renal tubular or metabolic abnormalities were found. It appears that the abnormality is related to an isolated defect in postsecretory reabsorption of urate.

Absorption↗