Sohair El-Shanawany

Sustained release of nitrofurantoin from inert wax matrixes

Abstract Sustained release nitrofurantoin granules containing stearic acid and glyceryl monostearate (matrix) were prepared using fusion, solvent evaporation or melt granulation techniques. The effect of Aerosil, Avicel, dibasic calcium phosphate dihydrate (Emcompress) and sodium chloride as channeling agents on the in vitro release of nitrofurantoin was investigated. The results obtained revealed that, with the granules prepared by the fusion method a sustained release pattern could be achieved contrary to those prepared by the other techniques. Moreover, all the selected channeling agents increased the extent of the drug release but with different rates depending upon their concentration and nature. The release of the drug was found to follow the Higuchi model with granules containing 0 and 5% channeling agents while, it followed first-order kinetics with those containing 10% of channeling agent. In vivo studies in humans revealed that the urinary excretion of nitrofurantoin from the test granules occurred over a sustained period from 2–8 hours after oral administration.

In vitro and in vivo evaluation of biologically synthesized silver nanoparticles for topical applications: effect of surface coating and loading into hydrogels

In the present study, silver nanoparticles (AgNPs) were synthesized via biological reduction of silver nitrate using extract of the fungus Fusarium verticillioides (green chemistry principle). The synthesized nanoparticles were spherical and homogenous in size. AgNPs were coated with polyethylene glycol (PEG) 6000, sodium dodecyl sulfate (SDS), and β-cyclodextrin (β-CD). The averaged diameters of AgNPs were 19.2±3.6, 13±4, 14±4.4, and 15.7±4.8 nm, for PEG-, SDS-, and β-CD-coated and uncoated AgNPs, respectively. PEG-coated AgNPs showed greater stability as indicated by a decreased sedimentation rate of particles in their water dispersions. The antibacterial activities of different AgNPs dispersions were investigated against Gram-positive bacteria (methicillin-sensitive and methicillin-resistant Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) by determination of the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs). MIC and MBC values were in the range of 0.93–7.5 and 3.75–15 µg/mL, respectively, which were superior to the reported values in literature. AgNPs-loaded hydrogels were prepared from the coated-AgNPs dispersions using several gelling agents (sodium carboxymethyl cellulose [Na CMC], sodium alginate, hydroxypropylmethyl cellulose, Pluronic F-127, and chitosan). The prepared formulations were evaluated for their viscosity, spreadability, in vitro drug release, and antibacterial activity, and the combined effect of the type of surface coating and the polymers utilized to form the gel was studied. The in vivo wound-healing activity and antibacterial efficacy of Na CMC hydrogel loaded with PEG-coated AgNPs in comparison to the commercially available silver sulfadiazine cream (Dermazin®) were evaluated. Superior antibacterial activity and wound-healing capability, with normal skin appearance and hair growth, were demonstrated for the hydrogel formulations, as compared to the silver sulfadiazine cream. Histological examination of the treated skin was performed using light microscopy, whereas the location of AgNPs in the skin epidermal layers was visualized using transmission electron microscopy.

Evaluation of sustained-release suppositories containing microencapsulated theophylline and oxyphenbutazone

Abstract Microencapsulation of theophylline and oxyphenbutazone using ethylcellulose was carried out by a simple coacervation method. To control the release of theophylline and oxyphenbutazone the microcapsule surfaces were modified by dry-blending each drug with a carboxyvinyl polymer by pulverization in an electrical mixer before encapsulation. Suppositories containing pure theophylline or oxyphenbutazone as well as microencapsulated theophylline and oxyphenbutazone were prepared by the fusion method. The release rate of theophylline and oxyphenbutazone decreased as the content of coacervation-inducing agent polyethylene was increased except at a concentration of 1% polyethylene in case of oxyphenbutazone microcapsules. The release rates of theophylline and oxyphenbutazone from suppositories containing these microcapsules were in accordance with the results of the dissolution rates of drugs. On the other hand, suppositories containing microcapsulated carboxyvinyl-polymer-modified drugs showed a pseudo-zero-order release profile. The surface modification of drug particles with carboxyvinyl polymer before encapsulation is a good method to prepare sustained release suppositories containing theophylline and oxyphenbutazone microcapsules.

Niosomes: A Strategy toward Prevention of Clinically Significant Drug Incompatibilities

Drug incompatibilities are considered as one of the most critical problems in intensive care units. In the current study, the ability of nanomaterials to prevent drug incompatibilities in clinical settings has been investigated. As a proof-of-concept, the ability of niosomes to prevent physical and chemical incompatibilities that occur upon mixing acyclovir and vancomycin during management of acute meningitis has been explored. Nanosized spherical particles loaded separately with either vancomycin or acyclovir, with high entrapment efficiency (ca. 46–56%), could be prepared, and sustained release of their entrapped cargoes have been demonstrated over time. We have shown that precipitation, degradation and loss of biological activity of drugs occurred upon mixing solutions of the free drugs. On the contrary, drugs loaded separately inside niosomal structures exhibited high stability, exceptional physical and chemical compatibilities for up to 48 h with complete preservation of the antimicrobial activity of vancomycin. This study opens a venue for a new spectrum of applications of nanomaterials in preventing clinically significant drug incompatibilities, aiming at the reduction of adverse reactions, cost and hospitalization period, and improvement of patient compliance and therapeutic outcomes.

Effect of different ointment bases on ocular disposition of ethylphenylephrine in rabbit eyes

Abstract The influence of vehicle composition on the ocular disposition of ethylphenylephrine, a mydriatic drug used for the treatment of wide-angle glaucoma, has been studied. The vehicles investigated consisted of a hydrocarbon base, an absorption base (10% lanolin in a paraffin base) and a water-soluble base (polyvinyl alcohol, PVA, 15% in water). The albino rabbit was chosen as the animal model. The disposition of the drug in conjunctiva, cornea, iris-ciliary body and aqueous humor of the rabbit was monitored at 1, 2 and 4 h post-installation using extraction technique. At the early time period (1 h post-administration) both oleaginous and water-soluble bases were judged to perform adequately in that they provided approximately the same drug concentrations in various ocular tissues at the aqueous vehicle. However, after 4 h, the oleaginous base provided the highest concentrations of drug in the conjunctiva. The water-soluble PVA formulation gave significantly lower levels in the conjunctiva and the cornea. At this same point, the absorption base containing lanolin produced the highest drug concentration in the cornea, iris-ciliary body and aqueous humor. Collectively, these data suggest that of the 3 bases studied, the oleaginous base and the absorption base show most promise as vehicles to extend the residence time of ethylphenylephrine in the eye. Obviously the final choice of vehicle will also be influenced by factors such as the physical and chemical stability of the drug in the formulation chosen and patient acceptance.