Simultaneous Spectrophotometric Estimation of Haloperidol and Trihexyphenidyl in Tablets

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Haloperidol (HP) is an antidyskinetic and antipsychotic drug whose IUPAC name is 4-[4-(4-chlorophenyl)-4-hydroxy-1-piperidyl]-1-(4fluorophenyl)-butan-1-one.Trihexyphenidyl (THP) is an antidyskinetic and antiparkinson drug whose IUPAC name is 1-cyclohexyl-1-phenyl-3-(1-piperidyl)-1-propanol.HP is offi cial in BP [1] and THP in IP [2] .BP suggests a titrimetric assay method for HP, while IP suggest a titrimetric assay method for THP.Literature survey revealed that HPLC methods [3,4] have been reported for the estimation of HP and THP individually and with other drugs in pharmaceutical dosage forms.However, no method is reported for the simultaneous estimation of these drugs in combined dosage forms.This prompted us to develop simple, rapid, accurate, economical and sensitive spectrophotometric method.Shimadzu 1700 UV/Vis spectrophotometer with matched cuvettes was used for the experimental work.The chemicals used were of analytical grade.Commercially available tablets of HP and THP in combination were procured from the local pharmacy.Standard HP and THP were received as gift samples from Stadmed Pvt. Ltd., Kolkata.
Standard stock solutions of HP and THP were prepared separately by dissolving 25 mg each of standard HP and THP in methanol and 0.1N HCl (90:10) and making up the volume to 50 ml with same solvent.Standard solutions (25 µg/ml) HP and THP were further prepared by taking 2.5 ml of stock solution of each drug in two 50 ml volumetric fl asks separately and making up the volume to the mark with same solvent.estimation of HP and THP.Twenty tablets were weighed and crushed to a fine powder.Powder equivalent to 50 mg of HP and 20 mg of THP (tablet contains 5 mg HP and 2 mg THP) was dissolved in the solvent and volume was made up to 50 ml.Insoluble excipients were separated by fi ltration.The fi ltrate was further diluted to get fi nal concentration of both the drugs in the linearity range.Absorbance was noted at the selected wavelengths and percent label claim was determined by using the Eqn., Percent label claim= (Cx or Cy×D×W)/(Wm×L)×100 where, Cx or Cy= concentration of HP or THP in g/100 ml, W= average weight of tablet, Wm= weight of sample taken and L= label claim of sample taken.
Reproducibility, repeatability and accuracy of the proposed method were found to be satisfactory which is evident from the low values of standard deviation (SD), percent relative standard deviation (RSD) and standard error (SE) (Table 1).The accuracy and reproducibility of the proposed method was confirmed by recovery experiment, performed by adding known amount of the drugs to the preanalyzed formulations and reanalyzing the mixture by proposed method (Table 2).Percent recovery obtained indicates non-interference from the excipients used in the formulation.Thus, the method developed in the present investigation is found to be simple, sensitive, accurate and precise and can be successfully applied for the simultaneous estimation of haloperidol and trihexyphenidyl in tablets.
Overlain spectra of standard solutions of HP and THP were obtained and scanned between 200-300 nm (fi g. 1).HP showed absorption maxima at 245.0 nm and THP showed at 206.0 nm.Calibration curve for each drug was prepared in the concentration range of 2.5-12.5 µg/ml for HP and 1.0-5.0µg/ml for THP at corresponding wavelengths i.e. 245.0 nm and 206.0 nm.Amount of each drug was determined using simultaneous Eqn. as Cx= (A 2 ay 1 -A 1 ay 2 )/(ax 2 ay 1ax 1 ay 2 ).Cy= (A 1 ax 2 -A 2 ax 1 )/(ay 1 ax 2 -ay 2 ax 1 ), where, Cx= concentration of HP in g/100 ml, Cy= concentration of THP in g/100 ml, A 1 = absorbance of laboratory mixture at 245.0 nm, A 2 = absorbance of laboratory mixture at 206.0 nm, ax 1 = absorptivity of HP at 245.0 nm, ax 2 = absorptivity of HP at 206.0 nm, ay 1 = absorptivity of THP at 245.0 nm and ay 2 = absorptivity of THP at 206.0 nm.Percent estimation= (C×D)/W×100, where, C= Cx or Cy= concentration of HP or THP in g/100 ml, D= dilution factor and W= weight of drug (either HP or THP) in the laboratory mixture.
Marketed tablets Halotex (Triton Health Care Pvt.Ltd., Chennai, India) were used for the simultaneous   Antioxidants are now standing on the mainstay of the treatment and prevention of several diseases [1][2][3] .Current research is directed towards fi nding naturally occurring antioxidants particularly of plant origin.Oroxylum indicum Vent.(Bignoniaceae), a rare endangered and threatened medicinal plant widely used traditionally for treating several disorders [4] .The root-bark is used as an astringent and tonic and also in diarrhoea and dysentery.The stem bark is used in acute rheumatism.
In the form of an infusion, it is used as a diaphoretic.The fruits are used as carminative and stomachic, while the seeds are used as purgative.The roots are used in dropsy and the leaves are reputed as an emollient.Tender fruits are described as carminative and stomachic [5] .The root of this plant is also one of the important ingredients in most commonly used ayurvedic formulations like dantyadyarista, brahma rasayana, dasamula, amartarista, dhanawantara ghrita, narayana taila [6] .The anti cancer potential of different parts of the plant has already been reported [7,8] .The present study describes a comparative evaluation of different parts of Oroxylum indicum for their in vitro antioxidant activity.
The different parts of the plant i.e. root, root bark, stem, stem bark, leaves and fruits were collected from the forest region of Orissa and identifi ed at the Institute of Materials and Minerals Technology, Bhubaneswar, Orissa.All the plant materials were shade dried, powdered, sieved and successively extracted with petroleum ether and methanol to obtain the extracts.The each of these extracts was concentrated in a rotary evaporator under reduced pressure, giving individual extracts.Ten milligrams of methanol extract of different parts was dissolved in methanol (1 ml) and solution was serially diluted for antioxidant studies.
Total polyphenolic compounds of different extracts were performed according to the method of Slinkard and Singleton [9] .DPPH radical scavenging activity [10] , nitric oxide scavenging assay [11] , superoxide