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PubMed1997

Biopharmaceutical aspects of lipid formulations of amphotericin B.

To improve the clinical utility of amphotericin B (AmpB), several lipid-based formulations have been developed. The biopharmaceutical aspects related to the parenteral use of colloidal lipid particles as carriers of AmpB are reviewed here. The first part of the review provides an introduction to the parenteral use of colloidal particles for chemotherapy by addressing the concept of a particulate drug carrier system, the pharmaceutical technological issues, and the biological factors governing the potential and limitations of lipid particles for effective drug delivery. The second part is devoted to AmpB lipid formulations. The pharmaceutical characteristics of the various industrially produced formulations, their pharmacokinetics and possible mechanisms of action, and potential future developments are described.

Amphotericin B↗
PubMed1989

Data-reduction problems in biopharmaceutics and pharmacokinetics.

The importance of the use of appropriate biostatistical methods is stressed. In this article some problems and common errors in the data-reduction methods applied in biopharmaceutical and pharmacokinetic research are discussed. A commonly used representation of a set of concentration-time curves is the so-called 'mean curve', a curve through the arithmetic means of concentrations at discrete time points. If individual curves are compared with the 'mean curve' it appears that important characteristics have disappeared while other, incorrect, characteristics have been created. Unreliable conclusions may result from this procedure. Rather every single concentration-time curve should be fitted by appropriate regression methods and the resulting parameters be considered as multiple characteristics of individual pharmacokinetic behaviour. In a second data-analysis step these parameters may be clustered into more or less homogeneous subgroups, which subsequently may be represented by a representative curve. Standard errors of the mean and confidence intervals based on standard errors of the mean instead of the standard deviation are often misused as dispersion measures to characterize the sample or population distribution. Standard errors of the mean and confidence intervals measure the precision of the mean of a sample and are sensitive to the sample size. Vertical bars (in curves) representing standard deviation, standard errors of the mean or confidence intervals suggest symmetrical distributions, but this is sometimes not justified. Deviations from normality appear to occur often. A simple graphical method to indicate the dispersion of non-normal sets is presented. Methods for the determination of confidence intervals for normal and non-normal distributions are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopharmaceutics↗
PubMed1994

Clinical implications of the biopharmaceutical properties of fluvastatin.

Fluvastatin sodium (Lescol; Sandoz) the first entirely synthetic 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor studied, is structurally distinct from the other HMG-CoA reductase inhibitors currently available, all of which are fungal metabolites and analogues of compactin. Fluvastatin's distinct structure may be responsible for the biopharmaceutical properties that result in its low systemic exposure and, subsequently, low incidence of peripheral adverse events, such as headache and myositis. Fluvastatin is rapidly absorbed from the gastrointestinal tract; has a 30-minute half-life, the shortest of any currently available HMG-CoA reductase inhibitor (lovastatin, 15 hours; pravastatin, 2 hours; simvastatin, 15.6 hours); is highly selective for the liver, undergoing extensive first-pass metabolism; has no active circulating metabolites; and does not penetrate the blood-brain barrier, unlike lovastatin and simvastatin. The low systemic exposure suggests that the occurrence of peripheral adverse events, such as myositis, central nervous system effects, and drug-drug interactions, may be less than what is currently observed with other HMG-CoA reductase inhibitors. Neither niacin nor propranolol had an effect on fluvastatin plasma levels when combined with fluvastatin. In contrast to other HMG-CoA reductase inhibitors, fluvastatin in combination with niacin resulted in no instances of myositis or other serious adverse events. Although the interaction of fluvastatin with cholestyramine resulted in a lower rate and extent of fluvastatin bioavailability, this reduction had no impact on clinical efficacy. Fluvastatin administered to patients chronically receiving digoxin had no effect on the area under the curve (AUC) of digoxin compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Advances in biopharmaceutical analysis in the People's Republic of China: 1991-1993.

The methodological studies on biopharmaceutical analysis of drugs and their metabolites by liquid and gas chromatography with various detectors have been reviewed. Research articles were selected from well known journals published in the People's Republic of China between January 1991 and March 1993. The applications of these methods in bioavailability, pharmacokinetics, therapeutic drug monitoring and metabolic studies have also been discussed.

Biopharmaceutics↗
PubMed2006

HTS technologies in biopharmaceutical discovery.

The concepts and philosophies of HTS can be productively applied to the discovery of new biopharmaceuticals. It is now possible, comprehensively and systematically, to enumerate, clone, produce and screen all secreted proteins, by building upon knowledge accumulated over the past two decades in HTS, genomics and parallel protein expression technologies. Each of the crucial operational components (comprehensive and high-quality cDNA library construction, proper protein-sequence classification, high-throughput protein production, medically relevant assays, state-of-the-art screening and data management) must be optimized to increase the chances of success. In this review, we draw comparisons between small-molecule and protein screening to illuminate common underlying principles as well as differences between the two operations.

Animals↗
PubMed2004

Classification of orally administered drugs on the World Health Organization Model list of Essential Medicines according to the biopharmaceutics classification system.

Since its inception in 1995, the biopharmaceutical classification system (BCS) has become an increasingly important tool for regulation of drug products world-wide. Until now, application of the BCS has been partially hindered by the lack of a freely available and accurate database summarising solubility and permeability characteristics of drug substances. In this report, orally administered drugs on the Model list of Essential Medicines of the World Health Organization (WHO) are assigned BCS classifications on the basis of data available in the public domain. Of the 130 orally administered drugs on the WHO list, 61 could be classified with certainty. Twenty-one (84%) of these belong to class I (highly soluble, highly permeable), 10 (17%) to class II (poorly soluble, highly permeable), 24 (39%) to class III (highly soluble, poorly permeable) and 6 (10%) to class IV (poorly soluble, poorly permeable). A further 28 drugs could be provisionally assigned, while for 41 drugs insufficient or conflicting data precluded assignment to a specific BCS class. A total of 32 class I drugs (either certain or provisional classification) were identified. These drugs can be further considered for biowaiver status (drug product approval based on dissolution tests rather than bioequivalence studies in humans).

Administration, Oral↗
PubMed2004

Solid-state characterization of rifampicin samples and its biopharmaceutic relevance.

Polymorphism of rifampicin has been postulated to be responsible for its variable bioavailability from solid oral dosage forms. In this regard, it was believed that form II is the preferred form and the content of amorphous needs to be critically monitored. However, there was no study in literature that determines solubility advantage associated with rifampicin polymorphs and further the desired raw material characteristics for the consistent bioavailability. Hence, this investigation was undertaken with an objective to determine biopharmaceutic relevance of rifampicin physical forms and to propose critical raw material specifications for rifampicin bulk material. For this purpose, solid-state properties of standard form I, form II, amorphous and commercial samples acquired from rifampicin manufacturers were characterized by differential scanning calorimetry (DSC), Fourier transformed infrared spectroscopy (FTIR), hot stage microscopy (HSM), thermogravimetric analysis (TGA), powder X-ray diffraction (p-XRD), solid-state nuclear magnetic resonance (NMR) and molecular modelling. In addition, intrinsic dissolution of standard samples, powder dissolution as well as particle size distribution of all the samples and powder dissolution of various sieve fraction of commercial samples were done in order to study the influence of polymorphism and other factors on rate and extent of dissolution. It was found that rifampicin in commercial bulk samples exist as various combinations of form I, form II and amorphous. As physical forms show comparable intrinsic dissolution rate (IDR) at all the pH values, solubility advantage associated with rifampicin polymorphs is negligible. Nevertheless, powder dissolution of commercial samples was influenced by particle size. In powder dissolution of different sieve fractions of commercial samples, fine particles below 100 microm have shown high rate and extent of dissolution irrespective of polymorphic content, whereas particles above 100 microm exhibited reduced dissolution. In intrinsic dissolution, thermodynamically unstable form II exhibited lower IDR than stable form I. Further, this difference is evident only at pH 2.0 and at all other pH values there was no difference in IDR of these two forms. For this unexpected finding, two hypotheses based on differences in H-bonding of the polymorph have been proposed.

Biological Availability↗
PubMed2006

A century of dissolution research: from Noyes and Whitney to the biopharmaceutics classification system.

Dissolution research started to develop about 100 years ago as a field of physical chemistry and since then important progress has been made. However, explicit interest in drug related dissolution has grown only since the realisation that dissolution is an important factor of drug bioavailability in the 1950s. This review attempts to account the most important developments in the field, from a historical point of view. It is structured in a chronological order, from the theoretical foundations of dissolution, developed in the first half of the 20th century, and the development of a relationship between dissolution and bioavailability in the 1950s, going to the more recent developments in the framework of the Biopharmaceutics Classification System (BCS). Research on relevant fields of pharmaceutical technology, like sustained release formulations, where drug dissolution plays an important role, is reviewed. The review concludes with the modern trends on drug dissolution research and their regulatory implications.

Animals↗
PubMed2005

Use of flow-cytometric analysis to optimize cell banking strategies for production of biopharmaceuticals from mammalian cells.

Production of biopharmaceuticals from mammalian cells requires generation of master, working and post-production cell banks of high quality under GMP conditions. An optimal cryopreservation strategy is needed for each new production cell line, particularly with regard to establishing production processes that are completely devoid of serum or even any animal components and to ensuring robust thaw performance for reliable production. Here, we describe a novel strategy employing flow-cytometric (FC) analysis of Annexin V-stained cells for high-throughput characterization of cell banks. Our data show that this method enables predictive evaluation of a cryopreservation strategy as early as 6h after thawing of cells. Furthermore, a broad study is presented characterizing various factors that may influence the quality of serum-free production cell banks from NSO and CHO cell lines. These results demonstrate how FC-based analysis can be used for development of future state-of-the-art cryopreservation strategies.

Animals↗
PubMed2005

Biopharmaceuticals: recent approvals and likely directions.

Some 160 biopharmaceuticals have now gained medical approval and several hundred are in the pipeline. Most are protein-based, although two nucleic acid-based products are now on the US/European market. An increasing proportion of approvals are engineered in some way and advances in alternative production systems and delivery methods will also likely impact upon the approvals profile over the remainder of this decade.

Biopharmaceutics↗
PubMed1998

The development of site-specific drug-delivery systems for protein and peptide biopharmaceuticals.

The desire to deliver protein and peptide biopharmaceuticals conveniently and effectively has led to intense investigation of site-specific drug-delivery systems. Despite challenges, progress towards the convenient noninvasive delivery of proteins and peptides has been achieved through specific routes of administration. In addition, the delivery of proteins and peptides to specific sites of action has been utilized to lower the total delivered dose, to gain access to specific organs or body compartments and to concentrate a therapeutic dose at a specific site of pharmacological action.

Biopharmaceutics↗
PubMed1997

A non-isotopic probe-hybridization assay for residual DNA in biopharmaceuticals.

Although most biopharmaceuticals are highly purified, there is a theoretical concern that such recombinant products could be contaminated with oncogenic or bacterial DNA. A crucial part of the control of such biologicals is to ensure they do not contain more residual DNA than a safety limit suggested by the regulatory agency. Currently, the FDA has suggested a 100 pg per dose limit for residual DNA. DNA probes labeled with a radioisotope such as 32P have been commonly used in hybridization tests. Because of the radiation safety concern, we chose to develop a procedure for assessing DNA levels by either a dot or slot blot hybridization technique using a nonisotopic DNA probe and immuno-enzymatic detection. A minimum detectable limit (MDL) of < 10 pg DNA mg(-1) protein can be achieved. Method validation data demonstrated that the precision, reproducibility, and robustness of this approach are appropriate for quality control.

Biopharmaceutics↗
PubMed2000

Biopharmaceutical formulation.

The rapid maturation of the field of biopharmaceutical formulation is the result of the simultaneous development of a thermodynamic mechanism for protein-solvent interaction and identification of natural chemicals employed by nature to stabilize proteins in response to environmental stresses. In general, these cosolvents are excluded from the protein surface. Proteins are maintained in their native folded conformations by these cosolvents as a result of the highly unfavorable interaction between cosolvents and peptide backbones, which would be exposed to the cosolvent upon unfolding.

Biopharmaceutics↗
PubMedDate not supplied

Mixing in process vessels used in biopharmaceutical manufacturing.

The use of nonbaffled vessels for mixing applications is becoming common in the biopharmaceutical industry but is not sufficiently well studied. Orientation of the impellers off-centered and/or at an angle is necessary to enhance mixing and eliminate swirling that would result without a baffle in a standard tank. This study focuses on characterizing mixing in vessels with the hydrofoil axial flow impellers mounted off-center at 10 degrees to the vertical. Geometrically similar vessels ranging from 100 to 5000 L working volume were used in this study. Mixing performance was successfully correlated to vessel geometric factors.

Biopharmaceutics↗
PubMed1999

Biopharmaceutics and pharmacokinetics of 5-phenyl-1, 2-dithiole-3-thione complexed with sulfobutyl ether-7-beta-cyclodextrin in rabbits.

The biopharmaceutics and pharmacokinetics of 5-phenyl-1, 2-dithiole-3-thione (5PDTT) were investigated in rabbits, after administration as a complex with sulfobutyl-ether-7-beta-cyclodextrin (SBE7-beta-CD) by intravenous and oral routes and as a micronized powder by oral route. 5PDTT had a rapid and large red blood cell partitioning that was not dependent on drug concentration either in vitro or ex vivo. The blood clearance was very high (354 +/- 131 mL/min) suggesting extrahepatic metabolism and/or nonrenal elimination and a significant volume of distribution (67 +/- 76 L). The renal clearance was 0.17% of total clearance. 5-phenyl-1,2-dithiol-3-one (5PDTO) was identified as a metabolite in blood and urine. The bioavailability of 5PDTT following administration of 5PDTT/SBE7-beta-CD complex was estimated to 41% while it was close to zero when 5PDTT was given as a micronized powder.

Administration, Oral↗
PubMedDate not supplied

A provisional biopharmaceutical classification of the top 200 oral drug products in the United States, Great Britain, Spain, and Japan.

Orally administered, immediate-release (IR) drug products in the top 200 drug product lists from the United States (US), Great Britain (GB), Spain (ES), and Japan (JP) were provisionally classified based on the Biopharmaceutics Classification System (BCS). The provisional classification is based on the aqueous solubility of the drugs reported in readily available reference literature and a correlation of human intestinal membrane permeability for a set of 29 reference drugs with their calculated partition coefficients. Oral IR drug products constituted more that 50% of the top 200 drug products on all four lists, and ranged from 102 to 113 in number. Drugs with dose numbers less than or equal to unity are defined as high-solubility drugs. More than 50% of the oral IR drug products on each list were determined to be high-solubility drugs (55-59%). The provisional classification of permeability is based on correlations of the human intestinal permeabilities of 29 reference drugs with the calculated Log P or CLogP lipophilicity values for the uncharged chemical form. The Log P and CLogP estimates were linearly correlated (r2 = 0.79) for 187 drugs. Metoprolol was chosen as the reference compound for permeability and Log P or CLogP. A total of 62-69.0% and 56-60% of the drugs on the four lists exhibited CLogP and Log P estimates, respectively, greater than or equal to the corresponding metoprolol value and are provisionally classified as high-permeability drugs. We have compared the BCS classification in this study with the recently proposed BDDCS classification based on fraction dose metabolism. Although the two approaches are based on different in vivo processes, fraction dose metabolized and fraction dose absorbed are highly correlated and, while depending on the choice of reference drug for permeability classification, e.g., metoprolol vs cimetidine or atenolol, show excellent agreement in drug classification. In summary, more than 55% of the drug products were classified as high-solubility (Class 1 and Class 3) drugs in the four lists, suggesting that in vivo bioequivalence (BE) may be assured with a less expensive and more easily implemented in vitro dissolution test.

Administration, Oral↗
PubMed1995

Lipid microemulsions for improving drug dissolution and oral absorption: physical and biopharmaceutical aspects.

PURPOSE: This review highlights the state-of-the-art in pharmaceutical microemulsions with emphasis on self-emulsifying systems, from both a physical and biopharmaceutical perspective. Although these systems have several pharmaceutical applications, this review is primarily focused on their potential for oral drug delivery and intestinal absorption improvement. METHODS: Physicochemical characteristics and formulation design based on drug solubility and membrane permeability are discussed. RESULTS: Case studies in which lipid microemulsions have successfully been used to improve drug solubilization/dissolution and/or intestinal absorption of poorly absorbed drugs/peptides are presented. CONCLUSIONS: Drug development issues such as commercial viability, mechanisms involved, range of applicability, safety, scale-up and manufacture are outlined, and future research and development efforts to address these issues are discussed.

Administration, Oral↗