Time Course of Dehydrating Effects of Isosorbide on Experimentally Induced Endolymphatic Hydrops in Guinea Pigs

Osmotic diuretics are therapeutic agents used to reduce endolymphatic hydrops. However, glycerol-induced change in endolymph volume is followed by a rebound phenomenon. In this study, we investigated the rebound phenomenon occurring with isosorbide, an osmotic diuretic used as a therapeutic agent for Ménière's disease in Japan. Forty guinea pigs underwent surgical obliteration of the endolymphatic sac. Thirty received isosorbide orally 1 month after surgery. These animals were sacrificed 3, 6, or 12 h after isosorbide intake. The remaining 10 animals served as controls. Quantitative assessment of changes in the endolymphatic space was performed light-microscopically. Isosorbide reduced cochlear endolymph volume, with a peak reduction 6 h after intake. Thereafter, no prominent rebound phenomenon was noted. Clinically, since isosorbide is orally administered every 8 h, rebound phenomenon need not be considered in the treatment with isosorbide.

Excipient crystallinity and its protein-structure-stabilizing effect during freeze-drying

The relationship between mannitol crystallization during freeze-drying and its effects on stabilizing protein structures was studied using lysozyme, bovine serum albumin, ovalbumin, beta-lactoglobulin and lactate dehydrogenase as model proteins. FT-IR analysis of the protein secondary structure indicated perturbation of both alpha-helix and beta-sheet regions in freeze-drying without cosolutes, whereas the proteins retained most of their native structure in co-lyophilization with sucrose. Mannitol protected the protein structure to different degrees depending on the crystallinity. The combination of mannitol with potassium phosphate buffer reduced the mannitol crystallinity and the structural changes occurring during freeze-drying, whereas mannitol by itself showed little stabilizing effect. Heat-treatment of the frozen solutions at -10 degrees C resulted in a higher mannitol crystallinity and a smaller stabilizing effect in freeze-drying. The secondary structure perturbation was mostly reversible in rehydrated solutions. The varied structure-stabilizing effects of mannitol paralleled its effects on maintaining lower concentrations of enzyme activity during freeze-drying. These results confirm the contribution of molecular interactions between amorphous excipients and proteins (e.g. hydrogen bonding) to structure stabilization during freeze-drying.

Deoxycholate-hydrogels: novel drug carrier systems for topical use

Na-deoxycholate (Na-DOC) forms a viscous thixotropic gel when in contact with excess buffer systems. The resulting gels have been tested as novel drug carrier systems for topical use. The influence of differing amounts of mannitol, glycerol and xylitol on the viscous modulus (G"/Pa) was evaluated by oscillatory measurements. Na-DOC (0.5%) in phosphate buffered saline (PBS) with 5% mannitol was chosen as an optimised formulation, taking into account viscosity, distribution and appearance. The release rate of the model drug rutin through an artificial membrane was higher than those from hydroxyethylcellulose- (HEC) and sodium polyacrylate (NaC934)-gels; permeation through excised rat skin was also highest for the Na-DOC systems. The results indicate that Na-DOC significantly increases the membrane permeability. The microbial stability was in the same range as HEC- and NaC934-gels, making a preservation necessary. Na-DOC-gels are novel low molecular weight, multifunctional drug carriers, which also act as penetration enhancers. Their thixotropy is an additional advantage for better application to large skin areas, nasal, vaginal and buccal membranes. Therefore, Na-DOC-gels can be considered promising, alternative drug carrier systems for topical pharmaceutical as well as cosmetic use.

Influence of particle size, air flow, and inhaler device on the dispersion of mannitol powders as aerosols

PURPOSE

To study the effect of particle size, air flow and inhaler type on the dispersion of spray dried mannitol powders into aerosols.

METHODS

Mannitol powders were prepared by spray drying. The solid state properties of the powders were determined by laser diffraction, X-ray powder diffraction, scanning electron microscopy, freeze fracture, Karl Fischer titration and gas pycnometry. The powders were dispersed using Rotahaler and Dinkihalerg, connected to a multistage liquid impinger at different air flows.

RESULTS

Three crystalline mannitol powders with primary particle size (MMD) 2.7, 5.0, 7.3 microm and a similar polydispersity were obtained. The particles were spherical with a density of 1.5 g/cm3 and a moisture content of 0.4 wt.%. At an air flow of 30 L/min all the powders were poorly dispersed by both inhalers. With the Rotahaler increasing the flow (60-120 L/min) increased the fine particle fraction (FPF) in the aerosols for the 2.7 microm powder, and decreased the FPF for the 7.3 microm powder; whereas the FPF for 5.0 microm powder was unaffected. With the Dinkihaler, all the powders were near complete dispersion at > or = 60 L/min.

CONCLUSIONS

The FPF in the mannitol powder aerosols was determined by an interplay of the particle size, air flow and inhaler design.

Mannitol and cardiac surgery

Mannitol is widely used in all fields of medicine, due to its beneficial actions on the kidney and brain. Mannitol has been extensively used in cardiac surgery since its infancy, and remains in common usage to day. Mannitol is mainly used for its effects on the kidneys, but it has actions on the brain, lungs, heart, gastrointestinal tract and the red cell. Mannitol also has effects on free radicals and nitric oxide. As with virtually all treatments in medicine and surgery its use is not immune from side effects. The medical literature on mannitol over the past 30 years is considered.

Incidence of perforation and other mechanical complications during dual active fixation

The intraoperative and early postoperative mechanical complications of a procedure combining an atrial screw-in lead and a ventricular screw-in lead insertion were prospectively evaluated. The procedure was performed in 119 consecutive patients (mean age 69 +/- 8 years), at first implant in 100 patients and at reoperation in 19. Nine patients had previously undergone cardiac surgery and three underwent transvenous ventricular defibrillator implantation. The double sets of leads were introduced through 2 separate veins in 5 cases, through a single venous route in 114 cases, using a percutaneous approach in 75 cases and a venous cutdown in 49, and a guidewire procedure following the venotomy in 19. The screw was mannitol coated in 102 cases, exposed in 111, and extendable/retractable in 25. The fixation of the ventricular lead was performed at the apex in 108 cases, at the outflow tract in 11, and was followed by the fixation of the atrial lead at the appendage in 112 cases and at the lateral wall in 7 cases. The lead positioning and fixation were successful at first attempt in 103 cases and after repeated lead manipulation in 19 cases. The rotational torque could be transferred to the helix in all cases except in one patient who required a second vein puncture. Unintentional fixation in the ventricular chamber with subsequent failure to remove the lead occurred in one patient. Reoperation for lead dislodgment was required in two patients. In one patient, symptomatic pericarditis with pericardial effusion was observed 1 day after the procedure and resolved spontaneously. Dual active fixation is feasible with a low incidence of mechanical complications.