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At least 289 records · Page 16Linked to original sources
PubMed2000

Biopharmaceutical considerations in topical ocular drug delivery.

1. Despite the accessibility of the front of the eye, efficient delivery of drug to treat various ocular disorders is a challenge to the formulation scientist. The majority of ophthalmic medications are formulated as eye drops. Due to anatomical constraints, the volume that can be administered is limited to approximately 30 microL. This, together with the efficient clearance system that exists in the front of the eye, makes it difficult to maintain an effective pre-ocular drug concentration for a desired length of time. Various formulation strategies have been used to increase pre-ocular retention of eye drops. The most successful of these has been the inclusion of viscosity enhancing polymers, particularly those able to interact with the mucous layer on the eye surface or those that can undergo a transition from a solution to a gel under the conditions of the pre-ocular area. 2. When the target site is intra-ocular, drug must be absorbed from the pre-ocular region into the eye. The main route for absorption is across the cornea. However, absorption of drug across the cornea is inefficient due to its impermeable nature and small surface area. Thus, the intra-ocular bioavailability of topically administered medications is typically less than 10%. 3. Corneal permeability favours moderately lipophilic compounds. These compounds often have a low aqueous solubility. Problems in ocular drug delivery and formulation are compounded for poorly soluble drugs that must be formulated as suspensions. 4. Reformulation of ophthalmic suspensions as solutions has many advantages. This may be achieved by complexation using cyclodextrins. Solubilization using cyclodextrins can overcome many of the formulation problems. However, it is unclear as to their potential for improving ocular bioavailability, which is seemingly drug dependent and may be influenced by both the physicochemical properties of the drug and the complex formed.

Absorption↗
PubMed2005

In vivo biopharmaceutical characterisation of a new formulation containing the antiepileptic drug lamotrigine in comparison to plain and dispersible/chewable lamotrigine tablets.

AIM: Two studies in healthy male volunteers were carried out to evaluate the pharmacokinetic profile of a new divisible formulation of lamotrigine (CAS 84057-84-1, Plexxo, Lamotrigin Desitin) in plasma in comparison to plain or dispersible lamotrigine tablets. METHODS: The plasma pharmacokinetics of lamotrigine were analysed after administration of single doses of 100 mg lamotrigine given as one tablet of the new formulation and either the plain or the dispersible reference formulation in two separate studies. In each study the data of 24 subjects were analysed according to the study protocol. Venous blood samples were taken at appropriate intervals up to 120 h after dosing. Concentrations of lamotrigine were determined in plasma by a validated HPLC method using UV detection. RESULTS AND CONCLUSION: In both studies, mean plasma concentration-time profiles of the new lamotrigine formulation and both reference formulations ran nearly in parallel. The pharmacokinetic mean data calculated from different subject groups of the two studies were very similar. The mean ratios of the main pharmacokinetic parameters and the corresponding 90% confidence intervals of AUC(0-t), AUC(0-inf) and C(max) were 103% (99.7-105.7), 103% (99.6-107.3) and 101% (95.2-106.6) for the comparison with the plain lamotrigine tablet and 100% (98.0-102.8), 100% (96.5-102.8) and 102% (99.1-105.3) for the comparison with the dispersible/chewable tablet, respectively. The most frequently reported adverse events possibly related to the administration of lamotrigine were headache and dizziness in both studies. It is concluded that the new divisible lamotrigine formulation is bioequivalent with regard to rate and extent of absorption to both the plain reference lamotrigine product and to the dispersible/chewable reference product.

Adolescent↗
PubMedDate not supplied

The influence of stirring rate on biopharmaceutical properties of Eudragit RS microspheres.

Eudragit RS microspheres containing pipemidic acid, as a model drug, were prepared by the solvent evaporation method using an acetone/liquid paraffin solvent system. The aim of the work was to evaluate the influence of stirring rate on the average particle size, particle morphology, drug content and release kinetics, as well as the influence of particle size on microsphere morphology, drug content and release kinetics. Stirring rate has been found to significantly influence the average diameter of microspheres. The average diameter decreases as the stirring rate increases. This can be explained by production of a finer dispersion of droplets when higher stirring rates are applied and, consequently, by the formation of smaller microspheres. With increasing stirring rate and increasing fraction particle size the drug content also increases. It is assumed that this dependence is a consequence of an uneven diffusion of the drug from the inner to the outer emulsion phase, and an uneven encapsulation of drug particles during the preparation. Drug release follows the Higuchi model. As seen from SEM photographs, larger microspheres are more porous and the microspheres produced at higher stirring rates are more porous than those produced at lower stirring rates. This explains the unexpected finding that the release rate increases as the fraction particle size and the stirring rate increase.

Acrylic Resins↗
PubMedDate not supplied

Formulation and biopharmaceutical evaluation of osmotic matrix tablets of diclofenac sodium.

The objective of our study was to prepare and evaluate osmotic matrix (OM) tablets of diclofenac sodium (DS). In vitro studies were done on USPXXIV dissolution apparatus II in different release medium. Surface characteristics of coating films and osmotic contribution of OM tablets also were studied. In vivo evaluation was carried out in 6 healthy human volunteers using HPLC method to assay plasma samples, and the results were compared with the performance of fabricated matrix and two commercial tablets of DS. Through in vitro drug release kinetics, using regression coefficient analysis and Peppas equation, different pharmacokinetic parameters and relative bioavailability were determined. OM tablets were found to provide more prolonged and controlled therapeutic plasma DS levels and also showed improved bioavailability in comparison to fabricated matrix and commercial tablets studied.

Adult↗
PubMed1999

Design and biopharmaceutical evaluation of nitrofurantoin-loaded Eudragit RS100 micropellets.

Nitrofurantoin, a synthetic bactericidal drug, was encapsulated with Eudragit RS 100 polymer by a coacervation phase separation technique using variable proportions of polyisobutylene (0% to 3%) as a protective colloid. The micropellets were evaluated by scanning electron microscopy (SEM), particle size distribution, wall thickness, and loss of wall polymer were determined. The in vitro release experiments were carried out over the entire pH range of the gastrointestinal tract, the data obtained from the dissolution profiles were compared in the light of different kinetic models, and the regression coefficients were compared. The in vivo studies were performed on female human volunteers. A linear correlation was obtained from in vitro-in vivo studies.

Acrylic Resins↗
PubMed1994

Biopharmaceutical aspects of anti-infective therapy at the extremes of age.

Optimal anti-infective therapy at the extremes of age can be supported by the development of appropriate dosage forms. With regard to neonates, infants and children an oral liquid formulation appears to be superior compared with standard formulations such as tablets and capsules, since individualized dosing by body weight or body surface area is more easily achieved. Reformulation of marketed dosage forms, such as crunched tablets or opened capsules, by the hospital pharmacist may result in stability and bioavailability problems and therapeutic failures may be the consequence. With regard to the elderly a reduction in dosing frequency and individualized dosing are important in order to increase compliance. A reduction of dosing frequency can be achieved by oral controlled-release dosage forms, which are designed to release the drug in small amounts at predefined rates. However, to permit ease of swallowing they require a relative small daily dose together with excipients. In addition absorption must occur throughout the entire gastrointestinal tract; this is not the case for several antibiotics. Various advantages and disadvantages of oral liquid and oral controlled-release dosage forms are discussed. In the development of an oral formulation, in addition to a standard tablet a variety of information, such as physico-chemical characteristics, pharmacokinetics and pharmacodynamics must be available. Physico-chemical disadvantages can largely be solved by advanced pharmaceutical concepts, such as the pro-drug approach, complex formation or coprecipitation, which are discussed. Using ciprofloxacin with its long lasting and extremely bitter taste as an example, the pharmaceutical development of an oral liquid formulation and the pharmacokinetic investigations in healthy volunteers are described.

Administration, Oral↗
PubMed1978

Biopharmaceutical properties of liquid and tablet antacids: in vivo studies using the intragastric pH-measurement technique.

Three types of liquid and tablet antacids have been studied in vitro and in vivo: aluminium hydroxide, aluminium hydroxide-magnesium carbonate and hydrotalcite. The effects on gastric pH of antacid suspensions and antacid chewing tablets having identical active ingredients have been studied in 36 volunteers, the sequence of both forms of administration being randomized. Gastric acid secretion was continuously stimulated during the experiment by a pentagastrin infusion. Antacid chewing tablets gave inferior results when compared with the same antacid in liquid. Antacid suspensions are therefore preferred in the treatment of acid-peptic disease.

Antacids↗
PubMedDate not supplied

Molecular pathology in the preclinical development of biopharmaceuticals.

Advances in cell and molecular biology have engendered a wide range of techniques that can be used to study the molecular events that underlie the cause of disease, thus producing a new field of study called "molecular pathology." These techniques can be either slide-based or non-slide-based (solution-based). The slide-based techniques include immunohistochemistry, in situ hybridization, and in situ polymerase chain reaction; pathologists play a unique role in the administration of these techniques because of their ability to interpret the end product (i.e., the slide). In this manuscript, we briefly discussed the use and impact of these slide-based techniques within all phases of drug development in the pharmaceutical industry.

Animals↗