Chemometric and derivative methods as flexible spectrophotometric approaches for dissolution and assaying tests in multicomponent tablets

Two derivative spectrophotometric (ratio derivative spectra and algorithm bivariate calibration) and a chemometric methods (partial least squares, PLS) are proposed for the simultaneous determination of binary mixtures in tablet analysis and dissolutions tests, without prior separation. These approaches are successfully applied to quantify trimethoprim (TMP) combined with sulfamethoxazole (SMX) or sulfamethazine (SMZ) or sulfafurazole (SFZ) using the information in the absorption spectra of appropriate solutions. Beer's law was obeyed in the concentration range of 0.98-17.5 microg/ml for TMP, 0.95-17.2 microg/ml for SMX, 1.16-17.5 microg/ml for SMZ and 0.97-17.4 microg/ml for SFZ. The first derivative (1D) bivariate algorithm method involves the use of four calibration curves: two for each compound at two different wavelengths, selected by Kaiser's method. Similarly, the first derivative ratio spectrophotometry employs the linear relationship between the ratio spectra of the analytes and the concentration range. The results were compared with those obtained by PLS multivariate calibration. The calibration models from PLS were pre-treated by orthogonal signal correction and evaluated by cross-validation using the 'SIMCA-P 9' software. Synthetic mixtures of TMP and sulfonamides were used in five different sets for the validity of the calibrations. Mean recoveries for derivative ratio, derivative bivariate and PLS methods were found to be between 99.7% and 102.0% for TMP, 99.4% and 100.2% for SMX, 99.3% and 101.0% for SMZ and 98.1% and 102.3% for SFZ. The calibrations of the three methods were successfully applied to the assaying and dissolution of placebo and commercial tablets without any prior separation. More than 85% of TMP, SMX and SMZ were dissolved within 15 min. For SFZ, only 85% of the compound was dissolved after 60 min. In this study, the three spectrophotometric methods can be satisfactorily used for the quantitative analysis and for dissolution tests of multicomponent dosage forms.     

Correlation between chromatographic fingerprint and antioxidant activity of Turnera diffusa (Damiana)

In the present contribution, the partial least squares (PLS) method was used to establish a correlation between the antioxidant activity (obtained by DPPH assay) and chromatographic profiles of TURNERA DIFFUSA extracts. Chromatograms were obtained using HPLC-DAD. A model was constructed using 40 samples with 2550 X variables corresponding to the responses obtained at different times; the Y variables consisted of experimental values of antioxidant activity of each extract (measured as EC??). Prior to this analysis, alignment of chromatograms was performed based on consideration of seven high-intensity signals present in all samples. The PLS1 model was validated by cross-validations; its capacity was evaluated using correlation parameters R2, root mean square error of calibration (RMSEC), and root mean square error of prediction (RMSEP). The best results were achieved with zero order chromatograms using five-point smoothing (R2?=?0.96, RMSEC?=?3.31, and RMSEP?=?7.86). Under these conditions, the optimal number of components was five. The model was applied to the prediction of antioxidant activity of commercial products; no significant differences were found between the experimental and predicted antioxidant activities for 83?% of them.     

High-performance liquid chromatographic assay for the simultaneous measurement of trimethoprim and sulfamethoxazole in plasma or urine

Procedures for the simultaneous determination of trimethoprim (TMP) and sulfamethoxazole (SMX) in plasma or urine are reported. The drugs are extracted from plasma or urine by a single solid-phase extraction and quantitated by high-performance liquid chromatography. Both drugs are analyzed in the same chromatographic run. Intra- and interassay variability are less than 10% for both compounds, and the recovery and precision of TMP measurement are unaffected by concurrent SMX concentrations. Limits of quantitation for TMP and SMX in plasma were 0.02 and 0.21 microgram/ml, respectively. In urine, the limit of quantitation for both drugs was 1.0 microgram/ml. Metabolites of TMP and SMX did not interfere with the assay. Pharmacokinetic parameters from volunteers given two formulations of co-trimoxazole in a crossover comparison study are reported.     

Simultaneous determination of sulphamethoxazole and trimethoprim in powder mixtures by attenuated total reflection-Fourier transform infrared and multivariate calibration

A partial least-squares calibration (PLS) procedure in combination with infrared spectroscopy has been developed for simultaneous determination of sulphamethoxazole (SMZ) and trimethoprim (TMP) in raw material powder mixtures used for manufacturing commercial pharmaceutical products. Multivariate calibration modeling procedures, interval partial least squares (iPLS) and synergy partial least squares (siPLS), were applied to select a spectral range that provided the lowest prediction error in comparison to the full-spectrum model. The experimental matrix was constructed using 49 synthetic samples and 15 commercial samples. The considered concentration ranges were 400–900 mg g⁻¹ SMZ and 80–240 mg g⁻¹ TMP. Spectral data were recorded between 650 and 4000 cm⁻¹ with a 4 cm⁻¹ resolution by Fourier transform infrared spectroscopy coupled with attenuated total reflectance (ATR-FTIR) accessory. The proposed procedure was compared with conventional procedure by high performance liquid chromatography (HPLC) using 15 commercial samples containing SMZ and TMP. The results showed that PLS regression model combined to ATR-FTIR is a relatively simple, rapid and accurate procedure that could be applied to the simultaneous determination of SMZ and TMP in routine quality control of powder mixtures. A root mean square error of prediction (RMSEP) of 13.18 mg g⁻¹ for SMZ and 6.03 mg g⁻¹ for TMP was obtained after selection of better intervals by siPLS. Using the proposed procedure it is possible to analyze each sample in less than 3 min considering two replicates (excluding the grinding step). Accuracy was checked by comparison to HPLC method and agreement better than 98.8% was achieved.     

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.     

Multivariate analysis of paracetamol, propiphenazone, caffeine and thiamine in quaternary mixtures by PCR, PLS and ANN calibrations applied on wavelet transform data

The quantitative resolution of a quaternary pharmaceutical mixture consisting of paracetamol, propiphenazone, caffeine and thiamine was performed by the simultaneous use of fractional wavelet transform (FWT) with principal component regression (PCR), partial least squares (PLS) and artificial neural networks (ANN) methods. A calibration set consisting of 22 mixture solutions was prepared by means of an orthogonal experimental design and their absorption spectra were recorded in the spectral range of 210.0–312.3 nm and then transferred into the fractional wavelet domain and processed by FWT. The chemometric calibrations FWT–PCR, FWT–PLS and FWT–ANN were computed by using the relationship between the coefficients provided by FWT method and the concentration data from calibration set. An external validation was carried out by applying the developed methods to the analysis of synthetic mixtures of the related compounds, obtaining successful results. The models were finally used to assay the studied drugs in the commercial pharmaceutical formulations.     

Evaluation of chemometric algorithms in quantitative X-ray powder diffraction (XRPD) of intact multi-component consolidated samples

Quantitative X-ray powder diffraction (XRPD) data obtained from intact, consolidated samples affords the opportunity to analyze mixtures that simulate pharmaceutical drug products without the need for reversion back to powders; an analytical preparation step that destroys the contextual solid-state information intrinsic to intact consolidated samples. Traditional, standardless quantitative methods generally involve sophisticated pattern refinement procedures (e.g., Rietveld refinement) and are limited to crystalline materials. Methods that incorporate an internal standard are not optimal for compact analysis, and may often be susceptible to prediction errors associated with intensity attenuation. Chemometric-based XRPD utilizes full-pattern methods that combine analyses of both Bragg diffraction and diffuse scatter, thereby allowing for enhancement of signal-to-noise, sensitivity, and selectivity. Classical least-squares (CLS) regression, principal components regression (PCR) and partial least squares (PLS) regression are three chemometric algorithms commonly employed in spectroscopy. In the present work, quantification of a consolidated four-component system, composed of two crystalline materials and two disordered materials was analyzed intact, using two different XRPD optics geometries. Calibrations constructed for the prediction of individual constituent concentrations using the aforementioned three multi-variate algorithms were statistically compared with traditional diffraction–absorption univariate calibration. PLS regression modeling of data collected in transmission geometry provided the best statistical results for the quantification of constituent concentration. Further, this calibration was minimally affected by diffraction pattern anomalies traditionally corrected prior to phase quantification.     

重症患者复方磺胺甲(口恶)唑血药峰浓度与不良反应的相关性研究

目的:评估重症患者使用复方磺胺甲■唑发生的不良反应与血药峰浓度(C_max)的相关性及其毒性阈值。方法:采用回顾性研究的方法,收集2016年1月至2021年12月某三甲医院重症监护室使用复方磺胺甲■唑治疗并进行治疗药物监测的患者信息,使用Naranjo评分量表评价复方磺胺甲■唑与不良反应的关联性,并分析磺胺甲■唑及甲氧苄啶C_max与不良反应发生之间的相关性。结果:本研究共获得109人次磺胺甲■唑的浓度数据及87人次甲氧苄啶的浓度数据,未发现皮疹、恶心呕吐、肝毒性及肾毒性的发生与磺胺甲■唑及甲氧苄啶C_max有相关性(P>0.05),发生血液系统毒性及高钾血症的患者其甲氧苄啶C_max显著高于未发生的患者(P<0.05),进一步通过受试者工作特征曲线分析得到高钾血症的甲氧苄啶C_max最佳阈值为8.75μg·mL^-1。结论:有必要对使用复方磺胺甲■唑的重症患者进行治疗药物监测,甲氧苄啶C_max>8.75μg·mL^-1...     

A reversed-phase high-performance liquid chromatography method for the determination of cotrimoxazole (trimethoprim/ sulphamethoxazole) in children treated for malaria

A high-performance liquid chromatography (HPLC) method was developed for the simultaneous analysis of trimethoprim (TMP), sulphamethoxazole (SMX), and acetylsulphamethoxazole (AcSMX) in small amounts of blood. The method involved precipitation with 50 microL trichloracetic acid (1M) to 125 microL plasma or serum sample. 60 microL supernatant was added to 60 microL mobile phase, modified with 50microL 1 M sodium hydroxide/mL. The mobile phase consisted of 20% acetonitrile and 80% phosphate buffer adjusted to pH 6.15. Using 125 microL of the sample, limits of quantitation were 0.1 microg/mL for TMP, 1.0 microg/mL for SMX, and 1.0 microg/mL for AcSMX. The precision of the method was 2% to 11% over the range of concentrations tested, 0.5-30 microg/mL for TMP, 5-300 microg/mL for SMX, and 2.5-150 microg/mL for AcSMX, respectively. No interference with other commonly used drugs was observed. The method is rapid, simple, specific, and sensitive enough for pharmacokinetic studies. The small amount of blood required makes it suitable for pediatric patients. The method was used to analyze samples from Tanzanian children aged 6-59 months participating in a cotrimoxazole (TMP/SMX)/chloroquine randomized trial for the treatment of uncomplicated malaria. Venous blood samples from 68 children were collected 2 hours after the first dose of TMP/SMX (4 mg/kg TMP/20 mg/kg SMX at two divided doses for 5 days) and again at treatment day 4. Individual variations in plasma concentrations of TMP, SMX, and AcSMX were considerable. The mean and SEM plasma concentrations (g/mL) of TMP, SMX, and AcSMX 2 hours after the first treatment dose were 2.0 +/- 1.0 (range 0.5-6), 53 +/- 22 (range 24-146), and 13.5 +/- 12 (range 0-65), respectively. On the fourth day the attained plasma concentrations were not significantly different from samples collected after the first dose.     

Simultaneous estimation of ramipril, acetylsalicylic acid and atorvastatin calcium by chemometrics assisted UV-spectrophotometric method in capsules

In the present work, three different spectrophotometric methods for simultaneous estimation of ramipril, aspirin and atorvastatin calcium in raw materials and in formulations are described. Overlapped data was quantitatively resolved by using chemometric methods, viz. inverse least squares (ILS), principal component regression (PCR) and partial least squares (PLS). Calibrations were constructed using the absorption data matrix corresponding to the concentration data matrix. The linearity range was found to be 1-5, 10-50 and 2-10 μg mL-1 for ramipril, aspirin and atorvastatin calcium, respectively. The absorbance matrix was obtained by measuring the zero-order absorbance in the wavelength range between 210 and 320 nm. A training set design of the concentration data corresponding to the ramipril, aspirin and atorvastatin calcium mixtures was organized statistically to maximize the information content from the spectra and to minimize the error of multivariate calibrations. By applying the respective algorithms for PLS 1, PCR and ILS to the measured spectra of the calibration set, a suitable model was obtained. This model was selected on the basis of RMSECV and RMSEP values. The same was applied to the prediction set and capsule formulation. Mean recoveries of the commercial formulation set together with the figures of merit (calibration sensitivity, selectivity, limit of detection, limit of quantification and analytical sensitivity) were estimated. Validity of the proposed approaches was successfully assessed for analyses of drugs in the various prepared physical mixtures and formulations.     

Evaluation of in vitro sensitivity testing methods of detecting sulphamethoxazole trimethoprim synergy. Correlation with mouse protection assay

To evaluate the applicability of sensitivity tests in the detection of synergy between sulphamethoxazole (SMX) and trimethoprim (TMP) hospital strains of Escherichia coli were tsted by the disc sensitivity and the agar dilution tests using Isosensitest agar; sensitivity to SMX, TMP and 20 parts sulphamethoxazole plus 1 part trimethoprim (SXT) was determined. Ten of 19 strains of E. coli showed larger zones of inhibition with the SXT discs than with either SMX or TMP discs. Yet all 19 E. coli strains showed appreciably lower MIC for SXT than either SMX or TMP in the agar dilution test. It is concluded that disc sensitivity tests do not detect synergy between SMX and TMP. Demonstration of a lower MIC with SXT than either SMX or TMP in the agar dilution test is a better indication of synergy. This conclusion is confirmed in the mouse protection tests.     

近红外光谱—偏最小二乘方法同时测定复方磺胺甲唑片的两种有效成分

目的建立复方磺胺甲口恶唑片的两种有效成分磺胺甲口恶唑(SMZ)和甲氧苄啶(TMP)的快速同时测定方法。方法基于近红外漫反射光谱技术,利用偏最小二乘方法建立该复方中SMZ和TMP的定量分析多元校正模型。结果对于所建立的SMZ与TMP模型,相关系数分别为:100.00%与100.00%;校正集残差分别为:0.0163与0.008 36;预测均方差分别为:0.156与0.0815。结论本方法在样品不经任何预处理的情况下,实现了该制剂的两种有效成分SMZ和TMP的简单、快速、两组分同时准确测定。     

Comparative study of the continuous wavelet transform, derivative and partial least squares methods applied to the overlapping spectra for the simultaneous quantitative resolution of ascorbic acid and acetylsalicylic acid in effervescent tablets

The simultaneous spectrophotometric determination of ascorbic acid (AA) and acetylsalicylic acid (ASA) in effervescent tablets in the presence of the overlapping spectra was accomplished by the continuous wavelet transform (CWT), derivative spectrophotometry (DS) and partial least squares (PLS) approaches without using any chemical pre-treatment. CWT and DS calibration equations for AA and ASA were obtained by measuring the CWT and DS amplitudes corresponding to zero-crossing points of spectra obtained by plotting continuous wavelet coefficients and first-derivative absorbance values versus the wavelengths, respectively. The PLS calibration was constructed by using the concentration set and its full absorbance data consisting of 850 points from 220 to 305 nm in the range of 210-310 nm. These three methods were tested by analyzing the synthetic mixtures of the above drugs and they were applied to the real samples containing two commercial pharmaceutical preparations of subjected drugs. A comparative study was carried out by using the experimental results obtained from three analytical methodologies and precise and accurate results were obtained.     

Analyzing of the volatile chemical constituents in Artemisia capillaris herba by GC-MS and correlative chemometric resolution methods

The volatile chemical constituents in traditional Chinese medicine (TCM), Artemisia capillaris herba, were determined by gas chromatography-mass spectrometry (GC-MS). The acquired two-dimensional data were resolved by correlative chemometric resolution methods. The noise in the raw data is pretreated by roughness penalty smoothing method. With the data denoised, heteroscedastic noise and signal-to-noise ratio were decreased apparently, which was favorable to the determination of component number. The selective range can be extracted from rankmap obtained by fixed size moving window evolving factor analysis (FSMWEFA) conveniently. The overlapped chromatographic peaks were resolved into pure chromatograms and pure spectra with evolving window orthogonal projection (EWOP). The purity of the resolved pure spectra were improved furthermore with the heteroscedastic noise decreased through roughness penalty smoothing method, although the basic structure of the raw data changes little. Qualitative analysis was performed by similarity search in NIST147 and Willey library. Pure chromatograms are in favor of quantitative analysis, which was obtained by total volume integration. Forty-two of seventy-five separated constituents in essential oil, accounting for 89.03% of the total content, were identified. The result proves the combined approaches to be powerful for the analysis of complex herbal samples.     

Dissolution and assaying of multicomponent tablets by chemometric methods using computer-aided spectrophotometer

Dissolution of three component tablets containing paracetamol (APAP), propyphenazone (PP), and caffeine (CAF) was carried out by USP paddle method. Three chemometric methods; inverse least square (ILS), principal component regression (PCR) and partial least squares (PLS) were applied to simultaneous assay of APAP, PP and CAF in tablets. The PCR, PLS and ILS methods were applied to simultaneous dissolution APAP, PP and CAF in tablets using a double beam UV-Vis spectrophotometer without any chemical separation and any graphical treatment of the overlapping spectra of three drugs. Twenty two mixture solutions in different concentrations were prepared in simulated gastric juice (SGJ, USP) for the chemometric calibrations as training set. The absorbance data matrix was obtained by measuring the absorbance at 14 wavelength points (from 222.5 to 292.5 nm) with the intervals of 5 nm (Deltalambda=5 nm) in the spectral region between 200 and 310 nm. Training set and absorbance data were used for the calibrations of chemometric methods. The developed calibrations were tested for the previously prepared solutions of mixture of three drugs for the validation of the assay method. The chemometric calculations were performed by using the 'MAPLE VRSQUO; software. The results of three chemometric methods were statistically compared with each other. These chemometric calibrations were successfully applied to the content uniformity and dissolution of the multicomponent tablets without any separation procedure. The synthetic mixtures of three drugs were used for the validity of the calibrations. Means recoveries (percent) and relative standard deviation of PLS, PCR and ILS methods were found to be 100.1+/-0.6, 101.4+/-1.6 and 100.1+/-0.6 for APAP; 100.9+/-3.2, 102.0+/-3.3 and 100.9+/-3.2 for PP; 99.9+/-3.5, 101.6+/-3.3 and 99.9+/-3.2 for CAF, respectively. Dissolution profiles of three component tablets were performed. More than 95% of drugs were dissolved within 15 min. All of the three-chemometric methods in this study can be satisfactorily used for the quantitative analysis and for dissolutions test of multicomponent dosage form.     

Dissolution kinetics of three-component compressed solid mixtures with largely different solubilities: flaking spheres

The dissolution kinetics of three-component compressed solid spheres of various compositions of mannitol (MAN), sulfamethoxazole (SMX), and trimethoprim (TMP) were studied. Because the solubility of MAN was approximately 300 times that of SMX and TMP, the flaking phenomenon during dissolution process was observed. The critical flaking line was drawn between two critical flaking points in the triangular composition diagram of MAN-SMX-TMP mixtures (i.e., the compositions of 0.5022 MAN and 0.4978 SMX mass fractions, and 0.4906 MAN and 0.5094 TMP mass fractions), thus dividing the system into two distinct regions; namely, nonflaking and flaking regions. In the case of nonflaking region, only three dissolution behaviors for MAN-SMX-TMP three-component mixtures were proposed. The calculated dissolution rates of all components by using the multicomponent dissolution model previously proposed were found to satisfactorily approximate the observed values for both two- and three-component solid mixtures. In the case of flaking region, the observed dissolution rate of MAN was found to be the exponential function of the mass fraction ratio of either SMX or TMP to MAN for both two- and three-component mixtures. The slope of the semilogarithmic plot of the observed MAN dissolution rate versus the mass fraction ratio of either SMX or TMP to MAN was defined as retarding coefficients of SMX or TMP, r'(SMX) or r'(TMP), respectively. The erosion rate of either SMX or TMP was the product of mass fraction ratio of drug to MAN and the exponential function of such mass fraction ratio. The mathematical model was developed on the basis of simultaneous erosion followed by dissolution of eroded particles to predict the dissolution rate of each drug from MAN-SMX-TMP compressed solid spheres within the flaking region.     

Trimethoprim/sulfametrole: evaluation of the available clinical and pharmacokinetic/pharmacodynamic evidence

Emergence of resistance to widely used trimethoprim/sulfamethoxazole (TMP/SMX) as well as common adverse events in human immunodeficiency virus (HIV)-infected patients casts interest on combinations of TMP with other sulfonamides. Sulfametrole (SMT) combined with TMP could provide a choice for difficult-to-treat infections, particularly when administered intravenously. The objective of this review was to evaluate the available clinical and pharmacokinetic/pharmacodynamic (PK/PD) evidence regarding TMP/SMT, particularly in comparison with TMP/SMX. We reviewed the available evidence retrieved from searches in PubMed/Scopus/Google Scholar and by bibliography hand-searching. In total, 46 eligible studies (most published before 1997) were identified, 7 regarding intravenous (i.v.) TMP/SMT, 24 regarding oral TMP/SMT and 15 providing comparative data for TMP/SMT versus TMP/SMX. The antimicrobial activity of TMP/SMT was similar to TMP/SMX for Gram-positive isolates. A greater percentage of Escherichia coli and Proteus spp. isolates were susceptible to TMP/SMT compared with TMP/SMX. PK/PD data suggest a dosage adjustment of i.v. TMP/SMT in patients with seriously impaired renal function. Four randomised controlled trials and 16 non-comparative studies reported good effectiveness/safety outcomes for oral TMP/SMT in genital ulcers (mainly chancroid), respiratory tract infections and urinary tract infections (UTIs). Moreover, i.v. TMP/SMT was effective against Pneumocystis jiroveci infection in HIV-infected patients, severe pneumonia and UTIs. In one study, hypersensitivity reactions occurred in 18/52 (34.6%) of HIV-infected patients; 2/52 (3.8%) developed psychosis. Gastrointestinal adverse events were mild and rare. Excipients in i.v. TMP/SMT formulations might be less toxic compared with i.v. TMP/SMX formulations, particularly for children. In conclusion, despite the scarcity of contemporary evidence, available data suggest that TMP/SMT could be an alternative treatment option to TMP/SMX, even in serious infections, when administered intravenously.     

The association of opportunistic infections with the occurrence of trimethoprim/sulfamethoxazole hypersensitivity in patients infected with human immunodeficiency virus

Hypersensitivity from trimethoprim/sulfamethoxazole (TMP/SMX) has been linked to a reactive nitroso intermediate from sulfamethoxazole metabolism, which may be altered in patients with human immunodeficiency virus (HIV) infection. The authors determined the clinical factors that are associated with TMP/SMX hypersensitivity in patients with HIV. In a case control study, 54 controls currently tolerating TMP/SMX prophylaxis were randomly matched by date of hypersensitivity reaction in case patients to 28 patients with a history of a rash consistent with erythema multiforme from TMP/SMX. Demographic data, coadministered medications, laboratory data, and histories of opportunistic infections were extracted on all patients. A highly significant association was observed between the number of opportunistic infections and the occurrence of TMP/SMX hypersensitivity (p < 0.001), despite comparability of CD4 counts between case patients and controls (p > 0.1). A tendency for protection from TMP/SMX hypersensitivity in blacks was also observed (p = 0.066). These observations suggest that the mechanisms by which HIV produces cellular immune dysfunction and alters drug detoxification may be linked.     

Simultaneous determination of binary mixtures of trimethoprim and sulfamethoxazole or sulphamethoxypyridazine by the bivariate calibration spectrophotometric method

The bivariate calibration algorithm was applied to the spectrophotometric simultaneous determination of trimethoprim (TMP), sulfamethoxazole (SMX) or sulphamethoxypyridazine (SMP) binary mixtures in pharmaceutical and veterinary products. The results obtained were compared with those from derivative spectrophotometry. The statistical evaluation of the method bias showed that the proposed procedure is comparable with commonly used first-derivative spectrophotometry. However, the advantage of bivariate calibration is its simplicity, due to the minimal spectra manipulation when compared with derivative techniques.