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At least 919 records · Page 51Linked to original sources
PubMed2006

Development and application of spectrophotometric methods for the determination of citalopram hydrobromide in dosage forms.

Study was carried out to develop two simple, fast, accurate and sensitive spectrophotometric methods (A and B) for the determination of citalopram hydrobromide in commercial tablet formulations. In method A, UV spectrophotometer determined the contents of citalopram hydrobromide in tablets at 240 nm in methanol solvent. The linear range was 5-40 microg ml-1 with molar absorptivity 1.4x10(4) l mol-1 cm-1. While the method B based on the reaction of citalopram base as n-electron donor with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone as pi-acceptors to give highly colored complex species that absorb maximally at 590 nm. Beer's law was obeyed in the concentration limit of 10-250 microg ml-1 with molar absorptivity 3.3x10(3) l mol-1 cm-1 for citalopram hydrobromide. The limits of detection and limit of quantification was calculated and found to be 5.2 microg ml-1 and 17.4 microg ml-1 respectively. The proposed methods were found to be rapid, accurate, precise and sensitive for the determination of citalopram hydrobromide in commercial tablet formulations with out interferences from common additives encountered.

Antidepressive Agents, Second-Generation↗
PubMed2002

Antitumor activities of conjugates of mitomycin C with estradiol benzoate and estradiol via glutaric acid in suspension dosage form.

Conjugates of mitomycin C (MMC) with estradiol bezoate and estradiol via glutaric acid (EB-glu-MMC and E-glu-MMC, respectively) were examined for their antitumor activities against P388 leukemia and sarcoma 180. EB-glu-MMC and E-glu-MMC were suspended in 10% (v/v) propylene glycol in saline and administered intraperitoneally to mice bearing P388 leukemia intraperitoneally or to mice bearing sarcoma 180 subcutaneously. The antitumor effect against P388 leukemia was greater in the order MMC>E-glu-MMC>EB-glu-MMC, and only the former two compounds significantly increased life span. On the other hand, EB-glu-MMC and E-glu-MMC showed suppression of sarcoma 180 growth at higher doses close to or better than MMC. In the mixture of 1/15 M phosphate buffer (pH 7.4, ionic strength (mu) adjusted to 0.3 with NaCl)-propylene glycol (9:1, v/v) at 37 degrees C, MMC was released much more slowly from EB-glu-MMC suspension than from E-glu-MMC suspension. With regard to chemotherapy against sarcoma 180, both conjugates were considered to supply MMC slowly but effectively at higher doses.

Animals↗
PubMed2002

Voltammetric determination of josamycin (a macrolide antibiotic) in dosage forms and spiked human urine.

The voltammetric behaviour of josamycin (a macrolide antibiotic) has been studied using direct current (DC(t)) alternating current (AC(t)) and differential pulse polarography (DPP). In Britton-Robinson buffers, josamycin developed cathodic waves over the pH range 7-12. At pH 10, a well-defined cathodic wave with diffusion current constant of 1.06 +/- 0.19 (n = 5) was obtained. The wave was characterized as being diffusion-controlled; and partially affected by adsorption phenomenon. The current-concentrations plots are rectilinear over the range 10-60 and 6-50 microg/ml using DC(t) mode and DPP mode, respectively. The minimum detectability limit was 1.2 microg/ml (1.9 x 10(-6) M) adopting the DPP mode. A method was proposed for the determination of josamycin in its tablets adopting both DC(t) and DPP modes. The results obtained were in good agreement with those given by the manufacturer. The method was extended to the in-vitro determination of the drug in spiked human urine; the % recovery was 98.06 +/- 1.76% (n = 5). The number of electrons involved in the reduction process was accomplished and a proposal of the electrode reaction was presented.

Anti-Bacterial Agents↗
PubMedDate not supplied

Development of mucoadhesive dosage forms of buprenorphine for sublingual drug delivery.

The development of mucoadhesive formulations of buprenorphine for intended sublingual usage in the treatment of drug addiction is described. The formulations include mucoadhesive polymer films, with or without plasticizers, and mucoadhesive polymer tablets, with or without excipients that enhance drug release and/or improve tablet compaction properties. The mucoadhesive polymers studied include carbomers such as Carbopol 934P, Carbopol 974P, and the polycarbophil Noveon AA-1, with excipients chosen from pregelatinized starch, lactose, glycerol, propylene glycol, and various molecular weights of polyethylene glycol. The development of plasticizer-containing mucoadhesive polymer films was feasible; however, these films failed to release their entire drug content within a reasonable period. Thus, they were not determined suitable for sublingual usage because of possible loss by ingestion during routine meal intakes. The mucoadhesive strength of tablet formulations containing Noveon AA-1 appears to be slightly superior to the Carbopol-containing tablets. However, the Carbopol 974P formulations exhibited superior drug dissolution profiles while providing adequate mucoadhesive strength. The tablet formulations containing Carbopol 974P as mucoadhesive polymer, lactose as drug release enhancer, and PEG 3350 as compaction enhancer exhibited the best results. Overall, the mucoadhesive tablet formulations exhibited superior results compared with the mucoadhesive film formulations.

Adhesives↗
PubMed2000

Application of a sensorial response model to the design of an oral liquid pharmaceutical dosage form.

In this paper, we discuss the application of a compartmental model to study the sensorial response, in terms of taste intensity versus time, in an oral solution for pharmaceutical use. The numerical model was developed from sensorial response curves obtained by a panel of three trained individuals. Parameter identification was carried out by means of a least-squares procedure that obtained the linear coefficients in the model by solving an exact linear least-squares problem conditional on the values of the nonlinear parameters for each iteration. Thus, nonlinear estimation was done in terms of the first-order kinetic parameters only, and ill-conditioning of the Hessian matrix present in these models was solved. Results of modeling for a set of formulations were used to determine the effects of various ingredients (sweeteners and an essence) on a baseline unflavored formulation of acetaminophen in a mixture of cosolvents. The first moment of the area under the curve of taste intensity versus time was found to be the best global indicator of taste for the purpose of product design. It was found that a mixture of sweeteners and an essence was the most efficient way of masking the bitter taste of this active ingredient.

Acetaminophen↗
PubMed2000

Multimechanism oral dosage forms fabricated by three dimensional printing.

Four types of complex oral drug delivery devices have been fabricated using the three dimensional printing process. Immediate-extended release tablets were fabricated which were composed of two drug-containing sections of different pH-based release mechanisms. Pulsed release of chlorpheniramine maleate occurred after a lag time of 10 min followed by extended release of the compound over a period of 7 h. Breakaway tablets were fabricated composed of three sections. An interior fast-eroding section separating two drug-releasing sub-units eroded in 30-45 min in simulated gastric fluid. Enteric dual pulsatory tablets were constructed of one continuous enteric excipient phase into which diclofenac sodium was printed into two separated areas. These samples showed two pulses of release during in vitro USP dissolution at 1 and 8 h with a lag time between pulses of about 4 h. Dual pulsatory tablets were also fabricated. These samples were composed of two erosion based excipient sections of opposite pH based solubility. One section eroded immediately during the acid dissolution stage releasing diclofenac during the first 30 min, and the second section began eroding 5 h later during the high pH stage.

Delayed-Action Preparations↗
PubMed2002

A simple kinetic spectrophotometric method for the determination of isoxsuprine in dosage forms.

A simple and sensitive kinetic method was developed for the determination of isoxsuprine in pharmaceutical preparations. The method is based upon a kinetic investigation of the oxidation reaction of the drug with alkaline potassium permanganate at room temperature for a fixed time of 30 min. The absorbance of the coloured manganate ion was measured at 610 nm. Alternatively, the decrease in the absorbance of potassium permanganate after addition of the drug was measured at 525 nm. The absorbance-concentration plots in both procedures were rectilinear over the range of 0.5-4 microg ml(-1) (r = 0.9998) with a minimum detectability of 0.05 microg ml (-1) (1.48 x 10(-7) M). The different experimental parameters affecting the development and stability of the colours were carefully studied and optimized. The determination of isoxsuprine by the fixed concentration and rate constant methods is also feasible with the calibration equations obtained but the fixed time method has been found to be more applicable. Both procedures were applied to the determination of isoxsuprine in formulations. The results obtained were in good agreement with those obtained using a reference method. The proposed method was also adopted to detect isoxsuprine in spiked human plasma at its therapeutic level of concentration (0.4 microg ml(-1)). A proposal of the reaction pathway was postulated.

Dosage Forms↗
PubMed2004

In vitro analysis of rifampicin and its effect on quality control tests of rifampicin containing dosage forms.

The chemical stability of rifampicin both in solid state and various media has widely been investigated. While rifampicin is appreciably stable in solid-state, its decomposition rate is very high in acidic as well as in alkaline medium and a variety of decomposition products were identified. The literature reports on highly variable rifampicin decomposition in acidic medium. Hence, the objective of this investigation was to study possible reasons responsible for this variability. For this purpose, filter validation and correlation between rifampicin and its degradation products were developed to account for the loss of rifampicin in acidic media. For analysis of rifampicin with or without the presence of isoniazid, a simple and accurate method was developed using high performance chromatography recommended in FDC monographs of the United States Pharmacopoeia. Using the equations developed in this investigation, the amount of rifampicin degraded in the acidic media was calculated from the area under curve of the degradation products. Further, it was proved that in a dissolution study, the colorimetric method of analysis recommended in the United States Pharmacopoeia provides accurate results regarding rifampicin release. Filter type, time of injection as well as interpretation of data are important factors that affect analysis results of rifampicin in in vitro studies and quality control.

Antibiotics, Antitubercular↗
PubMed1987

Computer-aided dosage form design. I. Methods for defining a long-acting first-order delivery system of maximum formulating flexibility.

The method provides an a priori assessment of the maximum allowable flexibility in the rate of release from a prolonged-release formulation. The clinical pharmacokinetic parameters describing the drug candidate are employed to calculate the ranges of rate constants and doses required for the formulation to provide a selected therapeutic duration. For a given patient, there may be an infinite number of combinations of release rate constants and dose sizes which will maintain steady-state plasma drug concentrations within a desired range when the formulation is administered at the selected dosing interval. Computer simulations of steady-state plasma concentrations are employed to establish the ranges for all of the acceptable rate constants and doses for each member of a group. The entire group is then examined to define the range of release rate constants and doses which would provide a useful formulation for every member in the group. Literature values for theophylline clinical pharmacokinetics in children and adults have been employed to illustrate the application of this method. The method is unique in that it provides an entire range of release rates on which to gauge the feasibility for success.

Administration, Oral↗
PubMed2004

Companion animal physiology and dosage form performance.

Among the most critical parameters for any drug candidate are tolerability, dose, solubility and permeability. For controlled release formulations, gastrointestinal transit is an added hurdle. While we might assume that intestinal transit is independent of the drug candidate, the relative importance of gastrointestinal transit time (GITT) depends directly on the other parameters. For example, a formulation of a drug with low solubility (LS) and/or low permeability (LP) characteristics might provide the required systemic concentrations when administered with food, but not if administered on an empty stomach. In the LS case, the drug may require the solubilizing effects of increased fluid and bile salts that accompany the meal. Likewise, a controlled release formulation of a drug with a region of preferred absorption may empty from the fasted stomach and move beyond the region before drug release is complete. Companion animals (e.g. cats and dogs) differ from humans and each other with respect to GITT, food effects, eating habit influences, breed and size variability, gastric pH, intestinal enzymes, GI permeability and absorption regions. This review examines how the anatomy and physiology of companion animals relates to the performance of orally administered immediate and controlled release formulations. Examples are presented of techniques used to predict the dose and acceptable solubility of drug candidates, and the performance of formulations in companion animals.

Administration, Oral↗
PubMedDate not supplied

Diffusion of preservatives from topical dosage forms: a comparative study.

A study of the diffusion of parabens from topical formulations is presented here. In particular, four different topical formulations, namely, a water-in-oil emulsion, an oil-in-water emulsion, and two hydrophilic gels (Pemulen gel and Carbopol gel) were produced, containing a mixture of three common parabens, namely, methylparaben (MP), ethylparaben (EP), and propylparaben (PP). An analytical method based on liquid extraction, followed by reversed-phase HPLC for the quantitative determination of MP, EP, and PP, was developed. The method allowed good separation of paraben mixtures and high percentages of recovery (> than 97%). The diffusion kinetics of parabens from the produced formulations was determined by an in vitro system based on a Franz cell assembled with a synthetic membrane, followed by a reversed-phase HPLC analytical method. The comparative study demonstrated that, in the case of emulsions, diffusion coefficients are a function of the substituent of preservatives: the higher the solubility, the higher the diffusion of parabens. On the contrary, in the case of the hydrophilic gels, the higher the parabens solubility, the lower the diffusion coefficients. The method described here could represent a means of controlling the extent of diffusion of parabens from topical formulations in order to minimize percutaneous absorption and to control the availability of microbes.

Chromatography, High Pressure Liquid↗
PubMed2004

Once-daily propranolol extended-release tablet dosage form: formulation design and in vitro/in vivo investigation.

The purpose of this study was to develop and optimize the propranolol once-daily extended release formulations containing HPMC, Microcrystalline cellulose (MCC) and lactose. In vitro studies, the response surface methodology and multiple response optimization utilizing the polynomial equation were used to search for the optimal formulation with specific release rate at different time intervals. The constrained mixture experimental design was used to prepare systematic model formulations, which were composed of three formulation variables: the content of HPMC (X(1)) MCC (X(2)) and lactose (X(3)). The drug release percent at 1.5, 4, 8, 14 and 24 h were the target responses and were restricted to 15-30, 35-55, 55-75, 75-90 and 90-110%, respectively. The results showed that the optimized formulation provided a dissolution pattern equivalent to the predicted curve, which indicated that the optimal formulation could be obtained using response surface methodology. The mechanism of drug release from HMPC matrix tablets followed non-Fickian diffusion. In the vivo study, the MRT was prolonged for matrix tablets when compared with commercial immediate release tablets. Furthermore, a linear relationship between in vitro dissolution and in vivo absorption was observed in the beagle dogs.

Administration, Oral↗
PubMed2002

Spectrofluorimetric determination of vigabatrin and gabapentin in urine and dosage forms through derivatization with fluorescamine.

A stability-indicating, sensitive, simple and selective spectrofluorimetric method was developed for the determination of vigabatrin (VG) and gabapentin (GB). The method is based on the reaction between the two drugs and fluorescamine in borate buffer of pH 8.2 to give highly fluorescent derivatives that are measured at 472 nm using an excitation wavelength of 390 nm for both drugs. The optimum conditions were ascertained and the method was applied for the determination of VG and GB over the concentration range of 0.20-4.00 and 0.1-1.0 microg/ml, respectively with detection limits of 0.05 microg/ml (2.9 x 10(-7) M) and 0.06 microg/ml (2.3 x 10(-7) M) for VG and GB, respectively. The suggested method was applied, without any interference from the excipients, to the determination of the two drugs in their pharmaceutical formulations. Furthermore, the method was extended to the in-vitro determination of both drugs in spiked human urine. Interference from endogenous amino acids could be eliminated through selective complexation with copper acetate, the % recovery (n=4) is 98.0 +/- 7.05. Co-administered drugs such as lamotrigine, phenobarbitone, valproic acid, clopazam, carbamazepine, clonazepam and cimitidine did not interfere with the assay. The method is also stability-indicating; as the degradation product of vigabatrin: 5-vinylpyrrolidin-2-one, produced no interference with its analysis.

Acetates↗
PubMed2002

[An increase in serum phenytoin concentration by changes of dosage form: case reports and its mechanism].

Phenytoin (PHT) exhibits nonlinear pharmacokinetics in the therapeutic range. Therefore a slight increase in dose may lead to considerable elevation of the serum PHT level. Although its bioavailability is dependent on the formulation, bioequivalence is considered to be preserved between the three major formulations, of tablet, 97% fine granules, and 10% powder. However, we experienced many cases of increases serum PHT concentration after changes in formulation from 97% fine granules to 97/4% hospital-made fine granules, and from the latter to 10% powder. Retrospective analysis revealed that these alterations were accompanied by 55% and 16% increases in the serum concentration-to-dose ratio of PHT, respectively. We investigated the factors of this increase by analyzing the weight of remaining powder in a package and the PHT content of each formulation. Each package of PHT formulation prepared with 97% fine granules and 10% powder was unsealed, and the contents were weighed to calculate the rate of recovery. The rate of ingestion was estimated by correcting the rate of recovery by PHT strength (i.e., 1.0 for 10% powder and 0.97 for fine granules). The rates of recovery and ingestion for 10% powder were 13% and 16% higher than those for 97% fine granules, respectively (p < 0.01). In conclusion, Changing the PHT formulation from 97% fine granules to 10% powder may lead to a considerable increase in the serum PHT concentration and possibly induce PHT toxicity.

Adolescent↗
PubMed2006

Biowaiver monographs for immediate release solid oral dosage forms: acetaminophen (paracetamol).

Literature data are reviewed on the properties of acetaminophen (paracetamol) related to the biopharmaceutics classification system (BCS). According to the current BCS criteria, acetaminophen is BCS Class III compound. Differences in composition seldom, if ever, have an effect on the extent of absorption. However, some studies show differences in rate of absorption between brands and formulations. In particular, sodium bicarbonate, present in some drug products, was reported to give an increase in the rate of absorption, probably caused by an effect on gastric emptying. In view of Marketing Authorizations (MAs) given in a number of countries to acetaminophen drug products with rapid onset of action, it is concluded that differences in rate of absorption were considered therapeutically not relevant by the Health Authorities. Moreover, in view of its therapeutic use, its wide therapeutic index and its uncomplicated pharmacokinetic properties, in vitro dissolution data collected according to the relevant Guidances can be safely used for declaring bioequivalence (BE) of two acetaminophen formulations. Therefore, accepting a biowaiver for immediate release (IR) acetaminophen solid oral drug products is considered scientifically justified, if the test product contains only those excipients reported in this paper in their usual amounts and the test product is rapidly dissolving, as well as the test product fulfils the criterion of similarity of dissolution profiles to the reference product.

Acetaminophen↗
PubMed2002

Investigation of critical factors for the resolution of SR695, a key impurity, from efavirenz in the reversed-phase assay of efavirenz dosage forms.

An investigation of the critical factors effecting the resolution of SR695 from efavirenz in the assay of efavirenz by reversed-phase HPLC was performed. This study was implemented to address the inability of a subset of the Zorbax SB-CN columns used in this method to adequately perform this separation, which were otherwise indistinguishable from columns of this type that could. In this study, column temperature, detector time-constant, pre-gradient isocratic hold-time, pre-column mixing volume, column, and HPLC type were considered. Experimental Design methods were employed to find the relative importance of these factors and to find parameters that would optimize the resolution of SR695 and efavirenz on any HPLC, with any column of this type, for both efavirenz oral liquid and capsule samples. It was also desired that this method change be minimal, so that extensive revalidation would not be required. The most important factors were the column temperature, with lower temperatures giving better resolution, and pre-column mixing volume of sample with mobile phase, with higher mixing volumes giving better resolution up to an asymptote reached at around 150 microl. Added pre-gradient isocratic hold time was found to result in a small improvement in resolution, but was insignificant compared with the other factors mentioned above. A possible explanation is given for the mechanism by which temperature and pre-column mixing have this effect on the resolution obtained in this assay.

Alkynes↗
PubMed1978

Molecular interaction between E-prostaglandins and selected polymers and its potential utilization in oral dosage form design.

Coacervate formation was observed between some E-prostaglandins and povidone in acetonitrile. This molecular interaction was studied using differential scanning calorimetry, IR spectrophotometry, and light microscopy. The structural requirements for coacervate formation between E-prostaglandins and povidone were investigated. Possible utilization of this molecular interaction in the development of E-prostaglandin formulations was explored. The dissolution rate of some insoluble E-prostaglandin esters increased when they were coprecipitated with povidone and polyethylene glycol. For example, the p-hydroxybenzaldehyde semicarbazone ester of 16,16-dimethyldinoprostone dissolved about 200 times faster as a povidone coprecipitate than did the control mixture. Enhancement of the dissolution rate was observed for the povidone coprecipitates of dinoprostone and its p-acetylphenyl and beta-naphthyl exters but not for the p-phenylphenyl ester. Fast dissolving dispersions of the E-prostaglandin esters also could be prepared with the water-insoluble cross-linked polyvinylpyrrolidone. This type of dispersion was nonglassy and easily dispersible in water. Thus, it might have certain advantages over the classical soluble povidone coprecipitates in terms of ease of handling. The degree of enhancement in dissolution of dispersions of cross-linked polyvinylpyrrolidone and E-prostaglandin esters is apparently dependent on the structure of the esters. The potential dissolution enhancement may be related to the strength of the interaction between the macromolecule and the esters, as indicated by the qualitative relationship between the extent of adsorption of the prostaglandins to cross-linked polyvinylpyrrolidone and the dissolution rate enhancement.

Administration, Oral↗
PubMed2001

Different methods for the determination of gestodene, and cyproterone acetate in raw material and dosage forms.

Four new precise accurate and selective methods have been developed for the determination of gestodene (I) and cyproterone acetate (II). The first method (A) depends on reaction of (I) and (II) with isoniazide in an acid medium and the colored products were measured at 378 and 400 nm, respectively. The second method (B) depends on the reaction of (I) and (II) with tetrazolium blue in an alkaline medium and the colored products were measured quantitatively at 515 and 520 nm, respectively. The optimum conditions for the analysis were studied. Both methods determined gestodene (I) in concentration range from 4 to 24 microg ml(-1) with mean percentage recoveries 99.54%+/-1.20 and 99.63%+/-1.89 for method A and B, respectively. For cyproterone acetate, the concentration ranges were 4-36 and 8-40 microg ml(-1) with mean percentage recoveries 99.94%+/-1.19 and 99.23%+/-2.00 for methods A and B, respectively. The third method (C) depends on the quantitative evaluation of (I) and (II) densitometrically using dichloroethane:methanol:water (95:5:0.2) as mobile phase and the chromatogram were scanned at 247 and 281 nm, respectively. Method (C) determines (I) and (II) in concentration ranges from 0.2 to 1.6 and 0.1-0.7 microg microl(-1) using Hamilton syringe 10 microl, with mean percentage recoveries 99.94%+/-1.19, and 99.82%+/-1.75, respectively. The fourth method (D) is a first derivative one depends on measuring the D(1) value at 303 nm for (II) only in concentration range 10-20 microg ml(-1) with mean percentage recoveries 99.95%+/-1.49.

Acne Vulgaris↗