Quantification of Serum Sulfamethoxazole and Trimethoprim by Ultra-fast Solid-Phase Extraction-Tandem Mass Spectrometry.

BACKGROUND: The combination of trimethoprim (TMP) and sulfamethoxazole (SMX) is used to treat a number of bacterial infections. TMP/SMX concentrations in serum are conventionally monitored using high-performance liquid chromatography (HPLC) or liquid chromatography tandem mass spectrometry. These methods require laborious manual extraction techniques and relatively long sample analysis times, necessitating the development of a simple, high-throughput method. A simple, high-throughput method to measure TMP/SMX using ultra-fast solid-phase extraction (SPE)-tandem mass spectrometry has been developed. METHODS: Calibration standards, quality control materials, and patient samples were precipitated with acetonitrile containing isotopically labeled internal standards. Samples were vortexed, centrifuged for 5 minutes at 2053g, and the resulting supernatant was diluted in aqueous mobile phase and injected onto the C18 SPE cartridge. MS/MS analysis was performed by electrospray ionization in positive ion mode at a rate of <20 seconds per sample. A 5-point linear 1/x calibration curve was used to calculate sample concentrations. RESULTS: The intra-assay precision coefficients of variation were <6% and <7% for SMX and TMP, respectively, and <10% for both interassay precision coefficients of variation. Comparison studies using 50 patient and spiked serum samples showed r values of 0.9890 and 0.9853 and y-intercept values of -1.918 and -1.357, respectively compared with the HPLC reference method. All data points were <±15% of the mean. Linearity [r = 0.9952 (SMX) and 0.9954 (TMP)] was established from 12 to 400 mcg/mL with a detection limit of 0.47 mcg/mL, and 1.2-40 mcg/mL with a detection limit of 0.06 mcg/mL, for SMX and TMP, respectively. For either drug, no significant carryover was observed after samples at the upper limit of quantification. No interference was observed from any of the 77 drugs and respective metabolites tested. CONCLUSIONS: A high-throughput SPE-tandem mass spectrometry method for TMP/SMX quantification was developed. The <20 seconds analysis time is a significant improvement compared with traditional HPLC and liquid chromatography tandem mass spectrometry methods, without sacrificing analytical performance.

Concomitant Use of Cotrimoxazole and Atazanavir in HIV-infected Patients: A Therapeutic Drug Monitoring and Pharmacovigilance Based Dual Approach.

BACKGROUND: Cotrimoxazole is the main antibiotic used in primary prophylaxis for opportunistic infections in advanced HIV infection. This drug can inhibit one of the metabolic pathways of atazanavir (ATV), such as the cytochromes P450 (CYP) 2C8/2C9 and could interfere with its safety and efficacy. OBJECTIVE: We studied the drug-drug interaction (DDI) between cotrimoxazole and ATV by using therapeutic drug monitoring (TDM) and pharmacovigilance (PV) approaches. METHODS: We compared a group of patients treated with cotrimoxazole and receiving an ATV-based regimen to controls. This historical cohort analysis used data from Dat'AIDS in HIV-infected patients who had at least two lowest plasma concentrations (C-trough) of ATV during their outpatient follow-up. Likewise, we used the international pharmacovigilance data from VigiBase to evaluate the notifications of hyperbilirubinemia reported with ATV. RESULTS: In the TDM analysis, the two groups of patients (treated with cotrimoxazole and controls) were almost homogeneous concerning the main baseline features. After at least six months of ATVbased regimen, there was no significant difference in the safety threshold of the ATV C-trough [with an adjusted odds ratio (aOR) of 1.4 (95% CI: 0.5 - 4.4)] compared to controls. We observed similar results with the efficacy thresholds of ATV C-trough. Regarding the PV analysis, there was no difference in hyperbilirubinemia occurring with ATV when cotrimoxazole was concomitant, with an adjusted reporting odds ratio (aROR) of 0.9 (95% CI: 0.6 to 1.2). CONCLUSION: This study showed a relevant concomitant use between Cotrimoxazole and ATV based on TDM and PV approaches.

Physiologically Based Pharmacokinetic Modeling for Trimethoprim and Sulfamethoxazole in Children.

OBJECTIVE: The aims of this study were to (1) determine whether opportunistically collected data can be used to develop physiologically based pharmacokinetic (PBPK) models in pediatric patients; and (2) characterize age-related maturational changes in drug disposition for the renally eliminated and hepatically metabolized antibiotic trimethoprim (TMP)-sulfamethoxazole (SMX). METHODS: We developed separate population PBPK models for TMP and SMX in children after oral administration of the combined TMP-SMX product and used sparse and opportunistically collected plasma concentration samples to validate our pediatric model. We evaluated predictability of the pediatric PBPK model based on the number of observed pediatric data out of the 90% prediction interval. We performed dosing simulations to target organ and tissue (skin) concentrations greater than the methicillin-resistant Staphylococcus aureus (MRSA) minimum inhibitory concentration (TMP 2 mg/L; SMX 9.5 mg/L) for at least 50% of the dosing interval. RESULTS: We found 67-87% and 71-91% of the observed data for TMP and SMX, respectively, were captured within the 90% prediction interval across five age groups, suggesting adequate fit of our model. Our model-rederived optimal dosing of TMP at the target tissue was in the range of recommended dosing for TMP-SMX in children in all age groups by current guidelines for the treatment of MRSA. CONCLUSION: We successfully developed a pediatric PBPK model of the combination antibiotic TMP-SMX using sparse and opportunistic pediatric pharmacokinetic samples. This novel and efficient approach has the potential to expand the use of PBPK modeling in pediatric drug development.

Suboptimal cotrimoxazole prophylactic concentrations in HIV-infected children according to the WHO guidelines.

AIMS: A clinical study was conduct in HIV-infected children to evaluate the prophylactic doses of cotrimoxazole [sulfamethoxazole (SMX) and trimethoprim (TMP)] advised by the WHO. METHODS: Children received lopinavir-based antiretroviral therapy with cotrimoxazole prophylaxis (200 mg of SMX/40 mg of TMP once daily). A nonlinear mixed effects modelling approach was used to analyse plasma concentrations. Factors that could impact the pharmacokinetic profile were investigated. The model was subsequently used to simulate individual exposure and evaluate different administration schemes. RESULTS: The cohort comprised 136 children [average age: 1.9 years (range: [0.7-4]), average weight: 9.5 kg (range: [6-16.3])]. A dose per kg was justified by the significant influence of implementing an allometrically scaled body size covariate on SMX and TMP pharmacokinetics. SMX and TPM clearance were estimated at 0.49 l h-1 /9.5 kg and 3.06 l h-1 /9.5 kg, respectively. The simulated exposures obtained after administration of oral dosing recommended by the WHO for children from 10 to 15 kg were significantly lower than in adults for SMX and TMP. This could induce a reduction of effectiveness of cotrimoxazole. Simulations show that regimens of 30 mg kg-1 of SMX and 6 mg kg-1 of TMP in the 5-10 kg group and 25 mg kg-1 of SMX and 5 mg kg-1 of TMP in the 10-15 kg group are more suitable doses. CONCLUSIONS: In this context of high prevalence of opportunistic infections, a lower exposure to cotrimoxazole in children than adults was noted. To achieve comparable exposure to adults, a dosing scheme per kg was proposed.

Immunogenicity of trimethoprim/sulfamethoxazole in a macaque model of HIV infection.

BACKGROUND: Sulfonamide hypersensitivity has a high incidence in HIV infection and correlates with low CD4+ counts, but the mechanisms are not understood. The aims of this study were to determine whether trimethoprim/sulfamethoxazole (TMP/SMX) led to SMX adduct formation, immunogenicity, or signs of drug hypersensitivity in SIV-infected rhesus macaques, and whether differences in antioxidants, pro-inflammatory mediators, or SMX disposition were predictive of drug immunogenicity. METHODS: Nine macaques chronically infected with SIVmac239 and 7 non-infected controls were studied. Baseline blood ascorbate, glutathione, IFN-γ, LPS, sCD14, and cytochrome b5 reductase measurements were obtained, macaques were dosed with TMP/SMX (120mg/kg/day p.o. for 14days), and SMX metabolites, lymph node drug adducts, drug-responsive T cells, and anti-SMX antibodies were measured. RESULTS: Four of 9 of SIV-positive (44%), and 3 of 7 SIV negative (43%) macaques had drug-responsive T cells or antibodies to SMX. Two macaques developed facial or truncal rash; these animals had the highest levels of lymph node drug adducts. Antioxidants, pro-inflammatory mediators, and SMX metabolites were not predictive of drug immunogenicity; however, the Mamu DRB1*0401/0406/0411 genotype was significantly over-represented in immune responders. CONCLUSIONS: Unlike other animal models, macaques develop an immune response, and possible rash, in response to therapeutic dosages of TMP/SMX. Studying more animals with CD4+ counts <200cells/µl, along with moderately restricted ascorbate intake to match deficiencies seen in humans, may better model the risk of SMX hypersensitivity in HIV-infection. In addition, the role of Mamu-DRB1 genotype in modeling drug hypersensitivity in retroviral infection deserves further study.

Pharmacokinetics of mefloquine and its effect on sulfamethoxazole and trimethoprim steady-state blood levels in intermittent preventive treatment (IPTp) of pregnant HIV-infected women in Kenya.

BACKGROUND: Intermittent preventive treatment in pregnancy with sulfadoxine/pyrimethamine is contra-indicated in HIV-positive pregnant women receiving sulfamethoxazole/trimethoprim prophylaxis. Since mefloquine is being considered as a replacement for sulfadoxine/pyrimethamine in this vulnerable population, an investigation on the pharmacokinetic interactions of mefloquine, sulfamethoxazole and trimethoprim in pregnant, HIV-infected women was performed. METHODS: A double-blinded, placebo-controlled study was conducted with 124 HIV-infected, pregnant women on a standard regimen of sulfamethoxazole/trimethoprim prophylaxis. Seventy-two subjects received three doses of mefloquine (15 mg/kg) at monthly intervals. Dried blood spots were collected from both placebo and mefloquine arms four to 672 h post-administration and on day 7 following a second monthly dose of mefloquine. A novel high-performance liquid chromatographic method was developed to simultaneously measure mefloquine, sulfamethoxazole and trimethoprim from each blood spot. Non-compartmental methods using a naïve-pooled data approach were used to determine mefloquine pharmacokinetic parameters. RESULTS: Sulfamethoxazole/trimethoprim prophylaxis did not noticeably influence mefloquine pharmacokinetics relative to reported values. The mefloquine half-life, observed clearance (CL/f), and area-under-the-curve (AUC0→∞) were 12.0 days, 0.035 l/h/kg and 431 µg-h/ml, respectively. Although trimethoprim steady-state levels were not significantly different between arms, sulfamethoxazole levels showed a significant 53% decrease after mefloquine administration relative to the placebo group and returning to pre-dose levels at 28 days. CONCLUSIONS: Although a transient decrease in sulfamethoxazole levels was observed, there was no change in hospital admissions due to secondary bacterial infections, implying that mefloquine may have provided antimicrobial protection.

Quantification of co-trimoxazole in serum and plasma using MS/MS.

BACKGROUND: Co-trimoxazole is frequently used in the prophylaxis and treatment of Pneumocystis carinii pneumonia. High plasma concentrations of sulfamethoxazole or trimethoprim are correlated with toxicity. There is, however, a large variation in PK observed which can lead to underexposure or toxicity. RESULTS: We developed a novel LC-MS/MS method to analyze the components of co-trimoxazole, trimethoprim and sulfamethoxazole and its metabolite sulfamethoxazole-N-acetyl. This new method is expeditious due to its limited sample preprocessing and a relatively short run-time of only 3 min. CONCLUSION: This new method met the US FDA requirements on linearity, selectivity, precision, accuracy, matrix effects, recovery and stability and is suitable for routine analysis and future prospective studies.

Simultaneous determination of trimethoprim and sulfamethoxazole in dried plasma and urine spots.

BACKGROUND: Trimethoprim-sulfamethoxazole (TMP-SMX) is an antimicrobial drug combination commonly prescribed in children and adults. The study objectives were to validate and apply an HPLC-MS/MS method to quantify TMP-SMX in dried plasma spots (DPS) and dried urine spots (DUS), and perform a comparability analysis with liquid matrices. RESULTS: For TMP the validated range was 100-50,000 ng/ml for DPS and 500-250,000 ng/ml for DUS; for SMX, the validated range was 1000-500,000 ng/ml for both DPS and DUS. Good agreement was noted between DPS/DUS and liquid plasma and urine samples for TMP, while only modest agreement was observed for SMX in both matrices. CONCLUSION: A precise, accurate and reproducible method was developed to quantify TMP-SMX in DPS and DUS samples.

Trimethoprim and sulfamethoxazole transmembrane clearance during modeled continuous renal replacement therapy.

BACKGROUND/AIMS: There is limited data regarding trimethoprim (TMP)/sulfamethoxazole (SMX) continuous renal replacement therapy (CRRT) dosing. We aimed to estimate TMP/SMX transmembrane clearance (CLtm) during continuous hemofiltration (CH) and continuous hemodialysis (CD) to guide dosing. METHODS: Using an in vitro model, TMP/SMX sieving coefficients (SC) and saturation coefficients (SA) were determined with high-flux polyarylethersulfone and polyacrylonitrile-sodium methallyl sulfonate copolymer hemodiafilters at ultrafiltration/dialysate rates of 1, 2, 3, and 6 l/h. TMP/SMX CLtm was calculated using measured SC and SA. TMP/SMX CRRT doses were modeled using CLtm and published TMP/SMX pharmacokinetic parameters. RESULTS: TMP SC/SA during CH/CD were significantly higher than SMX SC/SA. During modeling, TMP 10 mg/kg/day and its corresponding SMX dose, 50 mg/kg/day, resulted in steady state TMP/SMX peak concentrations associated with efficacy against Pneumocystis jirovecii. CONCLUSIONS: CRRT resulted in greater TMP CLtm than SMX. TMP 10 mg/kg/day divided q12h may be an appropriate initial dose to consider in patients undergoing CRRT.

Cotrimoxazole plasma levels, dialyzer clearance and total removal by extended dialysis in a patient with acute kidney injury: risk of under-dosing using current dosing recommendations.

BACKGROUND: Dosing of antibiotics in critically ill patients is challenging. It becomes even more difficult if renal or hepatic impairment ensue. Modern means of renal replacement therapy are capable of removing antibiotics to a higher rate than decades ago, leaving clinicians with a high degree of uncertainty concerning the dose of antibiotics in this patient population. Cotrimoxazole, a combination of trimethoprim (TMP) and sulfamethoxazole (SMX) is frequently used in the treatment of several infections including Pneumocystis jirovecii pneumonia (PCP). CASE PRESENTATION: Here we describe a patient with acute kidney injury in which we investigated the TMP and SMX levels during the course of an ICU stay. Cotrimoxazole was administered every six hours i.v. in a dose of TMP/SMX 15/75 mg/kg/day. Extended dialysis was performed with a high-flux dialyzer. Blood samples, as well as pre- and postdialyzer samples and aliquots of the collected spent dialysate were collected.Observed peak concentrations (Cmax) were 7.51 mg/l for TMP and 80.80 mg/l for SMX. Decline of blood levels during extended dialysis (TMP 64%; SMX 84%) was mainly due to removal by the dialysis procedure, illustrated by the high dialyzer clearances (median of 4 extended dialysis sessions: TMP 94.0 / SMX 51.0 ml/min), as well as by the absolute amount of both substances in the collected spent dialysate (median of 6 extended dialysis sessions: TMP 556 mg / SMX 130 mg). Within the limitation of a case report our data from 4 consecutive extended dialysis sessions suggest that this procedure substantially removes both TMP and SMX. CONCLUSIONS: Dose reduction, which is usually advocated in patients with acute kidney injury under renal replacement therapy, might lead to significant under-dosing. Pharmacokinetic studies for TMP/SMX dosing in this patient population are necessary to allow adequate dosing.

Daptomycin plus trimethoprim/sulfamethoxazole combination therapy in post-neurosurgical meningitis caused by linezolid-resistant Staphylococcus epidermidis.

Post-neurosurgical infection is a serious complication that occurs in approx. 4% of all patients undergoing neurosurgical procedures and is associated with high morbidity and mortality rates and prolonged length of intensive care unit (ICU) stay. Coagulase-negative staphylococci (CoNS), especially methicillin-resistant Staphylococcus epidermidis (MRSE), are the most frequent pathogens involved in CNS post-neurosurgical meningitis. Treatment is challenging especially in patients with meningitis due to multidrug- resistant (MDR) CONS. Herein, we report a unique case of post-neurosurgical meningitis due to MRSE resistant to linezolid (a molecular analysis revealed the presence of the mutation G2576T on domain V of the 23S rRNA gene) and with reduced susceptibility to glycopeptides, successfully treated with a combination of daptomycin at 10 mg/kg daily plus trimethoprim/sulfamethoxazole (TMP/SMX). This antibiotic combination showed an indifferent interaction in in vitro studies. Daptomycin serum and cerebrospinal fluid (CSF) concentrations, determined through blood and CSF samples drawn just prior to and 4 h after the third dose, were 18.9-0.78 and 51.65-3.1 mg/L, respectively. These values allowed us to approximate a 5-6% penetration rate of the drug through an inflamed blood-brain barrier. In conclusion, although further studies are needed, combination of high-dose daptomycin plus TMP/SMX is a reasonable option for treatment of meningitis caused by multidrug-resistant S. epidermidis.

Trimethoprim/Sulfamethoxazole pharmacokinetics in two patients undergoing continuous venovenous hemodiafiltration.

OBJECTIVE: To determine the extent of elimination of trimethoprim (TMP) and sulfamethoxazole (SMX) via continuous venovenous hemodiafiltration (CVVHDF) in 2 critically ill patients with renal failure. CASE SUMMARY: A 62-year-old woman with Pneumocystis jirovecii pneumonia (PCP) was admitted to our intensive care unit for severe acute respiratory distress syndrome. A 77-year-old man was admitted for aortic root replacement and developed septic shock and nosocomial pneumonia due to Stenotrophomonas maltophilia. Both patients developed acute renal failure, necessitating CVVHDF. They were treated with intravenous TMP/SMX adapted to renal function. The first patient received TMP 6.4 mg/kg/day and SMX 32 mg/kg/day, corresponding to 50% of the recommended high-dose TMP/SMX regimen in PCP patients. The second patient received TMP 1.7 mg/kg/day and SMX 8.6 mg/kg/day, corresponding to 50% of the usual dose in bacterial infections. We determined peak and trough serum TMP and SMX concentrations and the extent of TMP/SMX CVVHDF clearance at steady-state while the patients were still anuric and oliguric. DISCUSSION: Data on TMP and SMX pharmacokinetics in CVVHDF are lacking and dosing recommendations are inconclusive. In both patients, CVVHDF clearance of TMP ranged from 21.5 to 28.9 mL/min, corresponding with normal renal clearance (20-80 mL/min). SMX clearance in CVVHDF showed high variability (18.7, 26.7, and 42.6 mL/min) and exceeded renal clearance values in normal renal function (1-5 mL/min). Accordingly, peak TMP serum concentrations were within the recommended range in the patient treated with a reduced TMP/SMX dose for PCP, whereas her SMX peak concentrations were only one third of recommended target concentrations. CONCLUSIONS: Our data indicate that both TMP and SMX are removed by CVVHDF to a significant degree, and dose reduction of TMP/SMX in CVVHDF bears the risk of underdosing. Given variability in drug exposure in critically ill patients, therapeutic drug monitoring is advisable in anuric or oliguric patients undergoing continuous renal replacement therapy to ensure optimal TMP/SMX dosing.

Development and validation of an HPLC method for simultaneous determination of trimethoprim and sulfamethoxazole in human plasma.

The combination of trimethoprim (TMP) and sulfamethoxazole (SMX) is used in the treatment of many common infections such as urinary, respiratory and gastrointestinal tract infections. The aim of this study was to determine TMP and SMX simultaneously in human plasma samples by high performance liquid chromatography (HPLC) using antipyrine as the internal standard. Separation of the compounds was achieved on a reverse-phase C8 column packed with 5 microm dimethyl octadecylsilyl bonded amorphous silica (4.6 mm x 250 mm) column using a mobile phase consisted of potassium hydrogen phosphate, acetonitrile, methanol and water adjusted to pH 6.2. The mobile phase was delivered at a flow rate of 1 mL min- and the effluent was monitored using Max plot technique at 25 derees C. Retention times were 5 min for TMP, 7 min for antipyrine and 9 min for SMX. Quantitation limits were 10 ng mL(-1) for TMP and 50 ng mL(-1) for SMX. Our findings indicated that the developed HPLC method was precise, accurate, specific and sensitive for simultaneous determination of TMP and SMX. Proposed HPLC method was successfully applied for the analysis of TMP and SMX in human plasma after oral administration of a co-trimoxazole tablet to human volunteers.

The effects of cotrimoxazole or tenofovir co-administration on the pharmacokinetics of maraviroc in healthy volunteers.

AIMS: To assess the potential of cotrimoxazole and tenofovir, drugs which are inhibitors and/or substrates of renal transporters, to alter the pharmacokinetic profile of maraviroc. METHODS: Two randomized, placebo-controlled, two-way crossover studies were conducted in healthy male and female subjects. In study 1, 16 subjects, aged 18-45 years, received maraviroc (300 mg b.i.d.) with and without cotrimoxazole (960 mg b.i.d.; 160 mg trimethoprim and 800 mg sulfamethoxazole). In study 2, 12 subjects, aged 21-45 years, received maraviroc (300 mg b.i.d.) with and without tenofovir (300 mg q.d.). For study 1, blood was collected predose and on days 1-7. In study 2, blood was collected predose, on day 1 and days 3-7. In both studies, blood was collected at intervals up to 12 h postdose on day 7. Urine was collected on day 7, 0-12 h post morning dose. Blood and urine were analysed for maraviroc using liquid chromatography/tandem mass spectrometry. RESULTS: The geometric mean ratios for C(max) and AUC(12) were 119% and 111%, respectively, for maraviroc plus cotrimoxazole and 104% and 103%, respectively, for maraviroc plus tenofovir, compared with maraviroc plus placebo. Renal clearance of maraviroc plus placebo was 8.3 l h(-1) and 8.5 l h(-1) and was 7.8 l h(-1) for maraviroc plus cotrimoxazole and maraviroc plus tenofovir. There were no serious or severe adverse events or any clinically significant changes in laboratory tests, blood pressure, or electrocardiograms. CONCLUSIONS: Neither cotrimoxazole nor tenofovir caused a clinically significant effect on the pharmacokinetics of maraviroc. Maraviroc 300 mg b.i.d. was well tolerated when co-administered with either cotrimoxazole or tenofovir.

Rapid and simultaneous determination of sulfamethoxazole and trimethoprim in human plasma by high-performance liquid chromatography.

A simple and reproducible high-performance liquid chromatographic method was developed for simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP) in human plasma. The method entailed injection of the samples after deproteination with perchloric acid and subsequent neutralizing. Primidone was used as internal standard. Chromatography was performed on a C(18) column (250 mm x 4.6 mm, 5 microm) under isocratic elution with 50 mM aqueous sodium dihydrogen phosphate-acetonitrile-triethylamine (100:25:0.5, v/v), pH 5.9. Detection was made at 240 nm and analyses were run at a flow-rate of 1.5 ml/min at a temperature of 35 degrees C. The recovery was 83.4, 88.5 and 98.2% for TMP, SMX and internal standard, respectively. The precision of the method was 2.6-9.8% over the concentration range of 0.125-2 microg/ml for TMP and 0.39-50 microg/ml for SMX. The limit of quantification (LOQ) in plasma was 0.125 and 0.39 microg/ml for TMP and SMX, respectively. The method was used for a bioequivalence study.

Zidovudine plus sulfamethoxazole-trimethoprim adversely affects B lymphocyte maturation in bone marrow of normal mice.

Sulfamethoxazole-trimethoprim and zidovudine (AZT), drugs used often in combination in patients infected with HIV, were investigated for their effects on B cell development in a mouse model. BALB/c mice were randomized to receive oral doses of AZT, sulfamethoxazole-trimethoprim, or the combination via oral gavage for up to 28 days. Immune cell populations in the spleen, lung, and peripheral blood were examined, and toxicity to B lineage subtypes in the bone marrow was investigated by phenotypic analysis via flow cytometry. Pre-pro-B, pro-B, early pre-B, and late pre-B cells were assayed for apoptosis and analyzed for cell cycle profile. Total as well as B cell splenic and bone marrow cellularities were significantly decreased by using the drugs concomitantly, while B cell populations in the lungs and percentage in the peripheral blood were not affected. Combination therapy caused significant increases in apoptosis in B cells and granulocytes in the bone marrow, with the late pre-B cell population being the most depleted. The proliferative expansion and differentiation of early pre-B cells (B220+/CD43+/BP-1+/HSA+) to the late pre-B cell (B220+/CD43-/IgM-) stage was blocked, with early pre-B cells accumulating in the proliferative phases of the cell cycle. This apoptosis increase is likely due to elevated blood sulfamethoxazole concentrations that were observed in mice also receiving AZT. Concurrent sub-chronic administration of AZT and sulfamethoxazole-trimethoprim adversely affected B lymphocyte development in mouse bone marrow.

Response of Plasmodium falciparum to cotrimoxazole therapy: relationship with plasma drug concentrations and dihydrofolate reductase and dihydropteroate synthase genotypes.

We assessed the efficacy of trimethoprim/sulfamethoxazole (TRM/SMX) in vivo in relation to the frequency of dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) alleles in 45 Sudanese malaria patients. Plasma levels of TRM, SMX, and acetylsulfamethoxazole (AcSMX) were measured before treatment and at days 3, 7, and 14 or upon recrudescence to ascertain drug absorption. Forty patients (89%) had an adequate clinical response, one patient (2%) had an early treatment failure response, while four patients (8%) showed late treatment failure responses. Genotyping of merozoite surface protein 1, MSP-1, MSP-2, and glutamate-rich protein before treatment and upon recrudescence showed that all recurring parasites were recrudescences. The plasma levels of TRM, AcSMX, and SMX indicated adequate drug absorption in all patients. This suggests parasite resistance as a cause of treatment failure. The presence of dhfr Ile 51 and Asn 108 alone or coupled with dhps Ala-436 among parasites that were cleared after treatment indicates that these alleles alone are insufficient to cause in vivo resistance. However, the presence of the triple mutant dhfr (Ile-51/Arg-59/Asn-108) with the dhps Gly-437 genotype in all recurring infections, suggests the importance of codon 59 and 437 alleles in susceptibility to TRM/SMX. However, the number is too little to make firm conclusions.

Adverse reactions to trimethoprim/sulfamethoxazole in AIDS.

OBJECTIVE: To report the case of a woman with AIDS who developed tremor, acute pancreatitis, and elevated serum creatinine levels while receiving trimethoprim/sulfamethoxazole (TMP/SMX). CASE SUMMARY: A 37-year-old Puerto Rican woman with AIDS, HIV nephropathy, and a recent history of disseminated histoplasmosis presented with fever, nonproductive cough, pancytopenia, and elevated transaminase and alkaline phosphatase levels. Serum creatinine was near her baseline level of 2.9 mg/dL. Treatment was started with amphotericin B lipid complex for histoplasmosis and intravenous TMP/SMX for presumed Pneumocystis carinii pneumonia. Two days later, the patient developed a high-frequency tremor and severe abdominal pain, and serum creatinine increased to 5.6 mg/dL. TMP/SMX was discontinued, after which the patient's symptoms resolved within 72 hours and serum creatinine returned to baseline levels. DISCUSSION: A high incidence of adverse reactions to TMP/SMX has been reported among HIV-infected persons. Toxic sulfamethoxazole metabolites may elicit hypersensitivity reactions. Trimethoprim can inhibit renal creatinine secretion, leading to high serum creatinine levels. Trimethoprim also inhibits dihydrofolate reductase, causing decreased dopamine production, which may lead to parkinsonian symptoms. Use of the Naranjo probability scale indicated a probable relationship between the adverse effect and TMP/SMX. CONCLUSIONS: The high frequency and wide range of potential adverse effects associated with the use of TMP/SMX in HIV-infected persons require that clinicians consider drug toxicity as a cause of new symptoms in patients receiving this medication.

A comparison of antibiotic regimens in the treatment of acute melioidosis in a mouse model.

Melioidosis is caused by the Gram-negative bacillus Burkholderia pseudomallei. Most clinical reports of disease are from south-east Asia and northern Australia. The organism is intrinsically resistant to most commonly available antibiotics. Standard therapy includes ceftazidime either alone or in combination with co-trimoxazole. The clinical advantage in adding co-trimoxazole has never been determined; nor has the activity of newer, fourth-generation cephalosporins, such as cefepime, been studied in the treatment of this condition. BALB/c mice have been shown to represent an animal model of melioidosis. This animal model was used in this study to compare the efficacy of ceftazidime and cefepime alone or with co-trimoxazole, in the therapy of melioidosis. Antibiotic levels in the mice were determined by HPLC, and dosing was modified to keep plasma antibiotic levels at or above the MIC for the organism-antibiotic combination for a significant part of a 12 h period. Bacterial load, as determined by splenic counts, showed that ceftazidime in combination with co-trimoxazole was the most effective therapeutic option. The animal model described in this study can be used as a preliminary evaluation of therapeutic options for melioidosis.

Pharmacokinetics and bioavailability of trimethoprim-sulfamethoxazole in alpacas.

The pharmacokinetics and bioavailability of trimethoprim-sulfamethoxazole (TMP-SMX) were studied in six healthy male-castrate alpacas (Lama pacos) after intravenous (i.v.) or oral (p.o.) drug administration of 15 mg/kg TMP-SMX using a crossover design with a 2-week washout period. After 90 days one group (n = 3) was given a p.o. dose of 30 mg/kg TMP-SMX and the other group (n = 3) was given a p.o. dose of 60 mg/kg TMP-SMX. After i.v. administration of 15 mg/kg of TMP-SMX the mean initial plasma concentration (C0) was 10.75 +/- 2.12 microg/mL for trimethoprim (TMP) and 158.3 +/- 189.3 microg/mL for sulfamethoxazole (SMX). Elimination half-lives were 0.74 +/- 0.1 h for TMP and 2.2 +/- 0.6 h for SMX. The mean residence times were 1.45 +/- 0.72 h for TMP and 2.8 +/- 0.6 h for SMX. The areas under the respective concentration vs. time curves (AUC) were 2.49 +/- 1.62 microg h/mL for TMP and 124 +/- 60 microg h/mL for SMX. Total clearance (Clt) for TMP was 21.63 +/- 9.85 and 1.90 +/- 0.77 mL/min kg for SMX. The volume of distribution at steady state was 2.32 +/- 1.15 L/kg for TMP and 0.35 +/- 0.09 L/kg for SMX. After intragastric administration of 15, 30 and 60 mg/kg the peak concentration (Cmax) of SMX were 1.9 +/- 0.8, 2.6 +/- 0.4 and 2.8 +/- 0.7 microg/mL, respectively. The AUC was 9.1 +/- 5, 25.9 +/- 3.3 and 39.1 +/- 4.1 microg h/mL, respectively. Based upon these AUC values and correcting for dose, the respective bioavailabilities were 7.7, 10.5 and 7.94%. Trimethoprim was not detected in plasma after intragastric administration. These data demonstrate that therapeutic concentrations of TMP-SMX are not achieved after p.o. administration to alpacas.