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Developing Countries↗
Biomedical subjects
H Zia
Publications and source records attributed to H Zia.
(N-stearyl, norleucine17) VIP hybrid inhibits the growth of pancreatic cancer cell lines.
The effects vasoactive intestinal peptide (VIP) antagonists were investigated on pancreatic cancer cell lines. (N-Stearyl, Norleucine17) VIP hybrid ((SN)VIPhyb) inhibited 125I-VIP binding to human Capan-2 cells with an IC50 value of 0.01 microM whereas VIP hybrid had an IC50 value of 0.2 microM. By RT-PCR and Northern blot, VPAC1 receptor mRNA was detected in CAPAN-2 cells. One microM (SN)VIPhyb and 10 microM VIPhyb inhibited the ability of 30 nM VIP to elevate cyclic AMP and increase c-fos mRNA. (SN)VIPhyb, 1 microM inhibited the clonal growth of CAPAN-2 cells in vitro. In vivo, (SN)VIPhyb (10 microg/day s.c.) inhibited CAPAN-2 xenograft growth in nude mice. These results indicate that (SN)VIPhyb is a pancreatic cancer VPAC receptor antagonist.
Amino Acid Sequence↗
Codiffusion of propylene glycol and dimethyl isosorbide in hairless mouse skin.
The in vitro percutaneous fluxes of propylene glycol (PG), cis-oleic acid (OA) and dimethyl isosorbide (DI) were determined and their effect on nifedipine (N) flux and lag time evaluated. PG, OA and DI flux through hairless mouse (HM) skin was measured in vitro by beta-scintigraphy and N permeation was measured by HPLC under finite and infinite dose conditions. Evaluation of each of the solvents separately showed that pure DI possessed the inherent ability to traverse the skin (12% in 24 h). For the tested formulation after 24 h, 57% of the PG and 40% of the DI had permeated across the skin with nearly linear permeation between 4 and 18 h and the relative order of permeation was PG > DI > N. DI permeation was further aided in the presence of PG and OA. N flux was dependent on concomitant solvent permeation. Over a 24-h test period a dose dependent response was observed for N, with 4.9-15.6 mg of N delivered from the lowest and highest doses, respectively, and the highest dose yielding zero-order flux of 146 (g/h per cm2).
Animals↗
Ophthalmic drug delivery systems--recent advances.
Eye-drops are the conventional dosage forms that account for 90% of currently accessible ophthalmic formulations. Despite the excellent acceptance by patients, one of the major problems encountered is rapid precorneal drug loss. To improve ocular drug bioavailability, there is a significant effort directed towards new drug delivery systems for ophthalmic administration. This chapter will focus on three representative areas of ophthalmic drug delivery systems: polymeric gels, colloidal systems, cyclodextrins and collagen shields. Hydrogels generally offer a moderate improvement of ocular drug bioavailability with the disadvantage of blurring of vision. In situ activated gel-forming systems are preferred as they can be delivered in drop form with sustained release properties. Colloidal systems including liposomes and nanoparticles have the convenience of a drop, which is able to maintain drug activity at its site of action and is suitable for poorly water-soluble drugs. Among the new therapeutic approaches in ophthalmology, cyclodextrins represent an alternative approach to increase the solubility of the drug in solution and to increase corneal permeability. Finally, collagen shields have been developed as a new continuous-delivery system for drugs that provide high and sustained levels of drugs to the cornea, despite a problem of tolerance. It seems that new tendency of research in ophthalmic drug delivery systems is directed towards a combination of several drug delivery technologies. There is a tendency to develop systems which not only prolong the contact time of the vehicle at the ocular surface, but which at the same time slow down the elimination of the drug. Combination of drug delivery systems could open a new directive for improving results and the therapeutic response of non-efficacious systems.
Animals↗
Breast cancer growth is inhibited by vasoactive intestinal peptide (VIP) hybrid, a synthetic VIP receptor antagonist.
Breast cancer vasoactive intestinal peptide (VIP) receptors were characterized. Using in vitro autoradiographic techniques, 125I-labeled VIP bound with high affinity to breast biopsy sections. 125I-labeled VIP bound specifically to give breast cancer cell lines examined using receptor-binding techniques. Specific 125I-labeled VIP binding to MDA-MB-231 cells was inhibited with high affinity by VIP and pituitary adenylate cyclase-activating polypeptide (IC50, = 2 nM) and with moderate affinity by the VIP hybrid (IC50 = 0.5 microM). VIP elevated the cAMP in a dose-dependent manner, and VIP hybrid (10 microM) inhibited the increase in cAMP caused by VIP. Using Northern blot analysis, VIP (10 nM) stimulated c-fos and c-myc mRNA, and the increase caused by VIP was reversed by the VIP hybrid. The VIP hybrid inhibited breast cancer growth in vitro and in vivo using nude mice bearing breast cancer xenografts. These data suggest that the VIP hybrid is a breast cancer VIP receptor antagonist.
Animals↗
Development of a new non-surgical perfusion technique for evaluation of nasal drug delivery.
A new non-surgical perfusion technique was developed to evaluate nasal absorption using the rabbit as an animal model and insulin as a model drug. For these studies 20 ml of insulin solution (10 U/kg + 0.05% Na taurocholate) was perfused for 3.5 hours at a rate of 10 ml/hr. Spray formulations containing different levels of insulin (1.25, 2.5, 5 and 10 U/kg) and sodium taurocholate (0.05 and 1.0%) were evaluated in the same animal model. Insulin loaded polyacrylic acid microparticles were administered in 1% gel formulation to determine the comparative effect of insulin. The absorption of insulin was measured by glucose reduction. Pharmacodynamic parameters were determined relative to subcutaneously injected insulin (0.25 U/kg). The new non-surgical perfusion technique proved to be easier to control and more reproducible than the formerly used perfusion model while providing comparable results. The maximum relative absorption was observed for the 1.25 U/kg spray containing 1% NaTC. The polyacrylic acid gel formulation containing insulin loaded microparticles (10 U/kg) resulted in lower hypoglycemic effect compared to the spray formulations and subcutaneous injection.
Administration, Intranasal↗
Cosolvency of dimethyl isosorbide for steroid solubility.
Dimethyl isosorbide (DMI), which is currently under investigation for its potential use as a pharmaceutical vehicle and drug permeation enhancer, is a water-miscible liquid with relatively low viscosity. The solubilization behavior of DMI as a cosolvent for nonpolar drugs was characterized via dielectric constant measurements of binary solvent systems containing DMI and either water, propylene glycol (PG), or polyethylene glycol (PEG). Evidence from the dielectric constant profiles and NMR studies suggest that DMI undergoes complexation with water and PG, but not with PEG, through hydrogen bonding interactions. The solvent complexation exhibited a major effect on the solubilities of prednisone, dexamethasone, and prednisolone in the mixed solvent systems. Maximum solubility of each drug was found to occur near a DMI/water or DMI/PG concentration ratio of 1:2. In the DMI-PEG mixed system, while there is no apparent interaction between DMI and PEG molecules, the solubility of prednisone was found to increase with decreasing dielectric constant.
Dexamethasone↗
Chromatographic analysis of griseofulvin and metabolites in biological fluids.
A simple and accurate assay for the determination of griseofulvin and its metabolites in biological fluids using high-performance liquid chromatography is described. Using a reversed phase column and a mobile phase solvent of 45% acetonitrile in 0.1 M acetic acid, baseline separation of griseofulvin and several analogues was obtained. The described method allows one to quantitatively determine griseofulvin, 6-demethylgriseofulvin, and griseofulvic acid, a newly identified metabolite in man, in urine and plasma samples. Treatment of plasma samples prior to the analysis is simply made by deproteinizing the samples with an equal volume of acetonitrile. For urine samples, the procedure involves diethyl ether extraction with subsequent evaporation to dryness and reconstitution with the mobile phase solvent.
Chromatography, High Pressure Liquid↗
Identification of griseofulvic acid as a urine metabolite of griseofulvin in humans.
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Biotransformation↗
Correlation of aspirin excretion with parameters from different dissolution methods.
The cumulative urinary excretion of four different aspirin products (two tablets, a capsule, and a timed-release tablet) was determined in a crossover study using five subjects. Comparison of in vivo results showed a significant difference in cumulative urinary excretion levels at only 1 hr. The excretion from the two regular tablets was significantly different from the timed-release tablet, but the capsule showed no significant difference from the other three products. Each product was tested in the USP, Levy beaker, and the regular and large magnetic basket dissolution apparatus. Analysis of variance of the in vitro results showed a significant difference between the aspirin products and the dissolution methods at selected times. In vitro comparison with in vivo results for the four products showed that a regression analysis can be used to determined which dissolution methods produce a significant correlation with urinary excretion.
Adult↗
In vivo and in vitro availability of commercial vitamin C tablets.
In vitro release of vitamin C from commercial tablets of three different manufacturers was measured by the Levy beaker, a modified USP basket and Magnetic Basket techniques and this was correlated with urinary excretion of the drug from normal, healthy, human males of 23 to 25 years of age weighing 50-72 Kg. Results showed that there was dissolution variability between the different brands of vitamin C tablets as well as between the in vitro dissolution methods used. There was also an inverse correlation between the time of in vitro release and the percent vitamin C excreted at the end of 2 hours. However, at the end of 24 hours the most rapidly dissolving tablets in vitro indicated only 66 percent excretion of the vitamin C as compared with nearly 83 percent for the slow dissolving types. It is concluded that to determine the total drug from a particular formulation, only disintegration and/or dissolution is not a good measure for an unstable and relatively rapid dissolving substance such as vitamin C. It is further suggested that perhaps if unstable rapid-dissolving substances were made more slowly released by formulation, a greater quantity of the drug would be physiologically avaiable.
Adult↗
Binding study of tetracyclines to human serum albumin using difference spectrophotometry.
The binding of several tetracyclines to human serum albumin was studied using difference spectrophotometry and a spectrophotometric probe, 2-(4'-hydroxybenzeneazo)benzoic acid. Difference spectra observed for the interaction between the probe and human serum albumin were similar to probe-bovine serum albumin spectra but were less intense for a given concentration of probe and did not reach saturation as quickly. Difference spectra for the tetracyclines were dependent on the characteristics of the ring substituents. More hydrophobic substituents on the D and C rings tended to give more intense difference spectra, but charge-transfer complexing may also have been involved since methacycline with a methylene group in the 6-position showed the most intense spectra of the compounds studied. Solvent perturbation, pH, and urea studies tended to confirm that something other than hydrophobic binding of the tetracyclines was involved. Drug-probe displacement studies showed that methacycline gave the greatest probe displacement followed by doxycycline, chlortetracycline, oxytetracycline, and tetracycline. This order of displacement of the anionic probe indicates that both hydrophobic and charge-transfer binding are involved. Experiments with calcium ion and ethylenediaminetetraacetic acid showed that the difference spectra obtained with the tetracyclines and human serum albumin were not the result of metallic bridge-chelate formation.
Calcium↗
Binding study of sulfonylureas and phenothiazines to bovine serum albumin using difference spectrophotometry.
2-(4'-Hydroxybenzeneazo)benzoic acid is a spectrophotometric probe which shows absorption spectrum changes upon binding to protein. Difference absorption spectra of this probe were used as an indirect measurement of the binding of selected sulfonylurea and phenothiazine drugs to bovine serum albumin. The results obtained using the spectrophotometric probe were similar to data obtained from other methods, especially fluorescent methods. Of the four sulfonylureas studied, tolbutamide showed the highest binding affinity, followed by glyburide, glipizide, and acetohexamide, in that order. The data collected for phenothiazine drugs indicated that chlorpromazine has the highest affinity, followed in order by trifluoperazine, perphenazine, fluphenazine, and promazine. Correlation of these results with chemical composition indicated that the interaction of phenothiazine drugs with bovine serum albumin was of a hydrophobic nature.
Animals↗
Competitive binding of two sulfas and penicillin G to bovine serum albumin using NMR techniques.
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Magnetic Resonance Spectroscopy↗
In vitro binding study of epinephrine and bovine serum albumin.
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Binding Sites↗
Development and evaluation of nasal formulations of ketorolac.
Ketorolac tromethamine is a potent non-narcotic analgesic with moderate anti-inflammatory activity. Clinical studies indicate that ketorolac has a single dose efficacy greater than morphine for postoperative pain and has excellent applicability in the emergency treatment of pain. Due to incomplete oral absorption of ketorolac, several approaches have been tried to develop a nonoral formulation in addition to injections, especially for the treatment of migraine headache. The aim of our study was to develop a nasal formulation of ketorolac with a dose equivalent to the oral formulation. A series of spray and lyophilized powder formulations of ketorolac were administered into the nasal cavity of rabbits, and their pharmacokinetics profiles were assessed. The spray and powder formulations were compared through their pharmacokinetics parameters and absolute bioavailability. Drug plasma concentration was determined using solid phase extraction, followed by an HPLC analysis. Nasal spray formulations were significantly better absorbed than powder formulations. A nasal spray formulation of ketorolac tromethamine showed the highest absorption with an absolute bioavailability of 91%. Within 30 min of administration, the plasma concentration was comparable to that resulting from an intravenous injection. The absolute bioavailability of a solution of ketorolac acid was 70%. Apparently, the dissolution of ketorolac acid into the mucous layer limits its absorption. There were no significant differences in absorption between different powder formulations. Even the reduction of particle size from 123 microm to 63 microm did not indicate better absorption of ketorolac tromethamine from powder formulations. Interestingly, the absolute bioavailability of ketorolac tromethamine from a powder formulation is only 38%, indicating that the drug may not be totally released from the polymer matrix before it is removed from nasal epithelium by mucociliary clearance.
Administration, Intranasal↗
Evaluation of polyvinyl acetate dispersion as a sustained release polymer for tablets.
Kollicoat SR 30D is a unique 30% aqueous dispersion of polyvinvyl acetate stabilized by polyvinyl-pyrrolidone intended for preparation of sustained release products. Detailed evaluation of this polymer dispersion as a sustained release coating for active pharmaceutical ingredients of two diverse classes of drugs was studied. A water insoluble drug (ibuprofen) and a water soluble drug (ascorbic acid) were selected as model active drugs. Ibuprofen was granulated using a GPCG-1 fluid bed processor prior to tableting, to improve the particle size and particle flow properties. In this process a 2(3) factorial design was implemented to evaluate the optimum process parameters such as spray rate, inlet air temperature and the inlet air velocity. The statistical model selected was Y(ijkl) = mu + tau(i) + beta(j) + theta(k) + (taubeta)ij + (betatheta)jk + (tautheta)ik + (taubetatheta)ijk + epsilon(ijkl). The factorial design showed that the spray rate, inlet air temperature, and inlet air velocity had a significant effect (p value <0.05) on the particle size. Significant improvement was observed in the flow properties of the granules. The granules were coated with Kollicoat SR30D dispersion using top spray method in the fluid bed processor. The dissolution studies showed that the release of ibuprofen decreased with an increase in the coating levels of Kollicoat SR 30 D. In the case of ascorbic acid, preparation of sustained release coated commercial granules was not possible due to the difficulty in coating a highly soluble drug particle. However, the coated granules when compressed into tablets showed some sustainability. Ibuprofen tablets manufactured with coated granules with a 15 g polymer for 300 g batch showed dissolution parameters of t50 and t90 at 4.2 hr and 7.5 hr, respectively. An approximate zero-type of release was observed when the polymer content was increased to 45 g for 300 g batch. Ascorbic acid tablets made with coated commercial granules having a total polymer content of 45 g per a 500 g batch showed an average dissolution t50 and t90 at 1.0 hr and 4.55 hr, respectively. When the total polymer content was increased to 60 g, per 500 g, the average dissolution t50 and t90 delayed to 1.40 hr and 7.20 hr, respectively.
Analysis of Variance↗