Spectrophotometric determination of pefloxacin in pharmaceutical preparations

It has been established that the antibiotic pefloxacin (Abaktal) methane-sulphonate reacts with Fe(III) at pH 1.00–8.00 to form a water-soluble complex with maximum absorbance at 360 nm. The composition of the complex, determined spectrophotometrically by the application of Job's, molar-ratio and Bent—French's methods, was pefloxacin: Fe(III) = 1:1 (pH = 2.50; λ = 360 nm; μ = 0.1 M). The relative stability constant, obtained by the methods of Sommer and Asmus was 10^5.02 (pH = 2.50; λ = 360 nm; μ = 0.1 M). The molar absorptivity of the complex at 360 nm was found to be 4.8 × 10³ l mol⁻¹ cm⁻¹, Beer's law was followed for pefloxacin concentrations of 2.15–85.88 μg ml⁻¹. The lower sensitivity limit of the method was 2.15 μg ml⁻¹. The relative standard deviation (n = 10) was 0.57–1.07%. The method can be applied to the rapid and simple determination of pefloxacin in aqueous solutions and tablets.     

Determination of meloxicam in bulk and pharmaceutical formulations

Three sensitive and reproducible methods for quantitative determination of meloxicam (mel) in pure form and in pharmaceutical formulations are presented. The first method is high performance liquid chromatography by which the drug is determined in the presence of its degradation products over concentration range 100–500 μg ml⁻¹ with mean percentage accuracy 100.13±0.53. The second method is based on measuring the absorbance of the formed neutral complex between basic methylene blue and mel in phosphate buffer (pH 8) at λ=653.5 nm over concentration range 1–5 μg ml⁻¹ with mean percentage accuracy 99.12±1.18. The third method is based on reaction between 2,3-dichloro-5,6-dicyano-p-benzoquinone resulting in the formation of an intense orange red coloured product after heating in a boiling water bath for 5 min. The coloured product exhibits an absorption maximum at 455 nm, over concentration range 40–160 μg ml⁻¹ with mean percentage accuracy 100.53±1.04.     

Use of palladium(II) chloride as colour-forming reagent in determination of pralidoxime chloride in water and tablets

Pralidoxime chloride (PAM-2Cl) has been determined spectrophotometrically in Britton—Robinson buffer solution at pH = 6.45; the method is based on measurement of the absorbance of the Pd(II)-pralidoxime complex at 327 nm. Studies of the composition of the complex by Job's continuous variation method, the molar ratio method and Bent—French's method yielded a Pd(II):pralidoxime ratio of 1:1. The conditional stability constant (K′) of the complex at the optimum pH of 6.45 and an ionic strength (μ) of 0.3 M was found to be 10^5.2. The molar absorptivity was 1.05 × 10⁴ 1 mol⁻¹ cm⁻¹. Beer's law was obeyed at concentrations up to 60 μM. The detection limit was 0.55 μg ml⁻¹. The relative standard deviation (N = 10) was 0.28–1.03%. The method was accurate and sensitive for the analysis of PAM-2Cl in water and tablets.     

Spectrophotometric study of polythiazide—palladium(II) complex

A quantitative spectrophotometric method using Pd(II) chloride as analytical reagent for the determination of polythiazide in pharmaceutical preparations is described in this study. It has been found that polythiazide reacts with Pd(II) chloride in the pH range 3.6–5.8, forming a red, water-soluble (1:1) complex with maximum absorbance at 527 nm. At the optimum pH of 4.8 and an ionic strength μ = 0.1 M, the conditional stability constant of the complex is found to be log K′ = 4.77. The molar absorptivity at 527 nm is 3.2 × 10³ 1 mol⁻¹ cm⁻¹. Good agreement with Beer's law was found for polythiazide concentrations up to 2.2 mmol l⁻¹. The nominal percent recovery of polythiazide was 99.5% (n = 20). The simplicity, selectivity and sensitivity of the method described is suitable for rapid and accurate determinations of polythiazide in tablets.     

Simultaneous separation and determination of active components in Cordyceps sinensis and Cordyceps militarris by LC/ESI-MS

A simple and rapid isocratic LC/MS coupled with electrospray ionization (ESI) method for simultaneous separation and determination of adenine, hypoxanthine, adenosine and cordycepin in Cordyceps sinensis (Cs) and its substitutes was developed. 2-Chloroadenosine was used as internal standard for this assay. The optimum separation for these analytes was achieved using the mixture of water, methanol and formic acid (85:14:1, v/v/v) as a mobile phase and a 2.0×150 mm Shimadzu VP-ODS column. Selective ion monitoring (SIM) mode ([M+H]⁺ at m/z 136, 137, 268, 252 and 302) was used for quantitative analysis of above four active components. The regression equations were liner in the range of 1.4–140.0 μg ml⁻¹ for adenine, 0.6–117.5 μg ml⁻¹ for hypoxanthine, 0.5–128.5 μg ml⁻¹ for adenosine and 0.5–131.5 μg ml⁻¹ for cordycepin. The limits of quantitation (LOQ) and detection (LOD) were, respectively 1.4 and 0.5 μg ml⁻¹ for adenine, 0.6 and 0.2 μg ml⁻¹ for hypoxanthine, 0.5 and 0.1 μg ml⁻¹ for adenosine and cordycepin. The recoveries of four constituents were from 93.5 to 107.0%. The nucleoside contents of various types of natural Cs and its substitutes were determined and compared with this developed method.     

A rapid colorimetric method for the determination of Losartan potassium in bulk and in synthetic mixture for solid dosage form

Two new rapid reproducible and economical spectrophotometric methods are described for the determination of Losartan potassium in bulk and in synthetic mixture for solid dosage forms. Both methods are based on the formation of an orange-red and orange ion-pair complex due to the action of Calmagite (CT) and Orange-II (O-II) on Losartan potassium in acidic medium (pH 1.2). Under optimised conditions, they show an absorption maxima at 491 nm (CT) and 486 nm (O-II), with molar absorptivities of 1.74×10³ and 1.75×10³ l mol⁻¹ cm⁻¹ and Sandell's sensitivities of 0.2649 and 0.2637 per 0.001 absorbance unit for CT and O-II, respectively. The colour is stable for 5 min after extraction. In both cases Beer's law is obeyed between 10 and 100 μg ml⁻¹. The proposed method was successfully extended to synthetic mixture for solid dosage forms.     

Spectrophotometric and atomic absorption spectrometric determination of certain cephalosporins

Two sensitive spectrophotometric and atomic absorption spectrometric procedures are developed for the determination of certain cephalosporins (cefotaxime sodium and cefuroxime sodium). The spectrophotometric methods are based on the charge-transfer complex formation between these drugs as n-donors and 7,7,8,8-tetracyano-quinodimethane (TCNQ) or p-chloranilic acid (p-CA) as π-acceptors to give highly coloured complex species. The coloured products are measured spectrophotometrically at 838 and 529 nm for TCNQ and p-CA, respectively. Beer’s law is obeyed in a concentration range of 7.6–15.2 and 7.1–20.0 μg ml⁻¹ with TCNQ, 95.0-427.5 and 89.0-400.5 μg ml⁻¹ with p-CA for cefotaxime sodium and cefuroxime sodium, respectively. The atomic absorption spectrometric methods are based on the reaction of the above cited drugs after their alkali-hydrolysis with silver nitrate or lead acetate in neutral aqueous medium. The formed precipitates are quantitatively determined directly or indirectly through the silver or lead content of the precipitate formed or the residual unreacted metal in the filtrate by atomic absorption spectroscopy. The optimum conditions for hydrolysis and precipitation have been carefully studied. Beer’s law is obeyed in a concentration range of 1.9–11.4 and 1.78–8.90 μg ml⁻¹ with Ag(I), 14.2–57.0 and 13.3–53.4 μg ml⁻¹ with Pb(II) for cefotaxime sodium and cefuroxime sodium, respectively (for both direct and indirect procedures). The spectrophotometric and the atomic absorption spectrometric procedures hold well their accuracy and precision when applied to the analysis of cefotaxime sodium and cefuroxime sodium dosage forms.     

Simultaneous LC determination of paracetamol and related compounds in pharmaceutical formulations using a carbon-based column

A simple, rapid and convenient high performance liquid chromatographic method, which permits the simultaneous determination of paracetamol, 4-aminophenol and 4-chloracetanilide in pharmaceutical preparation has been developed. The chromatographic separation was achieved on porous graphitized carbon (PGC) column using an isocratic mixture of 80/20 (v/v) acetonitrile/0.05 M potassium phosphate buffer (pH 5.5) and ultraviolet detection at 244 nm. Correlation coefficient for calibration curves in the ranges 1–50 μg ml⁻¹ for paracetamol and 5–40 μg ml⁻¹ for 4-aminophenol and 4-chloroacetanilide were >0.99. The sensitivity of detection is 0.1 μg ml⁻¹ for paracetamol and 0.5 μg ml⁻¹ for 4-aminophenol and 4-chloroacetanilide. The proposed liquid chromatographic method was successfully applied to the analysis of commercially available paracetamol dosage forms with recoveries of 98–103%. It is suggested that the proposed method should be used for routine quality control and dosage form assay of paracetamol in pharmaceutical preparations. The chromatographic behaviour of the three compounds was examined under variable mobile phase compositions and pH, the results revealed that selectivity was dependent on the organic solvent and pH used. The retention selectivity of these compounds on PGC was compared with those of octadecylsilica (ODS) packing materials in reversed phase liquid chromatography. The ODS column gave little separation for the degradation product (4-aminophenol) from paracetamol, whereas PGC column provides better separation in much shorter time.     

A capillary GC-MS method for analysis of phenytoin and [C3]-phenytoin from plasma obtained from pulse dose pharmacokinetic studies

Stable isotope analogues of phenytoin are useful for pulse dose pharmacokinetic studies in epilepsy patients. A simultaneous assay was developed to quantitate phenytoin (5,5-diphenylhydantoin) and its stable isotope analogue [¹³C₃]-phenytoin (5,5-diphenyl-2,4,5-¹³C₃-hydantoin) from plasma. Quantitation was achieved by GC-MS analysis of liquid/liquid extracted plasma samples, with [²H₁₀]-phenytoin (5,5-di(pentadeuterophenyl)-hydantoin) as an internal standard. The total coefficients of variance (C.V._t) were <7% for phenytoin (2.5–40 μg ml⁻¹) and <10.3% for [¹³C₃]-phenytoin (0.1–6.0 μg ml⁻¹). The accuracy of the assay varied from 87.8–100.1% (phenytoin, 2.5–40 μg ml⁻¹) and 89.6–116.3% ([¹³C₃]-phenytoin, 0.02–6.0 μg ml⁻¹). The assay was tested under in vivo conditions by administration of a pulse dose of the stable isotope analogue to a single rat dosed to steady-state with fosphenytoin, a phenytoin prodrug. The results of the in vivo experiment demonstrate the usefulness of this assay for future pharmacokinetic studies in special population epilepsy patients.     

Bead injection spectroscopy-flow injection analysis (BIS-FIA): an interesting tool applicable to pharmaceutical analysis. Determination of promethazine and trifluoperazine

A bead injection spectroscopy-flow injection analysis (BIS-FIA) system for the spectrophotometric detection of promethazine and trifluoperazine is developed. The sensor is based in the oxidation of the phenothiazines by Fe(III) which is later determined by formation of the complex between Fe(II) and Ferrozine, [FeFz₃]⁴⁻. Immediately, this complex is retained on a homogeneous bead suspension of Sephadex QAE A-25 resin (500 μl) which has been injected previously in the system to fill a commercial flow-cell (Hellma 138-OS). The use of BI with respect to the use of a reusable flow-through sensor is justified because the complex is so strongly retained on the beads that the regeneration of the solid support becomes extraordinarily difficult in the proposed method. At the end of the analysis, beads are automatically discarded from the flow-cell, by reversing the flow, and transported out of the system. The analytical signals are measured at a wavelength of 567 nm, corresponding to the absorbance of the complex. Using a sample volume of 600 μl, the analytical signal showed a very good linearity in the range 0.5–8.0 μg ml⁻¹ and 0.5–10.0 μg ml⁻¹, with detection limits of 0.09 and 0.14 μg ml⁻¹ for promethazine and trifluoperazine, respectively. R.S.D.s (%) lower than 2% were obtained for both analytes. The proposed method is highly selective in the presence of other species that are normally encountered with these analytes. The sensor was satisfactorily applied to pharmaceutical preparations.     

Spectrophotometric and atomic absorption spectrometric determination of ramipril and perindopril through ternary complex formation with eosin and Cu(II)

Two sensitive, spectrophotometric and atomic absorption spectrometric procedures are developed for the determination of ramipril and perindopril. Both methods are based on the formation of a ternary complex, extractable with chloroform, between copper(II), eosin and the two cited drugs. Spectrophotometrically under the optimum condition, the ternary complexes showed an absorption maximum at 535 nm, with apparent molar absorptivities of 6.55 and 4.00×10³ mol⁻¹cm⁻¹ and Sandell’s sensitivities of 5.80×10⁻² and 1.04×10⁻¹μg cm⁻² for perindopril and ramipril, respectively. The solution of ternary complex obeyed Beer’s law in concentration ranges 10–60 and 20–100 μg ml⁻¹ for perindopril and ramipril, respectively. The proposed method was applied to the determination of the two cited drugs in pharmaceutical tablets. The atomic absorption spectrometric method, directly through the quantitative determination of copper content of the organic extract of the complex, was also investigated for the purpose of enhancing the sensitivity of the determination. The spectrophotometric and atomic absorption spectrometric procedures hold their accuracy and precision well when applied to the determination of ramipril and perindopril dosage forms.     

Oxidation of adrenaline and noradrenaline by solved molecular oxygen in a FIA assembly

A simple and effective procedure is proposed for the study and simultaneous determination of adrenaline and noradrenaline. The fluorimetric determination of both substances is performed in a flow injection assembly and by oxidation of both drugs with the solved molecular oxygen. The influence of different parameters is empirically studied and the interpretation of the reaction mechanism is also added. The determination of adrenaline is monitored at 450 nm and the outputs at 520 nm correspond to the adrenaline and noradrenaline global amount; for both lectures λ_exc 329 nm. The influence of temperature is relevant and analytical determination occurred at 55 °C by immersing the sample loop in a water bath. The linear range for adrenaline is over 0.5–20 μg ml⁻¹, limit of detection for both compounds is 0.2 μg ml⁻¹: the influence of foreign compounds as potential interferents is also tested; and, finally the procedure is applied to determination of both chatecolamines in synthetic samples.     

Simultaneous analysis of methylprednisolone, methylprednisolone succinate, and endogenous corticosterone in rat plasma

A reversed-phase HPLC method is reported for simultaneous quantitation of methylprednisolone (MP), MP succinate (MPS), and endogenous corticosterone (CST) in plasma of rats. Additionally, the 11-keto metabolite of MP (methylprednisone, MPN) is resolved from the other analytes. After addition of internal standard (triamcinolone acetonide; IS) and an initial clean up step, the analytes of interest are extracted into methylene chloride. The steroids are then resolved on a reversed-phase polymer column using a mobile phase of 0.1 M acetate buffer (pH 5.7): acetonitrile (77:23) which is pumped at a flow rate of 1.5 ml min⁻¹. Sample detection was accomplished using an UV detector at a wavelength of 250 nm. All the five components (MPS, MP, MPN, CST and IS) were baseline resolved from each other and other components of plasma. Linear relationships were found between the steroids: IS peak area ratios and plasma concentrations in the range of 0.1–4 μg ml⁻¹ for MP and MPS and 0.1–1.0 μg ml⁻¹ for MPN and CST. The assay is accurate as intra- and inter-run error values were <±8% for all the components. Further, the intra- and inter-run CVs of the assay were <16% at all the concentrations and for all the components. The application of the assay was demonstrated after the injection of a single 5 mg kg⁻¹ (MP equivalent) dose of MPS or a macromolecular prodrug of MP to rats.     

Flow injection and HPLC determination of furosemide using pulsed amperometric detection at microelectrodes

The flow-injection and HPLC determination of the diuretic drug furosemide using pulsed amperometric detection (PAD) at cylindrical carbon fibre microelectrodes (CFMEs) is reported. Experimental conditions such as pH (6.5) and buffer concentration (0.05 mol l⁻¹ HPO₄²⁻/H₂PO₄⁻) were optimized using square-wave voltammetry (SWV). Repetitive flow-injection amperometric measurements at +1.25 V for furosemide showed a continuous decrease in the peak current, probably as a consequence of the microelectrode surface fouling. However, a suitable amperometric detection of furosemide was achieved using a PAD program consisting of a two-step potential waveform with alternating anodic and cathodic polarization. The anodic (detection) potential was +1.25 V (time of application 0.1 s), and the cathodic (cleaning) potential was −0.20 V (t=0.2 s). A linear calibration graph was obtained for furosemide in the 5.0×10⁻⁷–1.0×10⁻⁴ mol l⁻¹ concentration range, with a limit of detection of 1.7×10⁻⁷ mol l⁻¹. HPLC-PAD at carbon fibre microelectrodes was used for the determination of furosemide in the presence of several thiouracil drugs and oxytetracycline (OTC). The mobile phase selected was a 25:75 acetonitrile:5.0×10⁻³ mol l⁻¹ NaH₂PO₄ (pH 5.0) mixture. A linear calibration graph was obtained for furosemide in the 1–100 μM range, with a limit of detection of 0.55 μM. The usefulness of this method for the determination of furosemide in real samples was evaluated by performing the analysis of commercial milk samples spiked with furosemide at a concentration level of 4.5×10⁻⁷ mol l⁻¹ (150 ng ml⁻¹), as well as with other thiouracil drugs and OTC. A mean recovery of 95±5% furosemide was obtained.     

Lobeline inhibits nicotine-evoked [H]dopamine overflow from rat striatal slices and nicotine-evoked Rb efflux from thalamic synaptosomes

The present study evaluated the interaction of lobeline with neuronal nicotinic acetylcholine receptors using two in vitro assays, [³H] overflow from [³H]dopamine ([³H]DA)-preloaded rat striatal slices and ⁸⁶Rb⁺ efflux from rat thalamic synaptosomes. To assess agonist interactions, the effect of lobeline was determined and compared to S(−)-nicotine. To assess antagonist interactions, the ability of lobeline to inhibit the effect of S(−)-nicotine was determined. Both S(−)-nicotine (0.1–1 μM) and lobeline (>1.0 μM) evoked [³H] overflow from superfused [³H]DA-preloaded striatal slices. However, lobeline-evoked [³H] overflow is mecamylamine-insensitive, indicating that this response is not mediated by nicotinic receptors. Moreover, at concentrations (<1.0 μM) which did not evoke [³H] overflow, lobeline inhibited S(−)-nicotine (0.1–10 μM)-evoked [³H] overflow, shifting the S(−)-nicotine concentration–response curve to the right. S(−)-Nicotine (30 nM–300 μM) increased (EC₅₀ VALUE=0.2 μM) ⁸⁶Rb⁺ efflux from thalamic synaptosomes. In contrast, lobeline (1 nM–10 μM) did not evoke ⁸⁶Rb⁺ efflux, and the lack of intrinsic activity indicates that lobeline is not an agonist at this nicotinic receptor subtype. Lobeline completely inhibited (IC₅₀ VALUE=0.7 μM) ⁸⁶Rb⁺ efflux evoked by 1 μM S(−)-nicotine, a concentration which maximally stimulated ⁸⁶Rb⁺ efflux. Thus, the results of these in vitro experiments demonstrate that lobeline inhibits the effects of S(−)-nicotine, and suggest that lobeline acts as a nicotinic receptor antagonist.     

Pharmacokinetics of thrombin-like enzyme from venom of Agkistrodon halys ussuriensis Emelianov determined by ELISA in the rat.

A thrombin-like enzyme (TLE) was separated and purified from the venom of a northeast Chinese snake Agkistrodon halys ussuriensis Emelianov. Experiments were performed in rats to determine the pharmacokinetic parameters following an intravenous (i.v.) or a subcutaneous (s.c.) injection of the thrombin-like enzyme. The plasma levels of TLE were estimated by enzyme-linked immunosorbent assay. The method exhibited high reproducibility and accuracy in correlating optical densities with TLE concentrations (0.2–30 ng ml⁻¹, r=0.99). The plasma concentration-time course after i.v. administration of 50 μg kg⁻¹ TLE was well fitted by a two-compartment open model. The half-life of the -phase was 18.0±3.2 min, and that of the β-phase 3.9±0.7 h. The apparent volume of distribution was 1.8±0.5 l kg⁻¹, and clearance was 5.4±0.5 ml min⁻¹ kg⁻¹. When the TLE was injected s.c. at a dose of 0.75 mg kg⁻¹, the changes in plasma concentration were best described by a two-compartment model with a first-order absorption. The maximal plasma level of 51±2.7 ng ml⁻¹ was reached at 5.2±0.5 h. The absorption rate constant was 0.3±0.03 h⁻¹. The area under the plasma concentration-time curve (AUC) was 2.8±0.8 μg h⁻¹ ml⁻¹.     

Stability-indicating methods for the determination of sumatriptan succinate

Four stability-indicating methods were developed for the determination of sumatriptan succinate in the presence of its degradation products. The first method depends on the quantitative densitometric evaluation of thin-layer chromatography of sumatriptan succinate in the presence of its degradation products without any interference. Cyclohexane–dichloromethane–diethylamine (50:40:10 v/v/v) was used as a mobile phase and the chromatogram was scanned at 228 nm. This method determines sumatriptan succinate in the concentration range l–8 μg per spot with mean percentage recovery 100.52±1.23%. The second and third methods depend on the use of first-derivative (D₁) and second-derivative (D₂) spectrophotometry at 234 and 238 nm, respectively. These methods determine the drug in the concentration range 1.25–10 μg ml⁻¹ with mean percentage recovery 99.91±1.01% and 99.96±1.13% for (D₁) and (D₂), respectively. The fourth method depends on the use of ratio derivative spectrophotometric technique. The amplitude in the first derivative of the ratio spectra at 235 nm was selected to determine the cited drug in the presence of its degradation products. Calibration graph is linear in the concentration range 1.25–10 μg ml⁻¹ with mean percentage recovery 100.19±1.19%. The suggested methods were successfully applied for determining sumatriptan succinate in bulk powder, laboratory-prepared mixtures and pharmaceutical dosage forms (Imigran tablet) with good accuracy and precision. The results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by the reported method.     

Spectrophotometric determination of alendronate in pharmaceutical formulations via complex formation with Fe(III) ions

The formation of the complex between alendronate, non-chromophoric bisphosphonate drug important for the treatment of a variety of bone diseases, and iron(III) chloride in perchloric acid solution was studied. The stoichiometric ratio of alendronate to Fe(III) ions in the chromophoric complex was determined to be 1:1. The conditional stability constant was log K′_ave=4.50 (SD=0.15), indicating that the Fe(III)–alendronate complex is a complex of medium stability. The optimum conditions for this reaction were ascertained and a spectrophotometric method was developed for the determination of alendronate in the concentration range 8.1–162.5 μg ml⁻¹, the detection limit being 2 μg ml⁻¹. The method was validated for the direct determination of alendronate in tablet dosage formulations.     

LC determination of dinitrosopiperazine in simulated gastric juice

A simple and specific reversed phase HPLC method for the determination of dinitrosopiperazine in simulated gastric juice using UV detection was reported. The chromatographic resolution of the analyte and the internal standard isosorbide dinitrate was performed without extraction from the gastric juice on a reversed phase ODS column. Isocratic elution was carried out with methanol–0.02 M sodium dihydrogen phosphate (60:40 v/v, pH 3.0) at a flow rate of 1.0 ml min⁻¹ with UV detection at 238 nm. The calibration graph was linear over the concentration range 0.072–2.88 μg ml⁻¹ of dinitrosopiperazine with minimum detectability (S/N=2) of 0.01 μg ml⁻¹ (8×10⁻⁸ M). Inter-day and intra-day precisions calculated as% RSD were in the range 0.32–0.38% and 0.19–0.25% respectively. Inter-day and intra-day accuracies calculated as% error were in the range 0.18–0.21 and 0.08–0.11% respectively. The proposed method was successfully applied to the study of the possible in–vivo production of DNPZ under the standard nitrosation conditions recommended by WHO.     

Determination of some aminobenzoic acid derivatives: glafenine and metoclopramide

Simple, sensitive and accurate spectrophotometric methods for the determination of glafenine and metoclopramide hydrochloride are described. The first method is based on the oxidation of glafenine with iodic acid in strong acid medium to give a coloured diphenylbenzidine derivative and subsequent measurement of the coloured product at 509 nm. Beer's law is obeyed over the concentration range 2.5–20 μg ml⁻¹. The second method depends on the interaction of metoclopramide hydrochloride with p-dimethylaminocinnamaldehyde, to give a red coloured schiff's base with an absorbance maximum at 548 nm. Obedience to Beer's law is achieved over the concentration range 5–30 μg ml⁻¹. First-derivative method is used to overcome the slight interference of p-dimethylaminocinnamaldehyde reagent blank at the wavelength of measurement. Linearity between the peak heights at 576 nm versus concentration range 5–25 μg ml⁻¹ metoclopromide hydrochloride is obtained. The proposed methods have been successfully applied to the determination of these drugs in commercial products without interference. The validity of the methods is assessed by applying the standard addition technique, the relative standard deviation is less than 1%. The proposed methods are compared with reference methods with good agreement.