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Biomedical subjects

M Shameem

Publications and source records attributed to M Shameem.

10 recordsLinked to original sources
PubMed2005

Camptomelic dysplasia with sex reversal.

Camptomelic dysplasia is a disorder of the newborn characterized by congenital bowing and angulation of long bones together with other skeletal and extraskeletal defects. The affected newborn had dysmorphic features with bowing of the legs and bilateral talipes equinovarus. Radiology showed marked anterior bowing of both tibia with disproportionately short fibula, anterolateral bowing of the femurs and wide pelvic outlet with small iliac wings. She had sex reversal with normal female genitalia and 46, XY karyotype. Camptomelic dysplasia is generally considered to be a lethal skeletal dysplasia and most patients die in the neonatal period due to severe respiratory distress. Survivors may have learning difficulties, developmental delay, conductive hearing loss, myopia and recurrent chest infections. Because of its high associated mortality, prenatal diagnosis of camptomelic dysplasia is mandatory. The birth of a child with skeletal dysplasia is an emotionally difficult experience for parents.

Abnormalities, Multiple↗
PubMed2000

Extended release peptide delivery systems through the use of PLGA microsphere combinations.

The purpose of this study was to evaluate the utility of combining polymer matrices to overcome extended lag periods or unacceptably short durations of action intrinsic in the individual polymer systems. Leuprolide, an LHRH superagonist, was incorporated into a variety of poly(lactide-co-glycolide) (PLGA) matrices using a solvent extraction/evaporation method. The in vitro release of Leuprolide from these matrices was evaluated at pH 7.0 and 37 degrees C in phosphate buffer. The formulations were administered to an animal model at 3 or 9 mg kg(-1) doses and serum testosterone levels were followed using a RIA method. A two-part system was made by combining microspheres made from a 75:25 acid terminated PLGA and microspheres made from a 75:25 ester terminated PLGA. This combination elicited chemical castration from 10-100 days. A three-part combination composed of an ester terminated 75:25 PLGA formulation, an ester terminated 50:50 PLGA formulation and an acid terminated 50:50 PLGA formulation also provided a composite profile with an onset of 10 days and a duration of approximately 100 days. Additionally, a single polymer system composed of a high molecular weight ester terminated 75:25 PLGA was employed to produce release over the desired 90-day release period. This study demonstrates that microsphere combinations can potentially provide effective therapies over extended intervals when combined at the proper ratio.

Animals↗
PubMed1999

A short term (accelerated release) approach to evaluate peptide release from PLGA depot-formulations.

An accelerated method to evaluate peptide release from poly(dl-lactide-co-glycolide) (PLGA) depot formulations in short time is described. Peptide-loaded microspheres were made from hydrophilic 50:50 PLGA by a dispersion-solvent extraction technique, and peptide release was studied at 37 degrees C and at higher temperatures in various media. For all accelerated conditions, release was faster at temperatures above the glass transition, Tg, of the host polymer. Complete release of peptide from 8600 MW PLGA was achieved in 35 hours at 50 degrees C in buffered and nonbuffered media containing 0.5% polyvinyl alcohol (PVA). Type of release media and concentration of PVA influenced the release profiles. A PVA concentration of 0.1 to 0.5% was found to prevent aggregation of microspheres at higher temperatures, with an increase in release at the higher PVA concentration. Peptide release was associated with a reduction of pH of the releasing media and increased mass loss. Complete peptide release at pH 4 from 8.6 kd and 28 kd PLGA at 50 and 60 degrees C occurred within 30-40 hours and correlated well with the real-time release at 37 degrees C and pH 7.0. At the higher molecular weight, a slightly longer accelerated release time and higher temperature were required to correlate with the real-time release. The data suggest that by optimization of release conditions such as temperature, surfactant concentration, buffer component, and pH, an accelerated study could be employed to evaluate depot formulations for a given polymer type.

Buffers↗
PubMed1998

Casein hydrolysate as a rapid and/or enteric dissolving additive for oral drugs.

Two types of casein hydrolysates, casein A (mean peptide length 3.3) and casein B (mean peptide length 17.4) were prepared by the enzymatic hydrolysis of casein, and their effects on in vitro dissolution rates and oral bioavailability of drugs were evaluated. The in vitro dissolution behavior of the kneaded mixture of three drugs (diclofenac acid, diazepam, and prednisolone) with caseins A and B were significantly improved compared to the drugs alone, even at 1:1 weight ratio of drug and casein hydrolysate, even though casein A and casein B did not interact with drug molecules in the kneaded mixture. Only diclofenac, an acidic drug, showed an increased dissolution rate with added casein hydrolysates, and a more rapid dissolution with casein A than with casein B was observed. When the dissolution of prednisolone from kneaded mixture was compared at pH 1.2 and 6.8, the dissolution rate of prednisolone from the casein A kneaded mixture was considerably higher than that of prednisolone powder at both pHs, and the rate from the casein B kneaded mixture was higher only at pH 6.8. The plasma concentration-time profile showed that prednisolone was completely and rapidly absorbed from the casein A kneaded mixture as well as the prednisolone solution. In addition, prednisolone in the kneaded mixture with casein B was more difficult to absorb up to 1 hr after administration in comparison to prednisolone powder. The slow and lowered absorption of prednisolone by casein B might be explained by conversion of casein B to a shorter soluble peptide in the gastrointestinal tract and by the slow dissolution of prednisolone at acidic conditions. The toxicological tests revealed that casein hydrolysate is a safe drug carrier. Consequently, casein hydrolysates might be safely used to control the dissolution rate and bioavailability of a variety of drugs, depending on the peptide length of the casein fragments.

Animals↗
PubMed1995

Oral solid controlled release dosage forms: role of GI-mechanical destructive forces and colonic release in drug absorption under fasted and fed conditions in humans.

PURPOSE: This study was undertaken to examine the effects of mechanical destructive forces on drug release from controlled release (CR) dosage forms in vitro and in vivo and their colonic release, using two CR tablets of acetaminophen A and B, showing slower and faster erosion rates, respectively. METHODS: In vitro release rates were determined by several official methods. Tablets were administered to healthy volunteers under fasting and fed conditions. RESULTS: Both tablets showed similar release rates under mild destructive conditions (e.g., paddle method at 10 rpm) but CR-B showed faster release under highly destructive conditions (e.g., rotating basket method at 150 rpm), where the tablet was eroded. The in vivo release from CR-B was faster than from CR-A, possibly because of enhanced erosion. The variable in vivo release from CR-B indicated large inter-subject differences in destructive GI forces. The fastest in vivo release from CR-B among individuals was approximated by the in vitro dissolution determined by destructive methods such as the rotating basket at 150 rpm. The slowest in vivo release from tablets A and B was lower than the dissolution by the paddle method at 10 rpm. The release from both tablets was markedly reduced at 3-4 hrs after dosing irrespective of feeding conditions which can be attributed to release inhibition in the colon. CONCLUSIONS: Effects of GI destructive forces on the tablet erosion and the release inhibition in the colon must be considered in the development of CR dosage forms.

Acetaminophen↗
PubMed1994

Stereoselective hydrolysis of O-isovaleryl propranolol and its influence on the clearance of propranolol after oral administration.

The stereoselective hydrolysis of O-isovaleryl propranolol (isovaleryl-PL) was studied using phosphate and Tris-HCl buffers (pH 7.4), dog plasma, and liver preparations. The 10000g supernatant, microsomes, and cytosol were prepared from the liver homogenate. The hydrolysis rate of isovaleryl-PL was accelerated in the order Tris buffer < plasma = phosphate buffer << 10000g supernatant of liver = liver cytosol < liver microsomes. The high plasma protein binding of the prodrug brought about the extremely slow hydrolysis rate of isovaleryl-PL in plasma. No difference was observed in the hydrolysis rate between the isomers of isovaleryl-PL in buffers. The hydrolysis rate was 2-3 times faster with the (R)-isomer than with the (S)-isomer using racemate in dog plasma and liver preparations. The hydrolysis of each enantiomer was inhibited by the other enantiomer. For hydrolysis in microsomes the Km values of (R)- and (S)-isomers were same, and the Vmax of the (R)-isomer was 3 times greater than that of the (S)-isomer. These data suggested the mutual interaction of (R)- and (S)-isomers during the hydrolysis process and the rapid hydrolysis of isovaleryl-PL in liver after absorption. The AUC of PL enantiomers after oral administration of racemic isovaleryl-PL was about 2 times higher compared to 2 mg/kg equivalent molar dose of racemic PL in beagle dogs, and the corresponding plasma levels were not stereoselective from both PL and prodrug. The amount of (R)-PL absorbed after administration of a 5 mg/kg dose of racemic PL was 2-fold greater than (S)-PL, because of the stereoselective oxidation and glucronidation of (S)-PL.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

An in-vitro and in-vivo correlative approach to the evaluation of ester prodrugs to improve oral delivery of propranolol.

A series of ester prodrugs of propranolol was synthesized by incorporating substituents (straight alkyl, branched alkyl, acyloxyalkyl and cycloalkyl) into the beta-hydroxy function of propranolol with the aim of protecting the drug against first-pass metabolism following oral administration. The in-vitro hydrolysis rates of the prodrugs were, in increasing order, liver homogenate >> plasma > buffers. The pH-rate profile of the prodrugs showed maximum stability around pH 4.0; the hydrolysis rates were drastically increased over pH 6.8. QSAR analysis revealed hydrophobic (pi) and electronic (sigma) effects of the substituents play the main roles for prodrug hydrolysis in buffers and plasma, while hydrolysis in liver homogenate could not be well explained by any of these parameters. Four prodrugs (O-acetyl-, O-butyryl-, O-isovaleryl- and O-cyclopropanoyl-propranolol) were selected for oral administration based on their hydrolysis in-vitro. Following oral administration of prodrugs to beagle dogs the absolute bioavailabilities (F) of propranolol were about 2-4-fold that after an equivalent dose of propranolol. The prodrugs were rapidly absorbed and regenerated propranolol to attain peak plasma levels at 0-0.5h. Intact prodrug levels were also observed, which varied depending on their respective stabilities in in-vitro media. A linear relationship between F of propranolol and log P was obtained. F further appeared to be parabolically dependent on the observed hydrolysis rates of prodrugs in liver homogenate suggesting optimal design manipulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1992

Enantioselective oral bioavailability of 0-isovaleryl propranolol as a potential prodrug of propranolol.

The enantioselective oral bioavailability of propranolol (PL) from 0-isovaleryl-PL was determined and compared with parent PL in beagle dogs. The bioavailability of the individual enantiomer from the prodrug increased about 2 fold. The AUC ratio between the S(-)- and R(+)-isomer posed at 0.89 which was statistically not different from that obtained after administration of PL alone. These features indicate that 0-isovaleryl-PL promises to be a potential prodrug of PL from the pharmacokinetic and pharmacodynamic point of view.

Administration, Oral↗
PubMedDate not supplied

Effect of gamma-irradiation on peptide-containing hydrophilic poly (d,l-lactide-co-glycolide) microspheres.

The effect of gamma-irradiation on the physicochemical properties of peptide-containing hydrophilic poly (d,l-lactide-co-glycolide) (PLGA) microspheres was evaluated. PLGA (50/50, Mw: 8,600) with free carboxylic end groups was used to make drug-loaded and placebo microspheres by a solvent extraction evaporation method. Both formulated and non-formulated microspheres were gamma-irradiated at 0, 1, 1.5, and 2.5 Mrad doses. HPLC analysis based on extraction of peptide from the microspheres showed that peptide content of the microspheres was lowered upon irradiation and the reduction was more pronounced in formulated microspheres. The in-vitro release in 0.033M phosphate buffer, pH 7.0 at 37 degrees C (based on extraction of residual peptide) showed that the initial and subsequent release of peptide was higher in gamma-irradiated microspheres during the first 20 days. The difference became insignificant during the erosional controlled release of the peptide. There was no difference in release between the formulated and non-formulated microspheres of the nonirradiated or irradiated forms. Molecular weights (Mw and Mn), determined by size exclusion chromatography, were reduced by gamma-irradiation for both formulated and non-formulated placebo microspheres. Differential scanning calorimetry showed a gradual reduction in Tg of placebo microspheres but no reduction in peptide-loaded microspheres. In-vivo evaluation of the nonirradiated and the 1.5 Mrad irradiated microspheres showed no marked differences through 28 days. Since irradiation caused a lowering of Mw and Mn with the appearance of a low amount of unidentified substances, seemingly catalyzed by the polymer and the formulation excipients, gamma-irradiation sterilization of these parenteral delivery systems requires careful investigation on an individual product basis.

Gamma Rays↗