A systematic review and meta-analysis of the safety and efficacy of fistula laser closure

BACKGROUND

Fistula laser closure (FiLaC) is a novel sphincter-saving technique for the treatment of fistula-in-ano. The aim of this study was to assess the safety and efficacy of the FiLaC procedure.

METHODS

Databases including PubMed/Medline, Scopus, Web of Science, and Embase were searched for articles assessing FiLaC. All studies including case series and comparative studies reporting the outcome of FiLaC in the treatment of fistula-in-ano were considered eligible. The main outcomes were healing rates of fistula laser closure, postoperative complications including incontinence, technical aspects of the procedure and failure of healing.

RESULTS

Seven studies were included. There were a total of 454 patients, 69.1% with a transsphincteric fistula-in-ano and 35% with recurrent disease. The median age of the patients was 43 years (range 18-83 years). The median operation time was 18.3 min (range 6-32 min). With a median follow-up of 23.7 months, the weighed mean rate of primary healing was 67.3% and the overall success when FiLaC was reused was 69.7%. The weighted mean rate of complications was 4%, all of them were minor complications and the weighted mean rate of continence affection was 1% in the form of minor soiling.

CONCLUSIONS

FiLaC may be considered an effective and safe sphincter-saving technique for the treatment of fistula-in-ano with an acceptable, low, complication rate. However, well-designed randomized control trials comparing FiLaC with other techniques are required to substantiate the promising outcomes reported in this review.

Systematic review of endoluminal vacuum-assisted therapy as salvage treatment for rectal anastomotic leakage

Background

Endoluminal vacuum-assisted therapy (EVT) has been introduced recently to treat colorectal anastomotic leakage. The aim of this study was to evaluate the safety and efficacy of EVT in the treatment of anastomotic leakage and rectal stump insufficiency after Hartmann's procedure.

Methods

A systematic search of MEDLINE, Scopus and Cochrane databases was performed using search terms related to EVT and anastomotic leakage or rectal stump insufficiency in line with the PRISMA checklist. Observational studies, RCTs and case series studies published to July 2017 were included. Primary outcomes of the review were the success of EVT, defined as complete or partial healing of the anastomotic defect and associated cavity, and the rate of stoma reversal after EVT. Secondary outcomes included the duration of treatment to complete healing, complications of treatment and the need for further intervention. A meta-analysis was conducted. The potential effect of clinical confounders on the failure of EVT was investigated using the random-effects meta-regression model.

Results

Of 476 articles identified, 17 studies reporting on 276 patients were ultimately included. The weighted mean rate of success was 85·3 (95 per cent c.i. 80·1 to 90·5) per cent, with a median duration from inception of EVT to complete healing of 47 (range 40-105) days. The weighted mean rate of stoma reversal across the studies was 75·9 (64·6 to 87·2) per cent. Twenty-five patients (9·1 per cent) required additional interventions after EVT. Thirty-eight patients (13·8 per cent) developed complications. The weighted mean complication rate across the studies was 11·1 (6·0 to 16·2) per cent. Variables significantly associated with failure included preoperative radiotherapy, absence of diverting stoma, complications and male sex.

Conclusion

EVT is associated with a high rate of complete healing of anastomotic leakage and stoma reversal. It is an effective option in appropriately selected patients with anastomotic leakage.

Management of acute uncomplicated diverticulitis without antibiotics: a systematic review, meta-analysis, and meta-regression of predictors of treatment failure

BACKGROUND

Diverticulitis is a common complication of diverticular disease of the colon. While complicated diverticulitis often warrants intervention, acute uncomplicated diverticulitis (AUD) is usually managed conservatively. The aim of the present review was to evaluate the efficacy and safety of conservative treatment of AUD without antibiotics compared to standard antibiotic treatment.

METHODS

A systematic literature review in compliance with PRISMA guidelines was conducted. Electronic databases including PubMed/Medline, Scopus, Embase and Cochrane central register of controlled trials were searched. Studies that assessed efficacy and safety of treatment of AUD without antibiotics were included. Outcome parameters were rates of treatment failure, recurrence of diverticulitis, complications and mortality, readmission to hospital, and need for surgery.

RESULTS

Nine studies including 2565 patients were included to the review. Of these patients, 65.1% were treated conservatively without antibiotics. Treatment failure was observed in 5.1% of patients not-given-antibiotic treatment versus 3.4% of those given antibiotic treatment. Recurrent diverticulitis occurred in 9.3% of patients in the non-antibiotic group versus 12.1% of patients in the antibiotic group. On meta-analysis of the studies, there were no significant differences between non-antibiotic and antibiotic treatment groups regarding rates of treatment failure (OR = 1.5, p = 0.06), recurrence of diverticulitis (OR = 0.81, p = 0.2), complications (OR = 0.56, p = 0.25), readmission rates (OR = 0.97, p = 0.91), need for surgery (OR = 0.59, p = 0.28), and mortality (OR = 0.64, p = 0.47). The only variable that was significantly associated with treatment failure in the non-antibiotic treatment group was associated comorbidities (standard error (SE) = - 0.07, 95% CI - 0.117 - 0.032; p < 0.001).

CONCLUSIONS

Treatment of AUD without antibiotics is feasible, safe, and effective. Adding broad-spectrum antibiotics to the treatment regimen did not serve to decrease treatment failure, recurrence, complications, hospital readmissions, and need for surgery significantly compared to non-antibiotic treatment.

91-Year-Old Allograft: Oldest Surviving Donor Heart Still Going: A Case Report

For patients with end-stage heart failure, heart transplantation remains one of the most successful therapies with excellent long-term survival rates. However, over the past few decades, there has been a worsening supply/demand mismatch given the rising epidemic of heart failure and the relatively fixed availability of donor hearts. In this case report, we describe the case of a 30-year-old woman who underwent transplantation with a 68-year-old donor heart and who has survived for 23 years without any major cardiac problems. To our knowledge, this patient has one of the oldest surviving donor hearts (91-year-old heart). Review of the latest guidelines and recent studies have demonstrated a gradual expansion of donor criteria to meet this critical shortage of donor organs.

Poly(dimethylsiloxane) coatings for controlled drug release--polymer modifications

Modifications of endhydroxylated poly(dimethylsiloxane) (PDMS) formulations were studied for their ability to be applied onto tablet cores in a spray-coating process and to control drug release in zero-order fashion. Modifications of the crosslinker from the most commonly used tetraethylorthosilicate (TEOS) to the trifunctional 3-(2,3-epoxypropoxy)propyltrimethoxysilane (SIG) and a 1:1 mixture of the two were undertaken. Addition of methylpolysiloxane-copolymers were studied. Lactose, microcrystalline cellulose (MCC) and polyethylene glycol 8000 (PEG) were the channeling agents applied. The effects on dispersion properties were characterized by particle size distribution and viscosity. Mechanical properties of resulting free films were studied to determine applicability in a pan-coating process. Release of hydrochlorothiazide (marker drug) was studied from tablets coated in a lab-size conventional coating pan. All dispersions were found suitable for a spray-coating process. Preparation of free films showed that copolymer addition was not possible due to great decline in mechanical properties. Tablets coated with formulations containing PEG were most suitable to control drug release, at only 5% coating weight. Constant release rates could be achieved for formulations with up to 25% PEG; higher amounts resulted in a non-linear release pattern. Upon adding 50% PEG, a drug release of 63% over 24 h could be achieved.

Influence of methacrylic acid and hydroxypropylmethyl cellulose on the tablet properties and in vitro release of dextromethorphan hydrobromide

The release of dextromethorphan hydrobromide from matrices containing hydroxypropylmethyl cellulose (HPMC K100LV) and methacrylic acid copolymer (Eudragit L100-55) has been evaluated at different ratios of the polymers. The physicochemical properties (including weight, thickness, crushing strengh, friability and disintegration time) were also determined at 1000, 2000 and 4000 p compression forces. No significant differences in weight uniformity and thickness values were observed between the different formulations. The crushing strength of the tablets increased with increasing compression force and it reached a constant level at 4000 p. The formulations containing only HPMC K100LV resulted in an extended release pattern, however, Eudragit L100-55 alone could not effectively prolong the drug release. A combination of HPMC K100LV and Eudragit L100-55 in a 1:1 ratio at the 40% level provided an almost similar drug release profile than the marketed product.

Effect of drug proportion and mixing time on the content uniformity of a low dose drug in a high shear mixer

The purpose of this study was to investigate the effect of reducing drug proportion and mixing time on the content uniformity of a low dose drug. Buspirone hydrochloride was used as a model drug and was mixed with other ingredients in two different concentrations (0.5% w/w and 5% w/w) in a T. K. Fielder high shear mixer at a high impeller speed (522 rpm) and a high chopper speed (3600 rpm) up to 32 min. Samples were withdrawn from nine locations in the mixer at specific time points using a side-sampling thief probe. The final blends at 32 min were compressed using an instrumented tablet press. Tablets were sampled at the beginning, middle, and end of the compression run. The statistical results indicated that the drug proportion had a significant effect on the content uniformity of the powder blend and the corresponding tablets. For this study, the optimum time to mix the 0.5% w/w formulation was after 8 min while it was only 1 min for the 5% w/w formulation. The RSD of buspirone hydrochloride contents of tablets decreased as the compression run was toward its end. Uniformly mixed blends produced tablets that met the USP XXIV content uniformity requirements.

A comparative multidose pharmacokinetic study of buspirone extended-release tablets with a reference immediate-release product

Buspirone is disclosed in U.S. Patent No. 3,717,634 as a pharmaceutically active compound that has been found to be effective for the treatment of anxiety disorders and depression. In this randomized, two-treatment, two-period, multidose crossover study, the pharmacokinetics of a once-daily extended-release (ER)formulation of buspirone was compared with that of an immediate-release (IR) formulation of commercially available buspirone. A total of 30 mg of the ER formulation was administered to 36 healthy volunteers once daily for 7 days, and 15 mg of the IR formulation was administered twice daily for 7 days. Pharmacokinetic profiles of buspirone and its metabolite, 1-pyrimidinylpiperazine (1-PP), were obtained at steady state. The bioavailability of buspirone from the ER formulation was more than three times higher than that from the IR formulation at steady state, and that of 1-PP was about 25% less. The mean steady-state Cmax of buspirone from the ER formulation was 46% higher than that from the IR formulation (p < 0.05), and that for 1-PP was lower by 29% (p < 0.05). The mean apparent half-life of buspirone from the ER formulation (9.04 hours) was considerably longer than that observed for the IR formulation (3.06 hours). The median 1-PP/buspirone AUC ratio was much higher for the IR formulation at steady state (24.4) than for the ER formulation (6.44). There were no significant differences in average pharmacokinetic metrics observed in men and women. Based on these observations of the potential benefits of once-daily dosing with the ER product in terms of prolonged buspirone plasma concentrations, a significant increase in the ratio of buspirone to 1-PP concentration with a lower intersubject variation could be achieved that should provide an improvement in the desired therapeutic effects of buspirone.

Effect of anionic polymers on the release of propranolol hydrochloride from matrix tablets

Anionic polymers, namely Eudragit S, Eudragit L 100-55, and sodium carboxymethylcellulose, were incorporated into hydroxypropylmethylcellulose (HPMC K100M) to modify the drug release from HPMC matrices. The effects of changing the ratio of HPMC to anionic polymers were examined in water and in media with different pH. The dissolution profiles were compared according to release rates. The interaction between propranolol hydrochloride and anionic polymers was confirmed using the UV difference spectra method. The drug release was controlled with the type of anionic polymer and the interaction between propranolol hydrochloride and anionic polymers. The HPMC-anionic polymer ratio also influenced the drug release. The matrix containing HPMC-Eudragit L 100-55 (1:1 ratio) produced pH-independent extended-release tablets in water, 0.1 N HCl, and pH 6.8 phosphate buffer.

Pharmacokinetics of buspirone extended-release tablets: a single-dose study

The objective of this study is to evaluate the absorption of buspirone and its biotransformation to 1-(2-pyrimidinyl) piperazine (1-PP) from two different extended-release (ER) formulations of buspirone HCl tablets (12-hour and 24-hour in vitro release) and from a commercially available immediate-release (IR) tablet. A single dose of the 30 mg ER tablets was compared with two doses of the 15 mg IR tablet administered 12 hours apart. Eighteen healthy male subjects participated in this randomized, open-label, three-treatment crossover study. Blood samples were obtained at 22 time points from predose (0 hour) until 36 hours postdose, and plasma concentration of buspirone and 1-PP was determined by LC/tandem mass spectrometry method. The pharmacokinetic parameters AUC0-t, AUC0-infinity, Cmax, tmax, Ke, and t1/2 were calculated and statistically analyzed. The results indicated extended release of buspirone from the two test products in vivo with a 70% to 90% greater bioavailability in comparison with the IR formulation. The bioavailability of 1-PP from ER formulations appears to be equal to that from the IR formulation. Both buspirone ER tablets successfully delivered bioavailable buspirone with a reduction in peak drug and metabolite plasma levels, prolonged buspirone plasma concentrations, and decreased ratio of 1-PP to buspirone concentration with less intersubject variation when evaluated as a single-dose study in healthy human subjects.

The effects of packaging on the stability of a moisture sensitive compound

Packages that provided stability (less than a 10% loss in potency) of a moisture sensitive compound (PGE-7762928) in tablet form at accelerated conditions for 6 months were identified. The equilibrium moisture content of the tablets at 25 degrees C/60%RH, 30 degrees C/60%RH and 40 degrees C/75%RH were 2.3,2.4, and 2.9%, respectively. The tablet equilibrium moisture content, degradation rate of unpackaged product, and the moisture barrier properties of the packages were used to predict the stability of the packaged product. The physical and chemical stability (HPLC assay) of the products were measured after 2,4,6,8,12, and 24 weeks at ICH conditions. The Containers-Permeation(1) of polyvinyl chloride blisters, cyclic olefin blisters, aclar blisters, cold-form aluminum blisters was 0.259, 0.040, 0.008 and 0.001 mg per blister per day, respectively. At 6 months at 40 degrees C/75%RH, the percent active was 84% in polyvinyl chloride blisters, 91% in cyclic olefin blisters, 97% in aclar blisters, 100% in cold-form aluminum blisters and 99% in an high density polyethylene bottle with a foil induction seal. The stability results for the packaged product were fairly consistent with the predictions based on the moisture sensitivity of the product and the moisture barrier properties of the respective package. To gain a better prediction, the flux value determined by the Containers-Permeation procedure was adjusted for the internal moisture concentration of the blister.

Application of multiple response optimization technique to extended release formulations design

The purpose of the present study was to apply response surface methodology and multiple response optimization utilizing superimposed contour diagrams to design extended release formulations with a preplanned release profile. Bumetanide solution was layered on sugar pellets followed by coating with various coating formulations according to a central composite statistical design using a Glatt GPCG 1 Wurster Fluid Bed. The coated pellets were tested for their release profiles and the percent of drug released after 1, 4 and 8 h were used to describe and optimize the release process. Statistical models describing the percent bumetanide released after 1, 4 and 8 h were developed and the corresponding contour diagrams were superimposed to predict the coating formulation parameters expected to produce target release profile. The pellets coated with the designed coating formulation were tested for their release profiles in comparison to the target profile. According to the model-independent approach using similarity factor (F2), the dissolution profile of the designed formulation and the expected target profile were found to be similar. It was concluded that response surface methodology and multiple response optimization could be successfully used to design and optimize extended release formulations with desired preplanned release profile.

SYNTHESIS AND ANTIBACTERIAL ACTIVITY OF NEW 4H-PYRANO [3,2-h]QUINOLINES AND FUSED DERIVATIVES

The starting materials, 2-amino-3-cyano-4-(3,4,5-trimethoxyphenyl)-4H-pyran0[3,2-hlquinoline 1 and ethyl-2-amino-4-(3,4,5-trimethoxyphenyl)-4H-pyrano [3,2-hlquinolin-3-carboxylate 2 were synthesised from 8-hydroxyquinoline and a-cyano-3,4,5-trimethoxycinnamonitrileand/or ethyl-a-cyano-3,4,5-trimethoxy-cinnamatre respectively. In order to construct a third heterocyclic ring 1 and 2were condensed with ethyl bromoacetate, formarnide, carbon disulfide to afford pyrrolo-, pyrimido- and thiazinopyranoquinolines 3-6respectively. The S-alkylated products 7 and 8 were obtained by the effect of chloroacetonitrile and/or ethyl chloroacetate on thiazinopyranoquinoline derivative 6. The attempt of cyanomethylation of the amino functional group of 1 to yield 10 with chloroacetonitrile in AcOHIAcONa failed and instead, pyridopyranoquinoline derivative 9 was obtained which is visualized to occur via cyclization of the initially formed acetylarnino derivative by nucleophilic attack on the cyano group. Acetylation of 1 and 2 with acetic anhydride afforded the mono- and di-acetyl derivatives 11a and 11b respectively. A plausible explanation to form the mono-derivative with 1 and the di-derivative with 2 is the higher deactivating effect of the cyano function over that of the carboxyethyl group. Furoylation of 1 and 2 was achieved by furoyl chloride to give 12a and 12b respectively. The structural features of pyranoquinoline 2 were inferred from its microanalysis and spectral data such as IR,1H-NMR and MS as well as its chemical reactions, as a bifunctional compound with carbon nucleophiles namely, phenyl isothiocyanate and nitrogen nucleophilic species namely, p-toluidine, benzylamine, aniline and hydrazine hydrate to give pyrimidopyranoquinoline derivative 13, carboxamides 14a-c and carboxyhydrazide 15 respectively. When the hydrazide 15 was treated with carbon disulfide inpresence of KOH, it afforded the potassium salt 16 which was submitted to react with hydrazine hydrate at room temperature to give 17. The hydrazido group of 15was utilized to construct heterocyclic moieties attached to postion-3 of the pyranoquinoline structure. Thus, the reaction of the carboxyhydrazide15 with phenyl isothiocyanate, acetylacetone, and benzoylacetone resulted in the formation of 18, 19a and 19b respectively. Ethyl carbazate as a typical mesophile reacted with 2 to afford a fused tetracyclic product triazepinopyranoquinoline 20 via cyclization of the initially formed hydrazide. Among sixteen compounds screened against E. coli and S. aureus respectively,compounds 2 and 14c show a high order of antibacterial activity against both bacteria. 12b is strongly potent against Staphylococcus aureus.

A severe genotype with favourable outcome in very long chain acyl-CoA dehydrogenase deficiency

A patient with very long chain acyl-CoA dehydrogenase (VLCAD) deficiency is reported. He had a severe neonatal presentation and cardiomyopathy. He was found to be homozygous for a severe mutation with no residual enzyme activity. Tandem mass spectrometry on dried blood spots revealed increased long chain acylcarnitines. VLCAD enzyme activity was severely decreased to 2% of control levels. Dietary management consisted of skimmed milk supplemented with medium chain triglycerides and L-carnitine. Outcome was good and there was no acute recurrence.

Predicting dissolution via hydrodynamics: salicylic acid tablets in flow through cell dissolution

A model was established for the dissolution of non-disintegrating salicylic acid tablets as a function of hydrodynamic conditions in the Flow Through Cell system (USP Apparatus 4). The approach was to model the dissolution rate of the material as a function of the Reynold's number, the dimensionless engineering term that describes the degree of turbulence. The dissolution rate of USP calibrator salicylic acid tablets was measured as a function of tablet size, orientation within the cell, dissolution media flow rate, and cell size. All of these variables were found to have an effect on dissolution rate, consistent with theory. An equation to predict this dissolution was established as: N(SH)=-21.1+12.6xN(RE)(0.5), R(2)=0.99; 10<N(re)<292.

Liquid chromatographic method for the analysis of buspirone HCl and its potential impurities

An accurate, reproducible, and sensitive method for the determination of buspirone HCl and its potential impurities is developed and validated. The validated liquid chromaography method is conducted to meet the Food and Drug Administration/ International Conference on Harmonization requirements for the analysis of buspirone HCI in the presence of its impurities. Five buspirone HCI potential impurities, including 1-(2-pyrimidinyl)-piperazine (I), propargyl chloride (II), 3,3'-tetramethylene glutarimide (III), propargyl glutarimide (IV), and the Mannich base-condensate of I-IV fumarate (V), are separated using a microBondapack C18 column by gradient elution with a flow rate 2.0 mL/min. The initial mobile phase composition is 90:10 (v/v) 10mM KH2PO4 (pH 6.1)-acetonitrile. After a 1-min initial hold, a linear gradient is performed in 26 min to 35:65 (v/v) 10mM KH2PO4 (pH 6.1)-acetonitrile. The samples are detected at 210 and 240 nm using a photo-diode array detector. The linear range of detection for buspirone HCI was between 1.25 ng/microL and 500 ng/microL, with a limit of quantification of 1.25 ng/microL. The linearity, range, peak purity, selectivity, system performance parameters, precision, accuracy, and robustness for all of the impurities were also shown to have acceptable values.

Stability-indicating high-performance liquid chromatographic assay of buspirone HCl

The United States Pharmacopoeia high-performance liquid chromatographic (HPLC) assay method of buspirone is not able to discriminate buspirone from its degradation products. The purpose of this work is to develop a sensitive, selective, and validated stability-indicating HPLC assay for the analysis of a buspirone hydrochloride in a bulk drug. Buspirone HCI and its potential impurities and degradation products are analyzed on an Ultrasphere C18 column heated to 40 degrees C using a gradient program that contains monobasic potassium phosphate buffer solution (pH 6.9) and acetonitrile-methanol mixture (13:17) of 35% for 5 minutes, then increased to 54% in 5.5 minutes. The samples are monitored using a photo-diode array detector and integrated at 244 and 210 nm. The stress testing of buspirone HCI shows that buspirone acid hydrochloride is the major degradation product. The developed method shows a separation of buspirone degradation product and its potential impurities in one run. The stability of buspirone HCI is studied under accelerated conditions in order to provide a rapid indication of differences that might result from a change in the manufacturing process or source of the sample. The forced degradation conditions include the effect of heat, moisture, light, acid-base hydrolysis, sonication, and oxidation. The compatibility of buspirone HCI with some pharmaceutical excipients is studied under stress conditions. The linear range of buspirone HCI is between 5 and 200 ng/microL with a limit of quantitation of 2.5 ng/microL. The intraassay percentage deviation is not more than 0.38%, and the day-to-day variation was not more than 0.80%. The selectivity, repeatability, linearity, range, accuracy, sample solution stability, ruggedness, and robustness show acceptable values.

Modeling of a roller-compaction process using neural networks and genetic algorithms

In this study, roller-compaction of acetaminophene was studied to model the effect of binder type (hydroxypropyl methyl cellulose (HPMC), polyethylene glycol (PEG), Carbopol), binder concentration (5, 10 and 20%), number of roller-compaction passes (one or two), and extragranular microcrystalline cellulose addition on the properties of compressed tablets. Forty-two batches resulted from the experimental design. The artificial neural network methodology (ANN) along with genetic algorithms were used for data analysis and optimization. ANN and genetic models provided R2 values between 0.3593 and 0.9991 for measured responses. When a set of validation experiments was analyzed, genetic algorithm predictions of tablet characteristics were much better than the ANN. Optimization based on genetic algorithm showed that using HPMC at 20%, with two roller-compaction passes would produce mechanically acceptable acetaminophene tablets. PEG and carbopol would also produce acceptable tablets perhaps more suitable for sustained release applications. Using PEG as a binder had the additional advantage of not requiring an external lubricant during tablet manufacturing.

Influence of pH and plasticizers on drug release from ethylcellulose pseudolatex coated pellets

Six potential plasticizers for an ethylcellulose (EC) pseudolatex coating system (Aquacoat) were evaluated at three levels (25, 30, and 35%) to study the influence of these additives on the release of a model compound, propranolol hydrochloride, from pellets in two different media, dilute HCl and phosphate buffer, pH 7.4. For the majority of the plasticizers, the release rate decreased when larger amounts of plasticizer were incorporated into the coating. However, for the plasticizers dibutyl sebacate and dibutyl adipate, no further reduction in the release rate was observed following dissolution testing in dilute HCl when the level of plasticizer was increased from 30 to 35%. This suggests that the saturation capacity of these plasticizers in the film coating had been exceeded. The media pH was found to influence the dissolution characteristics of the coatings. Faster release rates as well as earlier curve inflection points and T50% values were observed for plasticizers evaluated in phosphate buffer. All plasticizers used were independent of pH. Correlation of the dissolution results with properties of free films indicated that slower release (more complete film formation) is associated with softer and weaker films with greater elongation.

Processing considerations for an EC latex coating system: influence of curing time and temperature

The influence of curing time and curing temperature for a commercially available ethylcellulose latex coating dispersion (Aquacoat) were evaluated using response surface methodology. Levels for the factor curing time ranged from 30 to 300 minutes while levels for curing temperature ranged from 45 degrees to 75 degrees C. Responses, A, kappa, and gamma, were derived from regression analysis of the dissolution profiles and correspond to the maximum amount of drug released over the 12 hour sampling period, the rate of release, and the inflection point of the dissolution profile, respectively. The nature of the response surface was dramatically influenced by the plasticizer incorporated into the coating formula. When dibutyl sebacate was employed as the plasticizer, faster release resulted (higher A and kappa values, lower gamma values) when samples were exposed to higher curing temperatures or were stored for longer periods of time. Paradoxically, when tributyl citrate was used as the plasticizer, slower release resulted when samples were exposed to more rigorous conditions. Overall, curing temperature had a more dramatic effect than curing time.

Characterization of esterase and alcohol dehydrogenase activity in skin. Metabolism of retinyl palmitate to retinol (vitamin A) during percutaneous absorption

Retinyl palmitate, a widely used ingredient in cosmetic products, is promoted for its beneficial effects on the appearance of skin. Previous studies suggest that enzymes are available in skin to metabolize this ingredient during skin absorption. Esterase activity hydrolyzes retinyl palmitate to retinol (vitamin A), which is oxidized in many tissues to retinoic acid primarily by alcohol dehydrogenase. The activities of esterase and alcohol dehydrogenase were characterized in hairless guinea pig skin by using flow-through diffusion cells and radiolabeled model compounds (methyl salicylate and benzyl alcohol) previously shown to be metabolized by these enzymes. Methyl salicylate was hydrolyzed by esterase to a greater extent in viable skin than in nonviable skin. Glycine conjugation of salicylic acid and benzoic acid occurred only in viable skin. The metabolism of methyl salicylate and benzyl alcohol occurred to a greater extent in male guinea pig skin than in female guinea pig skin. The percutaneous absorption of both radiolabeled compounds was similar in viable and nonviable skin. About 30 and 18% of topically applied retinyl palmitate were absorbed from an acetone vehicle by hairless guinea pig skin and human skin, respectively. Less than 1% of the applied dose of this lipophilic compound diffused from skin into the receptor fluid. Retinol was the only detectable metabolite of retinyl palmitate in both hairless guinea pig and human skin. In human skin, 44% of the absorbed retinyl palmitate was hydrolyzed to retinol. The use of retinyl palmitate in cosmetic formulations may result in significant delivery of retinol into the skin.

Development and evaluation of a monolithic floating dosage form for furosemide

The poor bioavailability of orally dosed furosemide (60%), a weakly acidic drug, is due to the presence of a biological window comprised of the upper gastrointestinal tract. The purpose of the present study was to develop and optimize in vitro a monolithic modified-release dosage form (MMR) for furosemide with increased gastric residence time and to evaluate the in vivo performance of the dosage form. The principle of floatation was used to restrict the MMR to the stomach. A two-factor three-level full factorial experimental design was employed for formulation development. A flow-through cell was designed to evaluate in vitro dissolution parameters. Quadratic regression models indicated the polymer viscosity and polymer:drug ratio to be significant (p < 0.05) formulation factors in determining the duration of buoyancy and the release profile. Statistical optimization using response surface methodology with certain physiological constraints relating to gastric emptying time predicted an optimal MMR. In vivo evaluation of the optimized MMR in beagle dogs resulted in a significant increase (p < 0.05) in the absolute bioavailability for the MMR dosage form (42.9%) as compared to the commercially available tablet (33.4%) and enteric product (29.5%). Significant in vitro/in vivo correlations (p < 0.05) were obtained for the MMR using deconvolution analysis normalized for bioavailability. The floating dosage form was found to be a feasible approach in delivering furosemide to the upper gastrointestinal tract to maximize drug absorption.

Effect of mode of incorporation of disintegrants on the characteristics of fluid-bed wet-granulated tablets

A full factorial experimental design was employed to investigate the effects of mode of disintegrant incorporation and concentration in wet-granulated paracetamol tablets manufactured by top-spray fluid-bed. Disintegrants (croscarmellose sodium, sodium starch glycolate, or crospovidone) were incorporated either intragranularly, extragranularly, or distributed equally between the two phases. The results were analysed by a general quadratic equation and response surfaces generated. On examining the results for dissolution studies the combined mode resulted in significantly faster dissolution rates than did the extragranular mode which, in turn, was superior to the intragranular mode of inclusion. These results were reflected in the disintegration studies where the combined mode exhibited the shortest disintegration times for all the disintegrants. Tablet crushing strength was not affected by the mode of incorporation of concentration of the disintegrants. Main as well as interaction effects between the types, mode of incorporation and percent disintegrant employed were significant (P < 0.05) for disintegration time and percent release at 15 min. Croscarmellose sodium exhibited the shortest while crospovidone displayed significantly (P < 0.05) longer disintegration times. Formulations containing crospovidone did not meet official compendial (USP XXII) requirements of 80% in 30 min. In general, croscarmellose sodium and sodium starch glycolate were found to be less sensitive to the mode of incorporation than crospovidone.

Biopharmaceutic evaluation of furosemide as a potential candidate for a modified release peroral dosage form

An attempt was made to evaluate some of the criteria for developing a modified release peroral dosage form for furosemide which has a poor bioavailability when given in the conventional peroral dosage forms. The pathway of absorption for furosemide was studied ex vivo employing the Wilson-Wiseman test. Passive absorption was found to be the predominant mechanism of transport across the ileum of the guinea pig followed by active transport to the extent of about 17%. The in situ procedure to study the extent of absorption of furosemide from the various sites in the lumen of the gastrointestinal tract of the rat indicated the stomach to be the major site of absorption followed by the duodenum. It is hence postulated that due to the site-specificity and mechanism of absorption a peroral modified release dosage form having a longer gastric residence time could possibly increase the bioavailability of furosemide.

Pharmacokinetics and bioavailability of papaverine HCl following intravenous, peroral, rectal, vaginal, topical and buccal administration in beagle dogs

This in vivo study was designed to obtain bioavailability data and a definite pharmacokinetic profile of papaverine HCl in Beagle dogs following intravenous (IV), peroral (PO), rectal, vaginal, topical, and buccal administration of different papaverine HCl formulations. Blood samples were analyzed by high-performance liquid chromatography. The pharmacokinetic parameters were determined using either a curve fitting program (RESID) or a compartment model independent program (AUC-RPP). The plasma concentration-time profiles show that papaverine HCl pharmacokinetics is best described by an open two-compartment model. The absolute bioavailability of papaverine HCl was determined to be 57.2 per cent, 25.2 per cent, 53.2 per cent, 3.2 per cent and 7.5 per cent, respectively, following P.O., rectal, vaginal, topical and buccal administration.

In vitro/in vivo evaluation of hydrochlorothiazide in experimental hydrochlorothiazide/triamterene combination tablets in beagle dogs

The purpose of this study was to compare experimental formulations containing hydrochlorothiazide (CAS 58-93-5)/triamterene (HCT/TRI) in vitro and in vivo to a commercial tablet formulation (standard). The beagle dog was verified as a good model and was used for the in vivo studies. The commercial tablet and the experimental fast release formulation (FR) resulted in 100% release of HCT within 30 min in dissolution tests, whereas, the slow release formulation (SR) released only 54% HCT after 4 h. Relative bioavailability of the FR and SR formulations were 82 and 41%, respectively, compared to the commercial tablet. The experimental results indicate that HCT absorption occurs throughout the small intestine.

Pharmacokinetics of papaverine HCl upon intravenous route of administration in old and young beagle dogs

This in vivo study was designed to compare the pharmacokinetics of papaverine HCl in young and old Beagle dogs following intravenous (i.v.) administration of papaverine HCl. Blood samples were analyzed by high performance liquid chromatography. The pharmacokinetic parameters were first determined using a curve fitting program (RESID), and then evaluated by SAS statistics. The plasma concentration-time profiles show that papaverine HCl pharmacokinetics is best described by an open two-compartment model. The only age-dependent significant difference in pharmacokinetic behavior between young and old Beagle dogs was found concerning the distribution rate constants.

In vitro skin absorption and metabolism of benzoic acid, p-aminobenzoic acid, and benzocaine in the hairless guinea pig

The percutaneous absorption and metabolism of three structurally related compounds, benzoic acid, p-aminobenzoic acid (PABA), and ethyl aminobenzoate (benzocaine), were determined in vitro through hairless guinea pig skin. Benzocaine was also studied in human skin. Absorption of benzocaine was rapid and similar through both viable and nonviable skin. The absorption of the two acidic compounds, benzoic acid and PABA, was greater through nonviable skin. A small portion (6.9%) of absorbed benzoic acid was conjugated with glycine to form hippuric acid. Although N-acetyl-benzocaine had not been observed as a metabolite of benzocaine when studied by other routes of administration, both PABA and benzocaine were extensively N-acetylated during percutaneous absorption. Thus, the metabolism of these compounds should be considered in an accurate assessment of absorption after topical application.

Maintenance of skin viability during in vitro percutaneous absorption/metabolism studies

The assessment of cutaneous metabolism during in vitro percutaneous absorption studies requires maintenance of the viability of the skin section. With the use of flowthrough diffusion cells, Eagle's minimal essential medium (MEM), Hepes-buffered Hanks' balanced salt solution (HHBSS), or Dulbecco modified phosphate-buffered saline (DMPBS), acting as receptor fluids, were able to sustain aerobic and anaerobic glucose utilization, testosterone and estradiol metabolism, and histopathological appearance of perfused rat skin sections for 24 hr. Fetal bovine serum supplements were not required for survival and appeared to inhibit the extraction of the metabolite estrone from the receptor fluid fractions in estradiol absorption/metabolism experiments. The use of phosphate-buffered saline (PBS) resulted in elimination of aerobic and anaerobic glucose utilization in 12 hr and declining appearance of steroid metabolites in receptor fluid fractions during the 24-hr percutaneous absorption/metabolism studies. Histopathological examination of skin sections perfused with PBS for 24 hr showed autolysis of the viable epidermis and dermis. The results demonstrate that an appropriate receptor fluid, such as MEM, HHBSS, or DMPBS, is required for percutaneous absorption studies in which cutaneous metabolism of the penetrating compound is to be considered.

Apparatus for studying the disintegration of tablet coatings

A new apparatus has been designed to assess rates of disintegration of tablet coatings and the availability of coated tablet contents. Random movement of the coated tablet in a known volume of mildly turbulent disintegrating fluid at a standard temperature is achieved in a perforated Perspex drum made to revolve slowly in the fluid which moves up and down in its container at the same time. The procedure eliminates the tendency for coatings to stick together or to the grid during a test, which is seen with present pharmacopoeial designs and which causes large variability in the results.