Observational study of the clinical utility of sulfamethoxazole serum level monitoring in the treatment of brain abscesses due to Nocardia species

Although there is a lack of data in trimethoprim-sulfamethoxazole (TMP-SMX) serum monitoring utility for invasive nocardial infections, therapeutic drug monitoring is widely used to optimize dosing and avoid adverse reactions that may cause treatment interruption.We retrospectively reviewed all adults who received TMP-SMX to treat nocardial brain abscess and had SMX serum level testing from 2010 to 2020.Twenty-two patients received treatment with TMP-SMX for Nocardia species brain abscess and 16 (72.7%) had a reported SMX level, with a median patient age of 65.5 years (interquartile range, IQR 59.5-72.5). Compared to those who did not have a documented SMX serum level, patients with SMX levels had a shorter median course of TMP-SMX treatment (322 days [IQR 188-365] vs. 365 [IQR 224-365]; P = .31) and higher therapeutic induction dose (10 [62.5%] vs. 3 [50%]; P = .92). Similarly, they were more frequently on hemodialysis (3 [13.6%] vs. 1 [4.5%]; P = > .99). The median peak level was 158.5 (IQR 120-218) μg/mL, collected at 2 hours (75%) post-administration in the induction phase (81.3%). Patients with documented SMX levels had fewer reported drug toxicity (5 [31.3%] vs. 4 [66.7%]; P = .1) than those without SMX levels. Among the five patients who reported TMP-SMX-related toxicity, 4 (80%) had an SMX peak level >150 μg/mL. There was no difference in the cure, relapse, and death rates among the two groups.While SMX level was not associated with Nocardia species brain abscess cure rates and mortality, most patients with SMX peak >150 μg/mL experienced drug toxicity.

Pharmacokinetic study of seven bioactive components of Xiaoyan Lidan Formula in cholestatic and control rats using UPLC-MS/MS

A rapid, sensitive, and reliable ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method has been developed to simultaneously determine the major bioactive components of Xiaoyan Lidan Formula (XYLDF) in rat plasma, using sulfamethoxazole as the internal standard (IS). The seven major bioactive components are andrographolide, dehydroandrographolide, enmein, 1-methoxicabony-β-carboline, 4,5-dimethoxy-canthin-6-one, 4-methoxy-5-hydroxy-canthin-6-one, and 1-hydroxymethyl-β-carboline. After pretreating by protein precipitation with methanol, separation was performed on a UPLC C18 column using gradient elution with a mobile phase consisting of acetonitrile and 0.1% formic acid at a flowing rate of 0.7 mL/min. Detection was performed on TSQ Quantum mass spectrometry set at the positive/negative ionization and multiple reaction monitoring (MRM) mode. The intra- and inter-day precision were less than 9.8%, whereas the intra- and inter-day accuracy were within ± 13.4%. The method was validated and applied to compare the pharmacokinetic profiles of the analytes in serum of Alpha-naphthylisothiocyanate (ANIT)-induced cholestasis and control rats after oral administration of XYLDF. The results showed remarkable differences in pharmacokinetic properties of the analytes between cholestatic (model) and control groups, thereby providing essential scientific information for better understanding of mechanism of XYLDF and a reference for its clinical applications.

[Pharmacokinetics of sulfamethoxazole in healthy Han volunteers living at plain and in native Han and Tibetan healthy volunteers living at high altitude]

The paper is to report the pharmacokinetics of sulfamethoxazole in healthy Han volunteers living at plain (PH) and native Han and Tibetan healthy volunteers living at high altitude (HNH and HNT). After healthy volunteers were administrated orally cotrimoxazole tablets, plasma concentration of sulfamethoxazole and metabolite N4-acetylsulfamethoxazole was determined by RP-HPLC, and plasma concentration-time data were analyzed by DAS 2.0 software to get the related pharmacokinetic parameters. The main pharmacokinetic parameters t(1/2) of sulfamethoxazole in PH, HNH and HNT were, respectively, 9.30 +/- 1.11, 10.99 +/- 1.23 and 10.44 +/- 1.05 h; tmax were 1.4 +/- 0.3, 2.0 +/- 1.1 and 1.8 +/- 0.4 h; Cmax were 94.42 +/- 15.26, 89.33 +/- 7.67 and 87.43 +/- 11.61 micro x mL(-1); AUC(0-t) were 1202.5 +/- 238.3, 1 434.7 +/- 193.9 and 1302.8 +/- 103.0 microg x h x mL(-1); AUC(0-infinity) were 1240.7 +/- 255.3, 1511.5 +/- 211.9 and 1363.9 +/- 116.5 microg x h x mL(-1); CL were 1.01 +/- 0.22, 0.81 +/- 0.12 and 0.89 +/- 0.08 L x h(-1) x kg(-1); V were 13.27 +/- 1.73, 12.81 +/- 2.15 and 13.28 +/- 1.20 L x kg(-1). Sulfamethoxazole pharmacokinetic parameters of HNH and HNT were significantly different from that of PH. The t(1/2) was significantly higher and the CL was significantly lower in HNH and HNT than that in PH, and the AUC(0-infinity) was significantly lower in HNT compared with HNH. This study found significant changes in the disposition of sulfamethoxazole under the special environment of high altitude hypoxia. This finding may provide some references for clinical rational application of sulfamethoxazole in HNH and HNT.

Simultaneous determination and validation of antimicrobials in plasma and tissue of actinomycetoma by high-performance liquid chromatography with diode array and fluorescence detection

A simple, precise, and reliable chromatographic method was developed for the simultaneous determination in plasma and infected tissue of five antimicrobials proposed for the treatment of actinomycotic mycetoma: amoxicillin, trimethoprim, linezolid, sulfamethoxazole and garenoxacin. Separation of the analytes was achieved on an Atlantis dC18 column (150 mm x 4.6 mm, ID 5 microm) with a mobile phase composed of acetonitrile and trifluoroacetic acid (ATF) 0.1% (v/v) using a gradient program. The detection was carried out using a diode array detector at 254 nm and in a fluorescence detector at wavelengths of excitation and emission of 292 nm and 392 nm for linezolid and sulfamethoxazole, and 292 nm and 408 nm for garenoxacin, respectively. The intraday precision was in the range of 0.7-15% of relative standard deviations (%R.S.D.) for plasma and 1-18% for tissue. Linearity range was from 2.4 to 20 microg/ml for amoxicillin, 0.3 to 20 microg/ml for trimethoprim, sulfamethoxazole and linezolid, and 0.3 to 10 microg/ml for garenoxacin. Acetonitrile was used to precipitate proteins from plasma. Recoveries in plasma ranged from 71% to 118% and in infected tissue from 78% to 122%. Limits of detection (LODs) were 1.2 and 0.5 microg/ml for amoxicillin in plasma and tissue, respectively and 0.15 and 1.2 microg/ml in plasma and tissue, respectively for the other antimicrobials. The method can be applied for individual or simultaneous determination of the antimicrobials in plasma and tissue of mouse infected with actinomycetoma.

Micellar electrokinetic chromatography method for the determination of sulfamethoxazole, trimethoprim and their main metabolites in human serum

A complete analytical procedure, including sample clean-up and a micellar electrokinetic chromatographic method, is presented for the determination of sulfamethoxazole, trimethoprim, and their main metabolites by using 20 mmol L(-1) borate buffer (pH 9.3), 25 mmol L(-1) sodium dodecylsulfate, and 5% v/v acetonitrile as electrolyte. The separation was carried out at 30 kV and 20 degrees C in a fused silica capillary (60.2 cm x 75 microm inner diameter) fitted with a window in the capillary cartridge of 100 x 800 microm. The detector response was linear from the limit of quantification to 3 mg L(-1) for the individual components. The limits of quantification ranged from 0.13 up to 0.24 mg L(-1). The method was applied to human serum, previously spiked at different concentrations of all the analytes, and recoveries between 95% and 108% were obtained.

The effect of clarithromycin, fluconazole, and rifabutin on sulfamethoxazole hydroxylamine formation in individuals with human immunodeficiency virus infection (AACTG 283)

BACKGROUND

Sulfamethoxazole hydroxylamine formation, in combination with long-term oxidative stress, is thought to be the cause of high rates of adverse drug reactions to sulfamethoxazole in human immunodeficiency virus (HIV)-infected subjects. Therefore the goal of this study was to determine the effect of fluconazole, clarithromycin, and rifabutin on sulfamethoxazole hydroxylamine formation in individuals with HIV-1 infection.

METHODS

HIV-1-infected subjects (CD4 + count >/=200 cells/mm 3 ) were enrolled in a 2-part (A and B), open-label drug interaction study (Adult AIDS Clinical Trial Group [AACTG] 283). In part A (n = 9), subjects received cotrimoxazole (1 tablet of 800 mg sulfamethoxazole/160 mg trimethoprim daily) alone for 2 weeks and then, in a randomly assigned order, cotrimoxazole plus either fluconazole (200 mg daily), rifabutin (300 mg daily), or fluconazole plus rifabutin, each for a 2-week period. Part B (n = 12) was identical to part A except that clarithromycin (500 mg twice daily) was substituted for rifabutin.

RESULTS

In part A, fluconazole decreased the area under the plasma concentration-time curve (AUC), percent of dose excreted in 24-hour urine, and formation clearance (CL f ) of the hydroxylamine by 37%, 53%, and 61%, respectively (paired t test, P < .05). Rifabutin increased the AUC, percent excreted, and CL f of the hydroxylamine by 55%, 45%, and 53%, respectively ( P < .05). Fluconazole plus rifabutin decreased the AUC, percent excreted, and CL f of the hydroxylamine by 21%, 37%, and 46%, respectively ( P < .05). In part B the fluconazole data were similar to those of part A. Overall, clarithromycin had no effect on hydroxylamine production.

CONCLUSIONS

If the exposure (AUC) to sulfamethoxazole hydroxylamine is predictive of sulfamethoxazole toxicity, then rifabutin will increase and clarithromycin plus fluconazole or rifabutin plus fluconazole will decrease the rates of adverse reactions to sulfamethoxazole in HIV-infected subjects.

Simultaneous determination of sulfamethoxazole and trimethoprim in human plasma by capillary zone electrophoresis

A capillary electrophoretic method for the simultaneous determination of sulfamethoxazole and trimethoprim in plasma was developed. Sulfamethoxazole and trimethoprim extracted from human plasma with ethyl acetate were analyzed at 20 kV and 25 degrees C using 15 mm phosphate buffer (pH 6.2) as the electrolyte. The detection was by UV at 220 nm. The run time was 8.0 min and the limit of quantification was 10.00 microg/mL for sulfamethoxazole and 2.00 microg/mL for trimethoprim. The recovery was >99% for both compounds. This method enabled the detection of sulfamethoxazole and trimethoprim in plasma of patients after oral ingestion of their combined formulation. The present simple and rapid method is applicable to drug monitoring in immunocompromised patients who are taking the combined formulation of these compounds for the treatment or prophylaxis of Pneumocystis carinii pneumonia.

[A case of Nocardia farcinica pneumonia treated with sulfamethoxazole-trimethoprim monitoring its serum concentration]

A 75-year-old male suffered from interstitial pneumonia in December 2000 and treated with predonisolone. The treatment was effective, and the dosage of predonisolone had been gradually tapered. In January 2001, when the dosage was 30 mg/day, he complained of cough and yellowish sputum. The chest X-ray and CT revealed bilateral infiltrations with cavities. He was treated with cefozopram and fluconazole. However, there were no improvements. The sputa of the 2nd, 3rd, 6th and 8th hospital days showed the presence of gram-positive branched rods, which were identified as Nocardia farcinica. Therefore, the treatment was changed to sulfamethoxazole-trimethoprim. During the treatment, serum concentration of sulfamethoxazole was repeatedly measured, and kept over 60 microgram/ml. He was swiftly recovered after the start of sulfamethoxazole-trimethoprim. This case was supposed to be the seventh one of N. farcinica pneumonia in Japan, and the measurement of the concentration of sulfamethoxazole was useful to determine its dosage.

Circadian changes in pharmacokinetics of sulfamethoxazole administered orally to rabbits

Circadian variations of sulfamethoxazole pharmacokinetics were studied after a single oral administration of sulfamethoxazole, 50 mg/kg, to rabbits at 09:00 (a.m.) and 22:00 (p.m.). The profiles of plasma sulfamethoxazole concentration showed from 6 h to 24 h significant statistical difference (p<0.05) between 09:00 and 22:00. The half-life (t(1/2)) was significantly shorter in the morning (11.2 +/- 3.2 h) when compared to the nighttime (15.4 +/- 3.5 h) (p< 0.05). The AUC was significantly decreased in the morning (1325 +/- 264 microg/ml x h) than that in the nighttime (2059 +/- 379 microg/ml x h) (p<0.05). Total body clearance (CLt) was significantly higher when sulfamethoxazole was given in the morning (6.65 +/- 0.23 ml/min) versus in the nighttime (4.28 +/- 0.20 ml/min) (p<0.05).

Micellar electrokinetic capillary chromatography as a powerful tool for pharmacological investigations without sample pretreatment: a precise technique providing cost advantages and limits of detection to the low nanomolar range

A number of pharmaceuticals (e.g., acetaminophen, salicylic acid, sulfamethoxazole, theophylline, tolbutamide and trimethoprim) have been determined in human plasma by micellar electrokinetic chromatography (MEKC), without sample pretreatment, using underivatized fused-silica capillaries. The total analysis time was only 10 min. A sodium dodecyl sulfate (SDS)-containing borate buffer (60 mM with 200 mM SDS) at pH 10 was used. Between runs, proteins adsorbed to the capillary wall are removed by rinsing with SDS buffer and either acetonitrile (e.g., 50% v/v) or isopropanol (e.g., 10% v/v). Other rinsing procedures are discussed (salts, enzyme-containing solutions, organic solvents, sodium hydroxide, hydrofluoric acid). The separation system is tested in a concentration range between 10 ng/mL and 100 microg/mL; a detection limit of about 20 ng/mL can readily be obtained. The sensitivity was substantially improved using isopropanol as buffer additive. A day-to-day precision for relative peak areas of 1-2% relative standard deviation (RSD, n > 40) was reached in the upper concentration range. Under repeatability conditions, these values could also be obtained for low microg/mL concentrations. Thus, not only drug monitoring but also pharmacokinetic investigations from blood plasma become possible without further sample pretreatment.

Pharmacokinetic investigations with direct injection of plasma samples: possible savings using capillary electrophoresis (CE)

Capillary electrophoresis (CE) is often regarded as a separation technique of choice because of its high selectivity and its cost advantages compared to LC.RSD% of 0.5% have become standard for quality control assays. Using CE, sample pretreatment can often be significantly reduced, leading to notable savings of labor and reagent costs. Moreover, errors from sample pretreatment steps are avoided. A number of pharmaceuticals (e.g. acetaminophen, salicylic acid, sulfamethoxazole, theophylline, tolbutamide, and trimethoprim) have been determined in human plasma on underivatized fused silica capillaries by MEKC without sample pretreatment, the total analysis time being only 10 min. An sodium dodecyl sulfate-containing borate buffer (60 mM with 200 mM SDS) at pH 10 has been used. Between runs, proteins adsorbed to the capillary wall are removed by a rinsing regimen consisting of SDS buffer and either acetonitrile (e.g. 50% v/v) or isopropanol (e.g. 10% v/v). Other rinsing approaches are discussed (salts, enzyme containing solutions, organic solvents, sodium hydroxide, hydrofluoric acid). The separation system is tested in a concentration range between 10 ng/mL and 100 micrograms/mL, the detection limit being about 5 ng/mL. The sensitivity has been substantially improved compared to preceding work using field-amplified injection mechanisms and efficient computer algorithms that take advantage of multiwavelength detection. Correlations between the limit of quantitation (LOQ), the limit of detection (LOD) and the signal/noise ratio are discussed. A day-to-day precision for relative peak areas of 1 to 2% relsdv (n > 40) has been reached in the upper concentration range. Thus, not only drug monitoring but also pharmacokinetic investigations from blood plasma have become possible without further sample pretreatment.

Therapeutic failure of trimethoprim/sulfamethoxazole in the treatment of Pneumocystis carinii pneumonia

OBJECTIVE

To report a case of failure of treatment of Pneumocystis carinii pneumonia (PCP) with trimethoprim/sulfamethoxazole (TMP/SMX) in a patient with HIV infection, despite an adequate serum SMX concentration.

CASE SUMMARY

A 52-year-old white man was treated with TMP/SMX for PCP. After discharge he returned to the hospital with worsening of the PCP despite a serum SMX concentration of 60 micrograms/mL 18 hours after his last dose of TMP/SMX.

DISCUSSION

PCP is one of the most common complications of HIV infection. TMP/SMX is the drug of choice for prophylaxis and treatment. The causes of therapeutic failure with this agent are not well documented.

CONCLUSIONS

Alternative therapies to TMP/SMX should be seriously considered if the serum concentrations are therapeutic and the patient is not clinically improved.

Comparative pharmacokinetics and bioavailability of two cotrimoxazole preparations

The objective of this study was to assess both pharmacokinetic properties and bioavailability of a newly developed cotrimoxazole preparation (Bioprim tablets, 80 mg of trimethoprim/400 mg sulfamethoxazole), in comparison with a reference preparation commercially available (Bactrim tablets, 80 mg of trimethoprim/400 mg of sulfamethoxazole). The pharmacokinetics and bioavailability of cotrimoxazole from these preparations were compared in an open randomized crossover study in 12 healthy males. Plasma concentrations of trimethoprim and sulfamethoxazole were measured by HPLC after protein precipitation. Noncompartmental pharmacokinetic analysis was performed on the plasma concentration-time data. The obtained pharmacokinetic values (Cmax, tmax, beta, t1/2 beta, CL, Vd, AUC36, AUC infinity) of both trimethoprim and sulfamethoxazole determined in our study agreed with values reported in the literature. Westlake's and Nonparametric probability tests with the 90% confidence intervals, for both trimethoprim and sulfamethoxazole gave the differences within 80 and 120%, for all necessary measures (Cmax, tmax and AUC infinity). Statistical analysis of the data has shown that the preparations have similar pharmacokinetic profiles and therefore can be considered equally bioavailable.

Determination of pharmaceuticals in plasma by capillary electrophoresis without sample pretreatment reproducibility, limit of quantitation and limit of detection

Pharmaceuticals in human plasma are determined on underivatized fused-silica capillaries by micellar electrokinetic capillary chromatography (MEKC) without sample pretreatment. Our best method to date uses as running buffer a sodium dodecyl sulfate (SDS) containing borate buffer (60 mM with 200 mM SDS) at pH 10. Between runs, proteins adsorbed to the capillary wall are removed by an acetonitrile and SDS-buffer rinsing regimen (50% v/v each). A day-to-day precision for relative peak areas of about 2% relative standard deviation (RSD; n > 40) has been reached. Different rinsing approaches are discussed (salts, enzyme-containing solutions, organic solvents, hydrofluoric acid). The separation system is tested in a concentration range between approximately 100 mg/L-10 mg/L. Correlations between the limit of quantitation, the limit of detection and the signal/noise are discussed. The applicability of the system is demonstrated for the pharmaceuticals acetaminophen, salicylic acid, sulfamethoxazole, tolbutamide, and trimethoprim.

Quantitation of acetaminophen and salicylic acid in plasma using capillary electrophoresis without sample pretreatment. Improvement of precision

Capillary electrophoresis has become one of the most attractive techniques in the analysis of biological samples. Pharmaceuticals in human plasma can easily be determined on uncoated fused-silica capillaries without any sample pretreatment. Intra- and inter-day precision values of about 1-2% R.S.D. (n = 20) and 2-3% R.S.D. (n > 80) respectively are obtained using a sodium dodecyl sulfate-containing borate buffer, pH 10 and acetonitrile as a between-run rinsing reagent. This method is highly robust, no breakdowns of the current or capillary blockings were observed for several weeks. The general applicability is demonstrated for several model drugs. The effectiveness of other rinsing procedures including enzyme-containing solutions, different organic solvents and hydrofluoric acid is discussed.

The disposition of five therapeutically important antimicrobial agents in llamas

The disposition of five therapeutic antimicrobial agents was studied in llamas (Lama glama) following intravenous bolus administration. Six llamas were each given ampicillin, tobramycin, trimethoprim, sulfamethoxazole, enrofloxacin and ceftiofur at a dose of 12 mg/kg, 1 mg/kg, 3 mg/kg, 15 mg/kg, 5 mg/kg, and 2.2 mg/kg of body weight, respectively, with a wash out period of at least 3 days between treatments. Plasma concentrations of these antimicrobial agents over 12 h following i.v. bolus dosing were determined by reverse phase HPLC. Disposition of the five antimicrobial agents was described by a two compartment open model with elimination from the central compartment, and also by non-compartmental methods. From compartmental analysis, the elimination rate constant, half-life, and apparent volume of distribution in the central compartment were determined. Statistical moment theory was used to determine noncompartmental pharmacokinetic parameters of mean residence time, clearance, and volume of distribution at steady state. Based on the disposition parameters determined, and stated assumptions of likely effective minimum inhibitory concentrations (MIC) a dose and dosing interval for each of five antimicrobial agents were suggested as 6 mg/kg every 12 h for ampicillin; 4 mg/kg once a day or 0.75 mg/kg every 8 h for tobramycin; 3.0 mg/kg/15 mg/kg every 12 h for trimethoprim/sulfamethoxazole; 5 mg/kg every 12 h for enrofloxacin; and 2.2 mg/kg every 12 h for ceftiofur sodium for llamas. Steady-state peak and trough plasma concentrations were also predicted for the drugs in this study for llamas.

Oral bioavailability of sulphonamides in ruminants: a comparison between sulphamethoxazole, sulphatroxazole, and sulphamerazine, using the dwarf goat as animal model

The various sulphonamides show marked differences in disposition characteristics after administration to ruminants. For use in combination with a diaminopyrimidine derivative such as trimethoprim or baquiloprim, it is essential that a sulphonamide has similar pharmacokinetic properties in order to obtain optimal synergy. In the present study the pharmacokinetics of sulphamethoxazole, sulphatroxazole, and sulphamerazine were investigated in dwarf goats (n = 6) after IV and intraruminal administration at a dose of 30 mg/kg bodyweight. In addition, the in vitro binding of sulphamerazine to ruminal contents was studied as a possible explanation for a reduced absorption rate. Sulphamethoxazole showed the most rapid absorption after intraruminal administration (mean tmax +/- SD : 0.8 +/- 0.2h). However, the drug was rapidly eliminated from the plasma (t1/2 beta : 2.4 +/- 1.5 h) and the bioavailability was only 12.4 +/- 4.7%, most likely due to an extensive 'first-pass' effect. The bioavailability of orally administered sulphamerazine and sulphatroxazole was much higher (67.6 +/- 13.5% and 70.2 +/- 32.3%, respectively). After intraruminal administration, sulphatroxazole showed the highest plasma peak concentration (26.1 +/- 6.3 mg/l) and the longest plasma half-life (4.7 +/- 1.8h) and mean residence time (13.9 +/- 4.5 h). Sulphamerazine showed considerable binding to rumen contents in vitro. Based on its pharmacokinetic properties sulphatroxazole appears to be a suitable candidate to be used in combination with the more recently developed diaminopyrimidines such as baquiloprim.

High-performance liquid chromatographic evaluation of the effect of heat treatment on trimethoprim and sulfamethoxazole stability in serum

Heat treatment of patient samples is utilized as a method to decrease the risk of accidental transmission of human immunodeficiency virus (HIV). Heat treatment has been reported to affect the outcome of drug analysis. In this study, the effects of heat treatment (56 degrees C for 5 h) and storage for 2 months at -20 degrees C on the stability of trimethoprim (TMP) and sulfamethoxazole (SMX) at three different concentrations in serum (10/100, 1/20, and 0.1/5 microgram/mL) each were evaluated. Simultaneous determination of TMP, SMX, and sulfamethazine (SMeth), the internal standard, in serum was performed by a reversed-phase high-performance liquid chromatographic (HPLC) procedure with isocratic elution and ultraviolet detection. The peak/height ratios (PHRs) for each sample from untreated and heat-treated groups were compared. No statistically significant differences were found between untreated and heat-treated groups for TMP. Heat treatment decreased the PHR for SMX at 100 micrograms/ml concentration (p = 0.042) and increased the PHR for SMX at 20 micrograms/ml concentration (p = 0.049). These marginal differences are unlikely to be significant. Storage of samples for 2 months at -20 degrees C had no statistically significant effect on sample PHRs. Thus, heat treatment of serum does not alter clinical interpretation of TMP and SMX at clinically relevant concentrations and may protect laboratory workers from accidental HIV exposure.

Immune response to sulfamethoxazole in patients with AIDS

Antibody- and cell-mediated responses to sulfamethoxazole (SMX) were analyzed in AIDS patients with or without a history of hypersensitivity and in negative controls. In 20 of 20 (P < 0.01) human immunodeficiency virus (HIV)-seropositive patients with skin reactions to cotrimoxazole, we found SMX-specific antibodies, while only 9 of 20 and 17 of 20 HIV-seropositive patients without a history of hypersensitivity to cotrimoxazole had SMX-specific immunoglobulin M (IgM) and IgG, respectively. The levels of specific IgM and IgG were higher in patients with skin reactions than in patients without reactions (IgM, 1.0 +/- 0.19 versus 0.47 +/- 0.23 [P < 0.001]; IgG, 0.68 +/- 0.15 versus 0.47 +/- 0.14 [P < 0.001] [mean optical density values +/- standard deviations]). Seronegative controls with no history of exposure to sulfa compounds did not have SMX-specific IgG or IgM antibodies, and controls with a history of intake of SMX with or without reactions had low levels of IgG and IgM. The SMX-specific IgG subclasses were exclusively IgG1 and IgG3. None of the patients had detectable SMX-specific IgE or IgA antibodies nor did they exhibit a cell-mediated response as measured by a lymphocyte proliferation assay. Antibodies to SMX recognized N-acetyl-sulfonamide, N-(2-thiazolyl)-sulfanilamide, sulfadiazine, and sulfisoxazole but did not recognize sulfanilamide or 3-amino-5-methyl isoxazole in an inhibition assay. It is not known whether the SMX-specific antibodies associated with hypersensitivity reactions to SMX in HIV-seropositive patients have a pathogenic role in these reactions. Sulfanilamide or 3-amino-5-methyl isoxazole, on the other hand, could be potential alternative therapies in HIV-seropositive patients with a history of skin reactions to SMX.

Simultaneous determination of ormethoprim and sulphadimethoxine in plasma and muscle of Atlantic salmon (Salmo salar)

A rapid clean-up and high-performance liquid chromatographic method for the simultaneous determination of ormethoprim and sulphadimethoxine in plasma and muscle of Atlantic salmon (Salmo salar) has been developed. Sample preparation is based on protein precipitation using trichloroacetic acid or methanol for plasma and muscle, respectively. The drugs are separated using a reversed-phase C18 analytical column and phosphate buffer-acetonitrile (80:20, v/v) containing 1-heptanesodiumsulphonate and triethylamine, as mobile phase. Detection was performed at 270 nm. The average recovery of ormethoprim was 97.2% in muscle and 95.7% in plasma, whereas the average recovery of sulphadimethoxine was 86.5% in muscle and 90.2% in plasma. The limit of detection at a signal-to-noise ratio of 3 was 50 ng/g and 30 ng/ml for ormethoprim in muscle and plasma respectively and 30 ng/g and 15 ng/ml in muscle and plasma respectively for sulphadimethoxine.

Pharmacokinetics of sulphamethoxazole and trimethoprim administered intravenously and orally to Japanese quails

The pharmacokinetic behaviour of sulphamethoxazole and trimethoprim was studied after combined intravenous (i.v.) administration at doses of 20 mg/kg and 4 mg/kg, respectively, and after oral administration at doses of 50 mg/kg and 10 mg/kg. The serum concentration versus time data after i.v. administration were best described by the biexponential equations C = 34.77.e-2.655.t + 39.03.e-0.241.t for sulphamethoxazole and C = 3.29.e-3.878.t + 0.83.e-0.306.t for trimethoprim. Mean biological half-lives of the drugs were 2.89 +/- 0.11 and 2.38 +/- 0.33 h, respectively. The distribution volumes (V area) were 0.475 +/- 0.026 l/kg (sulphamethoxazole) and 3.89 +/- 0.61 l/kg (trimethoprim). Orally administered sulphamethoxazole and trimethoprim were rapidly absorbed. The maximum serum concentrations were reached 0.5-1 h after administration. The bioavailability was 81% for sulphamethoxazole and 41% for trimethoprim.

Formation and elimination of sulphamethoxazole hydroxylamine after oral administration of sulphamethoxazole

The formation and elimination of sulphamethoxazole hydroxylamine in relation to the pharmacokinetics of the parent compound and its N4-acetyl metabolite were investigated in six healthy subjects after a single oral dose of 800 mg sulphamethoxazole. The apparent half-lives of sulphamethoxazole and its metabolites were approximately 10 h, indicative of formation rate-limited metabolism. The mean residence time of the hydroxylamine metabolite was 5.5 +/- 1.5 h. The renal clearance of sulphamethoxazole hydroxylamine was 4.39 +/- 0.91 l h-1. The urinary recovery of sulphamethoxazole accounted for 16.5 +/- 5.5% of the dose, N4-acetyl-sulphamethoxazole for 46.2 +/- 6.6% and the hydroxylamine metabolite for 2.4 +/- 0.8%. The remaining 35% of the dose was unaccounted for. Acetylator phenotype was determined using sulphadimidine. The renal excretion of sulphamethoxazole hydroxylamine was 1.9 +/- 0.9% in slow acetylators (n = 3) and 2.8 +/- 0.3% in fast acetylators (n = 3); for N4-acetyl-sulphamethoxazole the values were 48 +/- 6% and 44 +/- 8%, respectively. Sulphamethoxazole is metabolized, although to a limited extent, to a hydroxylamine metabolite. This metabolite may be important for the pathogenesis of adverse reactions.

The activity of PS-15 in combination with sulfamethoxazole

PS-15 is a novel biguanide folate antagonist that is metabolized in vivo to WR99210, a metabolite that is extremely active in vitro against multi-drug resistant strains of Plasmodium falciparum. When PS-15 was administered in combination with sulfamethoxazole to healthy Saimiri sciureus monkeys, the serum antimalarial activity was considerably greater than that observed in monkeys that received PS-15 alone. Further studies should be carried out to determine the value of PS-15/sulfonamide combinations in the treatment of human malaria infections and in preventing the emergence of drug-resistant parasites.

Disposition of drugs in cystic fibrosis. VII. Acetylation of sulfamethoxazole in blood cells: in vitro-in vivo correlation and characterization of its kinetics of acetylation in lymphocytes

OBJECTIVE

To determine if acetylation of sulfamethoxazole in blood cells is a surrogate measure of its acetylation in vivo. If it is, to use these cells to determine the mechanism(s) by which acetylation of sulfamethoxazole is enhanced in cystic fibrosis.

METHODS

Single-point sulfamethoxazole acetylation activity in blood cells obtained from patients with cystic fibrosis (n = 6) and control subjects (n = 7) who had previously participated in our in vivo study was determined. The parameters, Vmax and Km, for acetylation of sulfamethoxazole in lysed lymphocytes obtained from patients with cystic fibrosis (n = 6) and control subjects (n = 5) were also determined.

RESULTS

The acetylation activity in cystic fibrosis whole blood, lysed erythrocytes, and lysed peripheral blood mononuclear cells was significantly (p < 0.05) greater than that in cells obtained from control subjects and was highly correlated with acetylation of sulfamethoxazole in vivo (r > 0.80). The apparent Vmax for cystic fibrosis lymphocyte lysate was significantly (p < 0.05) greater than that obtained for control lymphocyte lysate (72.99 +/- 9.07 versus 60.97 +/- 2.26 pmol/mg protein/min), and the apparent Km was significantly (p < 0.05) lower (0.51 +/- 0.07 versus 0.73 +/- 0.06 mmol/L).

CONCLUSION

Blood cells may be used as surrogate markers to elucidate the mechanism(s) by which acetylation of sulfamethoxazole (catalyzed by the monomorphic N-acetyltransferase) is enhanced in subjects with cystic fibrosis. Both activation or activation and induction of the monomorphic N-acetyltransferase should be considered as possible mechanism(s) to explain this phenomenon.

Assay of the acetyl-CoA probe acetyl-sulfamethoxazole and of sulfamethoxazole by gas chromatography-mass spectrometry

We present gas chromatographic-mass spectrometric assays for (i) the concentration of sulfamethoxazole and (ii) the concentration and molar percentage enrichment of acetyl-sulfamethoxazole in biological fluids. The compounds are extracted with ethyl acetate, derivatized with either diazomethane or pentafluorobenzyl bromide, and analyzed by gas chromatography-mass spectrometry. Quantitation is achieved using internal standards, [2H4]sulfamethoxazole and acetyl-[2H4]sulfamethoxazole. Limits of detection are 200 nmol for the methyl derivatives and 2 nmol for the pentafluorobenzyl derivatives. The high sensitivity of the assay with the pentafluorobenzyl derivatives allows measuring in plasma and urine (i) the pharmacokinetics of sulfamethoxazole and acetyl-sulfamethoxazole and (ii) the stable isotope enrichment of the acetyl moiety of acetyl-sulfamethoxazole. The latter is used as a probe for the noninvasive chemical biopsy of liver extramitochondrial acetyl-CoA.

Variability of serum concentrations of trimethoprim and sulfamethoxazole during high dose therapy

Serum kinetics of trimethoprim and sulfamethoxazole were studied in 23 patients during oral and i.v. treatment of Pneumocystis carinii pneumonia. Daily doses of 15-22 mg/kg trimethoprim and 75-110 mg/kg sulfamethoxazole were given every 6 h. Despite administration of a loading dose of twice the regular dose, serum trough concentrations continuously rose from 12 h to 96 h by 63% for trimethoprim and 102% for sulfamethoxazole. After 4-6 days mean trough concentrations of trimethoprim and sulfamethoxazole were 7.7 +/- 3.0 and 198 +/- 74 mg/l, with individual values of < 4.6 and < 103 mg/l in two patients and > 11.4 and > 307 mg/l in two others. Patients treated orally or i.v. had similar serum levels. However, large interindividual variability was observed despite weight-specific dosing. Administration of a loading dose did not prevent accumulation of serum levels of trimethoprim and sulfamethoxazole over several days of treatment.

Multiple-dose pharmacokinetics of 12 milligrams of trimethoprim and 60 milligrams of sulfamethoxazole per kilogram of body weight per day in healthy volunteers

The disposition of 12 mg of trimethoprim and 60 mg of sulfamethoxazole per kg of body weight in six healthy male volunteers is described. The daily dose was evenly divided and administered orally every 6 h for 13 consecutive doses. Individual drug components were assayed by high-performance liquid chromatography. Steady-state concentrations in serum for trimethoprim and sulfamethoxazole were within the purported therapeutic ranges for treating Pneumocystis carinii pneumonia. Co-trimoxazole was well tolerated, and no subject withdrew from the study because of toxicity. Comparison of the pharmacokinetic parameters in this study with those of our previous findings indicates that the elimination of trimethoprim-sulfamethoxazole follows a first-order process within the dose ranges assessed. Administration of 15- to 20-mg/kg trimethoprim and 75- to 100-mg/kg sulfamethoxazole in four evenly divided doses for the first 24 h followed by 12 and 60 mg/kg/day, respectively, for the remainder of therapy rapidly attains concentrations in serum within the proposed P. carinii pneumonia therapeutic range. Clinical trials are indicated to evaluate this dosing scheme, which may decrease exposure to potentially excessive concentrations of trimethoprim and sulfamethoxazole.

Use of low-dose trimethoprim-sulfamethoxazole thrice weekly for primary and secondary prophylaxis of Pneumocystis carinii pneumonia in human immunodeficiency virus-infected patients

We conducted an open prospective clinical trial to evaluate the efficacy and toxicity of trimethoprim-sulfamethoxazole given as one double-strength tablet thrice weekly for primary and secondary prophylaxis of Pneumocystis carinii pneumonia (PCP) in human immunodeficiency virus-infected (HIV+) patients. A total of 104 HIV+ patients were evaluated, with 74 being in the primary prophylaxis group and 30 being in the secondary prophylaxis group. All except six patients received concomitant zidovudine; five patients on primary prophylaxis and one patient on secondary prophylaxis refused zidovudine. There were 70 patients evaluated for the efficacy of primary prophylaxis. The mean CD4 count was 124.4 +/- 110.1 cells per microliter. The mean follow-up time was 11.8 +/- 5.8 months (median, 12 months; range, 1 to 32 months). Two noncompliant patients developed PCP after 1 and 3 months of chemoprophylaxis. The failure rate (under the intention to treat principle) was 2 of 70 patients (2.9%; 95% confidence interval, 0.35 to 10%), or 1 per 413 patient-months of observation. There were 27 patients evaluated for the efficacy of secondary prophylaxis. The mean follow-up time was 12.4 +/- 7.2 months (median, 11 months; range, 1 to 29 months). Two patients, one of whom was noncompliant, were treatment failures, developing PCP after 14 and 15 months of chemoprophylaxis; this gave a failure rate of 2 of 27 patients (7.4%; 95% confidence interval, 0.9 to 24.3%), or 1 per 167 patient-months of observation. Adverse reactions sufficient to permanently terminate therapy occurred in 9 of 104 patients (8.7%; 95% confidence interval, 4 to 15.7%) overall. The serum trimethoprim, sulfamethoxazole, and N4-acetyl-sulfamethoxazole concentrations measured by high-pressure liquid chromatography were uniformly low. One double-strength tablet of trimethoprim-sulfamethoxazole taken weekly on Monday, Wednesday, and Friday appeared to be well tolerated and efficacious for the prophylaxis of PCP in HIV+ patients at high risk and deserves further investigation.

Pharmacokinetics and adverse effects of 20-mg/kg/day trimethoprim and 100-mg/kg/day sulfamethoxazole in healthy adult subjects

The pharmacokinetics of trimethoprim-sulfamethoxazole were studied in 12 healthy adult subjects receiving trimethoprim at 20 mg/kg of body weight per day and sulfamethoxazole at 100 mg/kg/day, which is the conventional dose for treating Pneumocystis carinii pneumonia (PCP). Daily doses were evenly divided and orally administered every 6 h for 3 days. Trimethoprim, sulfamethoxazole, and N4-acetylsulfamethoxazole concentrations in serum and urine were measured by high-performance liquid chromatography. Five subjects withdrew from the study because of intolerable gastrointestinal and central nervous system toxicities. In the seven subjects that completed the study, the mean maximum serum drug concentrations after the last dose were 13.6 +/- 2.0, 372 +/- 64, and 50.1 +/- 10.9 micrograms/ml for trimethoprim, sulfamethoxazole, and N4-acetylsulfamethoxazole, respectively. The mean half-lives were 13.6 +/- 3.5, 14.0 +/- 2.3, and 18.6 +/- 4.3 h, respectively. Changes in absolute neutrophil count were significantly correlated with the minimum concentrations of trimethoprim and sulfamethoxazole in serum and trimethoprim area under the concentration-time curve (for all three parameters, r2 = 0.6 and P less than 0.05). Our findings add to the evidence that serum drug concentrations in adults following the conventional dose of trimethoprim-sulfamethoxazole for PCP are excessive and contribute to certain adverse reactions. Further studies are indicated in patients to optimize the dosing regimen of trimethoprim-sulfamethoxazole in the treatment of PCP.

Disposition of drugs in cystic fibrosis. I. Sulfamethoxazole and trimethoprim

The disposition of sulfamethoxazole and trimethoprim, after constant rate intravenous administration (10 mg/kg/hr sulfamethoxazole and 2 mg/kg/hr trimethoprim for 1 hour), was investigated in adult patients with cystic fibrosis (n = 7) and in age-matched healthy subjects (control subjects, n = 8). The total plasma clearance of sulfamethoxazole was found to be increased in cystic fibrosis (0.0262 +/- 0.0064 L/hr/kg) when compared with that found in control subjects (0.0188 +/- 0.0043 L/hr/kg). This increase in clearance was found to be primarily attributable to an increase in the metabolic clearance of sulfamethoxazole to N4-acetylsulfamethoxazole (0.00903 +/- 0.00247 versus 0.00355 +/- 0.00049 L/hr/kg) with the renal clearance of sulfamethoxazole remaining unchanged. These conclusions were not altered when the pharmacokinetic parameters were computed for the unbound drug or when they were normalized with respect to body surface area. These data indicate that, in cystic fibrosis, the enzymes mediating the metabolism of sulfamethoxazole to N4-acetylsulfamethoxazole, N-acetyltransferase(s), may be induced, activated, or both, or that the uptake of sulfamethoxazole by cells that metabolize sulfamethoxazole to N4-acetylsulfamethoxazole is enhanced. The total plasma clearance of trimethoprim was also found to be increased in cystic fibrosis (0.1808 +/- 0.0440 L/hr/kg) when compared with that found in control subjects (0.1139 +/- 0.0193 L/hr/kg). In contrast to sulfamethoxazole, this increase in clearance was found to be primarily attributable to an increase in the renal clearance of trimethoprim (0.1240 +/- 0.0299 versus 0.0720 +/- 0.0166 L/hr/kg). These data indicate that the tubular secretion of trimethoprim may be enhanced in cystic fibrosis.

Trimethoprim and sulfamethoxazole transfer in the in vitro perfused human cotyledon

Utilizing the in vitro human placental model, we studied the placental transfer of trimethoprim and sulfamethoxazole. At trimethoprim concentrations of 7.2 micrograms/ml, only 1.4 micrograms/ml was transported across the placenta after 1 h, and at concentrations of 1.0 microgram/ml, one half the usual serum level, only 0.08 microgram/ml was transported across the placenta. Maternal concentrations of sulfamethoxazole of 29.6 and 127.7 micrograms/ml resulted in concentrations of 5.1 and 14.8 micrograms/ml on the fetal side, respectively. Thus, it would appear that trimethoprim is slowly transported across the placenta and in low concentrations whereas sulfamethoxazole readily crosses the placenta. The combination of these drugs is useful for treatment of bacteriuria. It may also prove to be especially useful for Pneumocystis carinii infections in pregnant women with AIDS. With a half-life of 13 h for trimethoprim and 6 h for sulfamethoxazole, the drugs are not likely to achieve toxic levels in the fetal compartment. Thus, it would appear that trimethoprim and sulfamethoxazole may be both efficacious and safe for the treatment of both these infections during pregnancy.

Pharmacokinetics of sulfamethoxazole and trimethoprim in Mexicans: bioequivalence of two oral formulations (URO-TS D and Bactrim F)

Two oral pharmaceutical formulations (URO-TS D and Bactrim F) containing 800 mg of sulfamethoxazole (SMZ) and 160 mg of trimethoprim (TMP) were given to 10 Mexican healthy volunteers, following a randomized cross-over design. Blood and urine samples were obtained, concentrations of TMP, SMZ, and its metabolite N4-acetyl SMZ were measured by HPLC and pharmacokinetic analyses were performed. The observed Cmax, tmax, half-life, AUC, and cumulative urinary excretion values for the three compounds studied were within the ranges that have been previously reported for European and North American subjects. Therefore, it appears that pharmacokinetics of SMZ and TMP in Mexicans are similar to those observed in Caucasian populations. When the two studied formulations were compared, no statistically significant differences were detected in any pharmacokinetic parameter. Therefore, it is concluded that both brands tested are bioequivalent. Moreover, these two formulations manufactured in Mexico yield SMZ and TMP plasma and urine levels similar to those obtained with equivalent formulations of European or North American origin.

[Study of the in vivo penetration of cotrimoxazole in alveolar macrophages]

Kinetic of cotrimoxazole was studied in serum, alveolar macrophages and BAL fluid from guinea pigs receiving sulfamethoxazole (SMX, 100 mg/kg) and trimethoprim (TMP, 20 mg/kg). Guinea pigs were killed by cervical dislocation 30 min, 1 h, 3 h, 6 h and 24 h after intraperitoneal injection. Lung lavage was performed to obtain alveolar macrophages and BAL fluid. TMP and SMX levels were assayed using high-performance-liquid chromatography. Highest SMX levels were obtained in serum at 30 min, in BAL fluid at 1 h and in alveolar macrophages at 3 h. Mean SMX/TMP ratios (30 min, 1 h, 3 h) was 26.5 +/- 0.8 in serum, 3.76 +/- 1.8 in BAL fluid and 1.15 +/- 0.02 in alveolar macrophages.

Concentrations of trimethoprim and sulfamethoxazole in cerebrospinal fluid and serum in mares with and without a dimethyl sulfoxide pretreatment

Each of seven mares was given an intravenous (IV) injection of 40% dimethyl sulfoxide (DMSO) at a dosage of 1 g/kg, over 35 min, immediately followed by a single IV injection of a trimethoprim (TMP) and sulfamethoxazole (SMZ) combination (SMZ 83%, TMP 17%) at a combined dosage of 44 mg/kg (7.48 mg/kg TMP; 36.52 mg/kg SMZ). Each horse served as its own control and was alternately treated with an identical dose of TMP-SMZ treatment alone at least seven days following or preceding the DMSO and TMP-SMZ treatment. Serum and cerebrospinal fluid (CSF) concentrations of TMP and SMZ were measured over a six hour period. Dimethyl sulfoxide treatment caused no significant difference in the mean serum concentration of SMZ or in the mean CSF concentrations of TMP or SMZ. The mean serum concentration of TMP was significantly (p less than 0.05) increased at the two, four and six hour sampling time in the mares receiving pretreatment with DMSO. The clearance of TMP was also significantly (p less than 0.05) decreased from 675 mL/h/kg to 327 mL/h/kg by DMSO administration. Concentrations of TMP and SMZ in the CSF in both treatment groups exceeded the minimum inhibitory concentrations for many common bacterial pathogens of equine origin. In addition, CSF concentration of TMP exceeded the serum concentrations required for 50% inhibition of dihydrofolate reductases of protozoan origin. Serum TMP and SMZ concentration were similar to those reported to be effective against Toxoplasma gondii in in vitro studies on the killing or inhibition of the organism.

Sulphamethoxazole acetylation in fast and slow acetylators

Acetylation of sulphamethoxazole was studied in 22 subjects previously phenotyped with sulphadimidine. Sulphamethoxazole and its acetylated metabolite were measured in 6 h plasma and 0-6 h urine samples. Percentage of plasma acetylated-sulphamethoxazole did not correlate with the percentage of urinary acetylated-sulphamethoxazole. There was also no correlation between the percentage of acetylated-sulphadimidine and percentage of acetylated-sulphamethoxazole in plasma. The finding suggest that the acetylation of sulphamethoxazole has no predictive value in determining acetylator status.

Renal selective N-acetyl-gamma-glutamyl prodrugs. II. Carrier-mediated transport and intracellular conversion as determinants in the renal selectivity of N-acetyl-gamma-glutamyl sulfamethoxazole

The mechanism of activation of the prodrug N-acetyl-L-gamma-glutamyl sulfamethoxazole (AGSM) and of gamma-glutamyl sulfamethoxazole (GSM) as a model for the mechanism of the renal selectivity of N-acetyl-gamma-glutamyl prodrugs was investigated. The hypothesis was tested that this selectivity is due largely to a carrier-mediated transport followed by an intracellular conversion of the prodrug to the active drug, in contrast to another mechanism. The transport of AGSM and GSM was studied with the use of kidney slices. AGSM accumulated in the slices. At 75 microM substrate concentration, the slice to medium ratio was 2.5 +/- 0.2. This accumulation was inhibited by the anion transport inhibitor probenecid (82% inhibition at 1.0 mM) and by the gamma-glutamyl transport inhibitor buthionine sulfoximine (60% at 1.0 mM). Acivicin, L-(alpha S,5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazole acetic acid did not inhibit AGSM accumulation at 0.1 mM, a concentration sufficient to inhibit the enzyme gamma-glutamyl transpeptidase; at 1.0 mM, however, AGSM accumulation was inhibited by 44%. These results suggest that the accumulation of AGSM is caused by an active transport process. GSM did not accumulate in the slices, but was completely converted to sulfamethoxazole (SM) after a 90-min incubation. Accumulation of AGSM was also seen in vivo: at 20 min after AGSM administration (10 mg.kg-1) the plasma, kidney and liver concentrations were 73 +/- 6, 110 +/- 7 and 37 +/- 5 micrograms.g-1, respectively. This accumulation could be inhibited by buthionine sulfoximine but not by acivicin.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of trimethoprim-sulphamethoxazole in two-day-old foals after a single intravenous injection

Six healthy two-day-old foals (3 pony foals and 3 horse foals) were given a single intravenous (iv) injection of trimethoprim (TMP)--sulphamethoxazole (SMZ) at a dosage of 2.5 mg of TMP/kg bodyweight (bwt) and 12.5 mg of SMZ/kg bwt. Serum TMP and SMZ concentrations were measured serially during a 24 hour period. The overall elimination rate constant (K) for TMP in the pony and horse foals was 0.45/h, whereas the K values for SMZ for the pony and horse foals were 0.12/h and 0.07/h, respectively (no significant difference; P greater than 0.05). Based on published minimum inhibitory concentration values for equine pathogens (Adamson et al 1985), the primary indication for the use of TMP/SMZ in foals may be in the treatment of infections caused by gram-positive bacteria. A dosage of 2.5 mg of TMP/kg bwt and 12.5 mg of SMZ/kg bwt, given iv at 12 h intervals would be appropriate.

Dapsone, trimethoprim, and sulfamethoxazole plasma levels during treatment of Pneumocystis pneumonia in patients with the acquired immunodeficiency syndrome (AIDS). Evidence of drug interactions

STUDY OBJECTIVE

To examine the interaction between dapsone and trimethoprim in patients with the acquired immunodeficiency syndrome (AIDS).

DESIGN

Measurement of drug levels as part of an open study of dapsone alone and randomized, double-blind comparison of trimethoprim-dapsone with trimethoprim-sulfamethoxazole in treating Pneumocystis carinii pneumonia in patients with AIDS.

SETTING

County hospital and AIDS clinic.

PATIENTS

Eighteen patients treated with dapsone alone, 30 with trimethoprim-dapsone, and 30 with trimethoprim-sulfamethoxazole.

INTERVENTION

Dapsone, 100 mg/d; trimethoprim, 20 mg/kg body weight per day, and sulfamethoxazole, 100 mg/kg.d; administered for 21 days.

MEASUREMENTS AND MAIN RESULTS

Concentrations of dapsone were 40% higher in patients treated with trimethoprim-dapsone than in those treated with dapsone alone (2.1 compared with 1.5 micrograms/mL; P less than 0.05). Trimethoprimdapsone-treated patients had fewer treatment failures but more side effects and treatment terminations due to toxicity than those treated with dapsone alone. The concentration of trimethoprim was 48.4% higher in patients treated with trimethoprim-dapsone than in those treated with trimethoprim-sulfamethoxazole, (18.4 compared with 12.4 micrograms/mL; P less than 0.05). Discontinuation of therapy due to toxicity was commoner in the trimethoprim-sulfamethoxazole group (57% compared with 30%).

CONCLUSIONS

A bidirectional drug interaction exists between dapsone and trimethoprim, resulting in higher concentrations of each in the presence of the other.

[Nocardial brain abscess: case report]

A 25-year-old man, who was slightly immunosuppressed, presented headache and right motor weakness due to multiple brain abscesses disseminated from lung abscess. They were diagnosed, by bacteriological examination, as nocardial brain abscesses (nocardia asteroides) 4 weeks after the first operation. In spite of delay in the diagnosis, he was relieved by operations (three times) and chemotherapy including high doses of Sulfamethoxazole-Trimethoprim. He was eventually discharged. We stress the necessity of early diagnosis and the efficacy of Sulfamethoxazole-Trimethoprim for nocardial brain abscess.

Determination of sulfadimethoxine, sulfamethoxazole, trimethoprim and their main metabolites in porcine plasma by column switching HPLC

A HPLC method for the determination of sulfadimethoxine, sulfamethoxazole, trimethoprim and their main metabolites in porcine plasma is reported. The metabolites under investigation were the N4-acetyl sulfonamides and 3'- and 4'-demethyl trimethoprim. In order to obtain a sensitivity of 25-50 ng ml-1, the application of column switching HPLC was investigated. An on-line preconcentration of the drugs and metabolites was preceded by an off-line sample pre-treatment. Parent compounds and metabolites were separated by reversed-phase HPLC followed by UV-detection. The mean recoveries for 4'-demethyl trimethoprim were greater than 80% while the mean recoveries for the other compounds were greater than 90%. Application of the method for analysis of plasma samples obtained from pharmacokinetic studies is described.

High-performance liquid chromatographic analysis of trimethoprim and sulfamethoxazole in microliter volumes of chinchilla middle ear effusion and serum

A reversed-phase high-performance liquid chromatographic procedure was developed to analyze 25-microliters volumes of chinchilla middle ear effusion and 50-microliters volumes of serum for trimethoprim and sulfamethoxazole. The small sample volumes were dictated by the chinchilla model of otitis media and our need to collect multiple samples over a 12-h drug dosing interval. The drugs were separated on a cyanopropylsilane column using acetonitrile-40 mM sodium phosphate, (16:84, v/v), pH 4.8. Trimethoprim and the internal standard were detected at 230 nm while sulfamethoxazole was detected at 250 nm. Middle ear effusion and serum samples were extracted with ethyl acetate-dichloromethane (25:75, v/v). The limit of quantitation was 0.5 micrograms/ml for sulfamethoxazole and 0.1 micrograms/ml for trimethoprim (coefficient of variation less than 20%), the limit of detection 0.25 and 0.05 micrograms/ml, respectively. Middle ear and serum samples of chinchilla with experimentally induced otitis media receiving 10 mg/kg trimethoprim and 50 mg/kg sulfamethoxazole intramuscularly were collected over a 12-h period and analyzed. All statistics that validate the analytic method are reported.

[Studies of the pharmacokinetics and bioavailability of a new trimethoprim/sulfamethoxazole preparation in healthy volunteers]

The objective of this study was to determine both the pharmacokinetic parameters and the bioavailability of a newly developed trimethoprim/sulfamethoxazole preparation (cotrimoxazole, Kepinol forte, 160 mg of trimethoprim/800 mg of sulfamethoxazole) in comparison with a reference preparation customary in trade and registered according to the AMG 1976, after single oral administration. For this purpose the test and the reference preparation were examined in a randomized 2-way crossover design (Latin square) in 12 volunteers each. Both dosage forms led to maximum plasma levels of approx. 1250 ng/ml of trimethoprim and about 40 micrograms/ml of sulfamethoxazole 1.5-2 h after application; the plasma half-lives were about 9 h for trimethoprim and around 8.5 h for sulfamethoxazole. The statistical comparison (ANOVA, confidence intervals according to Westlake, Pratt-Wilcoxon test) of the pharmacokinetic parameters found in the study resulted in bioequivalence of the newly developed trimethoprim/sulfamethoxazole preparation and the reference preparation. Furthermore, after the administration of both preparations no marked side effects worth mentioning were observed, suggesting a good and comparable clinical tolerability of the two preparations.