Characterization of the oral absorption of several aminopenicillins: Determination of intrinsic membrane absorption parameters in the rat intestine in situ

The absorption mechanism of several penicillins was characterized using in situ single-pass intestinal perfusion in the rat. The intrinsic membrane absorption parameters were determined using a modified boundary layer model (fitted value +/- S.E.): J*max = 11.78 +/- 1.88 mM, Km = 15.80 +/- 2.92 mM, P*m = 0, J*c = 0.75 +/- 0.04 for ampicillin; J*max = 0.044 +/- 0.018 mM, Km = 0.058 +/- 0.026 mM, P*m = 0.558 +/- 0.051, P*c = 0.757 +/- 0.088 for amoxicillin; and J*max = 16.30 +/- 3.40 mM, Km = 14.00 +/- 3.30 mM, P*m = 0, P*c = 1.14 +/- 0.05 for cyclacillin. All of the aminopenicillins studied demonstrated saturable absorption kinetics as indicated by their concentration-dependent wall permeabilities. Inhibition studies were performed to confirm the existence of a nonpassive absorption mechanism. The intrinsic wall permeability (P*w) of 0.01 mM ampicillin was significantly lowered by 1 mM amoxicillin and the P*w of 0.01 mM amoxicillin was reduced by 2 mM cephradine consistent with competitive inhibition.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29839/1/0000186.pd

CHO/hPEPT1 cells overexpressing the human peptide transporter (hPEPT1) as an alternative in vitro model for peptidomimetic drugs

The present study characterized Chinese hamster ovary cells overexpressing a human intestinal peptide transporter, CHO/hPEPT1 cells, as an in vitro model for peptidomimetic drugs. The kinetic parameters of Gly-Sar uptake were determined in three different cell culture systems such as untransfected CHO cells (CHO–K1), transfected CHO cells (CHO/hPEPT1) and Caco-2 cells. V max in CHO/hPEPT1 cells was approximately 3-fold higher than those in Caco-2 cells and CHO–K1 cells, while K m values were similar in all cases. The uptake of β -lactam antibiotics in CHO/hPEPT1 cells was three to twelve fold higher than that in CHO–K1 cells, indicating that CHO/hPEPT1 cells significantly enhanced the peptide transport activity. However, amino acid drugs also exhibited high cellular uptake in both CHO–K1 and CHO/hPEPT1 cells due to the high background level of amino acid transporters. Thus, cellular uptake study in CHO/hPEPT1 cells is not sensitive enough to distinguish the peptidyl drugs from amino acid drugs. The potential of CHO/hPEPT1 cells as an in vitro model for peptidomimetic drugs was also examined through the inhibition study on Gly-Sar uptake. Peptidomimetic drugs such as β -lactam antibiotics and enalapril significantly inhibited Gly-Sar uptake whereas the nonpeptidyl compounds, l -dopa and α -methyldopa, did not compete with Gly-Sar for cellular uptake within the therapeutic concentrations. In conclusion, the present study demonstrates the further characterization of CHO/hPEPT1 cells as an uptake model as well as inhibition study and suggests their utility as an alternative in vitro model for drug candidates targeting the hPEPT1 transporter.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34496/1/11_ftp.pd

Absorption Rate Limit Considerations for Oral Phosphate Prodrugs

Purpose . To evaluate the potential of phosphate ester prodrugs to significantly improve the absorptive flux of poorly soluble parent drugs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41498/1/11095_2004_Article_465513.pd

Atrasentan and renal events in patients with type 2 diabetes and chronic kidney disease (SONAR): a double-blind, randomised, placebo-controlled trial

Background: Short-term treatment for people with type 2 diabetes using a low dose of the selective endothelin A receptor antagonist atrasentan reduces albuminuria without causing significant sodium retention. We report the long-term effects of treatment with atrasentan on major renal outcomes. Methods: We did this double-blind, randomised, placebo-controlled trial at 689 sites in 41 countries. We enrolled adults aged 18–85 years with type 2 diabetes, estimated glomerular filtration rate (eGFR)25–75 mL/min per 1·73 m 2 of body surface area, and a urine albumin-to-creatinine ratio (UACR)of 300–5000 mg/g who had received maximum labelled or tolerated renin–angiotensin system inhibition for at least 4 weeks. Participants were given atrasentan 0·75 mg orally daily during an enrichment period before random group assignment. Those with a UACR decrease of at least 30% with no substantial fluid retention during the enrichment period (responders)were included in the double-blind treatment period. Responders were randomly assigned to receive either atrasentan 0·75 mg orally daily or placebo. All patients and investigators were masked to treatment assignment. The primary endpoint was a composite of doubling of serum creatinine (sustained for ≥30 days)or end-stage kidney disease (eGFR <15 mL/min per 1·73 m 2 sustained for ≥90 days, chronic dialysis for ≥90 days, kidney transplantation, or death from kidney failure)in the intention-to-treat population of all responders. Safety was assessed in all patients who received at least one dose of their assigned study treatment. The study is registered with ClinicalTrials.gov, number NCT01858532. Findings: Between May 17, 2013, and July 13, 2017, 11 087 patients were screened; 5117 entered the enrichment period, and 4711 completed the enrichment period. Of these, 2648 patients were responders and were randomly assigned to the atrasentan group (n=1325)or placebo group (n=1323). Median follow-up was 2·2 years (IQR 1·4–2·9). 79 (6·0%)of 1325 patients in the atrasentan group and 105 (7·9%)of 1323 in the placebo group had a primary composite renal endpoint event (hazard ratio [HR]0·65 [95% CI 0·49–0·88]; p=0·0047). Fluid retention and anaemia adverse events, which have been previously attributed to endothelin receptor antagonists, were more frequent in the atrasentan group than in the placebo group. Hospital admission for heart failure occurred in 47 (3·5%)of 1325 patients in the atrasentan group and 34 (2·6%)of 1323 patients in the placebo group (HR 1·33 [95% CI 0·85–2·07]; p=0·208). 58 (4·4%)patients in the atrasentan group and 52 (3·9%)in the placebo group died (HR 1·09 [95% CI 0·75–1·59]; p=0·65). Interpretation: Atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease who were selected to optimise efficacy and safety. These data support a potential role for selective endothelin receptor antagonists in protecting renal function in patients with type 2 diabetes at high risk of developing end-stage kidney disease. Funding: AbbVie

Estimating oral drug absorption in humans.

A physical absorption model has been developed using a microscopic mass balance. This model can be used to estimate the extent and rate of oral absorption for compounds absorbed by carrier-mediated as well as passive absorption mechanisms. Using wall permeability parameters of aminopenicillins measured in rats, competitive drug-drug interactions during oral absorption were estimated with regard to the fraction dose absorbed (F) and absorption rate constant. Wall permeabilities of several $\beta$-lactam antibiotics were determined by single-pass perfusion experiments in rats. Ampicillin, amoxicillin, cyclacillin, and cefixime were shown to be absorbed by a carrier-mediated absorption mechanism, from results that showed concentration-dependent permeabilities and competitive inhibition. Our results have suggested that an $\alpha$-amino group on the side chain may be sufficient but not necessary for the absorption of $\beta$-lactam antibiotics via the peptide transporter. The fraction dose absorbed of suspensions of poorly soluble drugs was estimated using a microscopic mass balance approach. There are four underlying dimensionless parameters controlling F: absorption number (An), dose number (Do), dissolution number (Dn), and initial saturation (Is). Is is the drug concentration at the beginning of the intestine. An is the ratio of radial absorption rate to axial convection rate. Do is the ratio of dose concentration to solubility of a drug. Dn is the ratio of residence time in the intestine to dissolution time from particles. Solubility at the physiological pH should be used for calculating Do and Dn of weakly acidic or basic drugs. It was found that F increases with increasing Is, An and Dn, and with decreasing Do. F can be limited by An, Do, or Dn. These parameters should be considered when investigating the bioavailability of a new drug. The effect of micronization on F from suspensions was investigated in terms of Dn. About 90% of maximal F may be achieved at Dn $\approx$ 2. Complete drug absorption can be achieved for drugs with low Do and low Dn by reducing the particle size, whereas drugs with high Do and low Dn may also require a higher solubility to enhance F.Ph.D.PharmaceuticsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/105417/1/9124068.pdfDescription of 9124068.pdf : Restricted to UM users only

Effect of micronization on the extent of drug absorption from suspensions in humans

A microscopic mass balance approach has shown that the initial saturation (Is), absorption number (An), dose number (Do), and dissolution number (Dn) are four fundamental dimensionless parameters that can be used to estimate the fraction dose absorbed (~ of suspensions of poorly soluble drugs in humans. The dissolution number of a drug increases with decreasing its particle size. The effect of micronization on F for suspensions was investigated in terms of Dn. About 90% of maximal Fcan be achieved at Dn-~2. Increasing the solubility of a drug results in better oral absorption through increasing Dn and decreasing Do. The fractions dose absorbed of digoxin, griseofulvin, and benoxaprofen agree with predicted F values using estimated parameters. Drugs with low Do and low Dn can be more completely absorbed by reducing particle size, while absorption of drugs with high Do and low Dn is limited by solubility and requires higher solubility to enhance the fraction dose absorbed in addition to micronization. Solubility at the physiological pH should be used for the estimation of the fraction dose absorbed.NIGMS Grant GM 37188.http://deepblue.lib.umich.edu/bitstream/2027.42/122837/1/Oh(1995)Micronization.pdfDescription of Oh(1995)Micronization.pdf : Main articl

Cellular Uptake Mechanism of Amino Acid Ester Prodrugs in Caco-2/hPEPT1 Cells Overexpressing a Human Peptide Transporter

Purpose . This study characterized the cellular uptake mechanism and hydrolysis of the amino acid ester prodrugs of nucleoside antiviral drugs in the transiently transfected Caco-2 cells overexpressing a human intestinal peptide transporter, hPEPTl (Caco-2/hPEPTl cells).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41471/1/11095_2004_Article_303990.pd

Estimating the Fraction Dose Absorbed from Suspensions of Poorly Soluble Compounds in Humans: A Mathematical Model

A microscopic mass balance approach has been developed to predict the fraction dose absorbed of suspensions of poorly soluble compounds. The mathematical model includes four fundamental di-mensionless parameters to estimate the fraction dose absorbed: initial saturation ( Is ), absorption number ( An ), dose number ( Do ), and dissolution number ( Dn ). The fraction dose absorbed ( F ) increases with increasing Is , An , and Dn and with decreasing Do . At higher Dn and lower Do , the fraction dose absorbed reaches the maximal F , which depends only on An . The dissolution number limit on F can appear at both lower Do and lower Dn . Likewise, at higher Do and Dn , the fraction dose absorbed reaches a Do limit. Initial saturation makes a significant difference in F at lower Do and Dn . It is shown that the extent of drug absorption is expected to be highly variable when Dn and Do are approximately one. Furthermore, by calculating these dimensionless groups for a given compound, a formulation scientist can estimate not only the extent of drug absorption but also the effect, if any, of particle size reduction on the extent of drug absorption.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41428/1/11095_2004_Article_304768.pd

Fabrication of CP-Ti structure with controllable wettability using powder bed fusion and eco-friendly post-process

Abstract Hydrophobic surfaces have a wide range of applications, such as water harvesting, self-cleaning, and anti-biofouling. However, traditional methods of achieving hydrophobicity often involve the use of toxic materials such as fluoropolymers. This study aims to create controllable wettability surfaces with a three-dimensional geometry using a laser base powder bed fusion (PBF) process with commercially pure titanium (CP-Ti) and silicone oil as non-toxic materials. The optimal PBF process parameters for fabricating micropillar structures, which are critical for obtaining the surface roughness necessary for achieving hydrophobic properties, were investigated experimentally. After fabricating the micropillar structures using PBF, their surface energy was reduced by treatment with silicone oil. Silicone oil provides a low-surface-energy coating that contributes to the water-repellent nature of hydrophobic surfaces. The wettability of the treated CP-Ti surfaces was evaluated based on the diameter of the pillars and the space between them. The structure with the optimal diameter and spacing of micropillars exhibited a high contact angle (156.15°). A pronounced petal effect (sliding angle of 25.9°) was achieved because of the morphology of the pillars, indicating the controllability of wetting. The micropillar diameter, spacing, and silicone oil played crucial roles in determining the water contact and sliding angle, which are key metrics for surface wettability