Percentage Buoyancy Research Articles

Sustained delivery of propranolol by using multiparticulate gastroretentive drug delivery system

PURPOSE: Gastroretentive systems can significantly prolong the gastric residence time of drugs. If a drug is stable in gastric acid, prolonged gastric retention improves bioavailability. The objective of the present investigation was to develop an extended and controlled release composition and formulation of propranolol using expandable, gelling, swellable hydrocolloid polymer along with mineral oil. METHODS: A formulation was prepared without using mineral oil by conventional ionotropic gelation method. All other formulations of oil entrapped floating gel beads of propranolol hydrochloride were prepared by using emulsion gelation method in which sodium alginate was used as a gelling agent and mineral oil was used to impart buoyancy to the formulation Spherical gel beads were formed instantaneously. The prepared beads were evaluated for diameter, surface morphology, encapsulation efficiency and drug release. RESULTS: Low concentration of oil containing formulation exhibited greater release of drug. As the concentration of oil increases, drug release decreases to certain extent. Percentage buoyancy of floating propranolol hydrochloride gel beads was found satisfactory. The highest mean diameter was observed in the formulation with 30% of mineral oil. The formulation with 35% of mineral oil had the highest drug loading and scanning electron microscopy revealed that the beads were spherical in shape with rough surfaces. CONCLUSION: Oil entrapped gel beads can be used as floating drug delivery system for extended drug release for both local and systemic drug delivery. Keywords: Floating drug delivery system; Emulsion gelation; Sodium alginate; Mineral oil; Propranolol hydrochloride.

Buoyancy studies of three morphs of the Antarctic fish Trematomus newnesi (Nototheniidae) from the South Shetland Islands

Phenotypic plasticity, a widespread phenomenon in boreal freshwater fishes, is less apparent in the marine realm and the organism–environment interactions producing this variation are undetermined. A sample of 40 specimens of Trematomus newnesi, an inshore Antarctic fish from King George/25 de Mayo Island in the South Shetlands, was composed of 52.5% typical morphs, 27.5% large-mouth morphs and 20% intermediate morphs. Measurements of percentage buoyancy on the morphs of this sample were 3.73, 3.84 and 3.83%, respectively with no significant differences among means. Both mean dry skeletal weight as a percentage of body weight and mean oral jaw weight as a percentage of dry skeletal weight were significantly greater in large-mouth morphs compared to typical morphs. Diversification in head and jaw morphology is not accompanied by diversification in ecology as represented by buoyancy and, in spite of external appearances, measurements of buoyancy offer no support for the hypothesis that the large-mouth morph is more benthic than the typical semipelagic morph. Although a trophic basis for this polymorphism is possible, it has not yet been documented. Our discussion centers on the status of key open questions regarding morphism and highlights areas requiring more research.

Geographic intraspecific variation in buoyancy within Antarctic notothenioid fishes

AbstractWe investigated intraspecific geographic variation in buoyancy by obtaining percentage buoyancy (%B) measurements for the Antarctic notothenioid speciesPleuragramma antarcticum,Trematomus hansoni,T. bernacchiiandGymnodraco acuticepsfrom both McMurdo Sound in East Antarctica and the South Shetland Islands in West Antarctica. Mean percentage buoyancies in these species ranged from 0.22–0.52% in the neutrally buoyantP. antarcticumto 3.34–3.67% in the benthicT. bernacchii. Dispersion (1 standard deviation) of percentage buoyancy (%B) values around the mean was ± 0.2–0.5 %B units for the entire sample. Although intraspecific differences in mean percentage buoyancy were statistically significant (P < 0.05) inP. antarcticumandT. hansoni, we consider these differences as normal variation without substantive biological significance. The dispersion in buoyancy measurements during adult life reflects the density of the fish and this may be influenced, in both the short- and long-term, by gut contents, nutritional condition, and reproductive state. Mitigation of the effects of these variables is not biologically realistic because they constitute normal aspects of the daily and yearly life cycles. The results of our measurements of buoyancy are consistent with what is known about the ecology of these four species and this is considered in the discussion.

Optimization Studies on Floating Multiparticulate Gastroretentive Drug Delivery System of Famotidine

The objective of this study was to optimize floating microballoons of famotidine by the emulsion solvent diffusion technique using central composite design. Formulations F1–F15 were prepared using three independent variables (pH of medium, drug: Eudragit® S100 ratio and ethanol : dichloromethane ratio) and evaluated for dependent variables (shape, percentage buoyancy, and encapsulation). The optimized formulation F9 was fractionated and a polymer combination of (Eudragit® S100 : Eudragit® L100-55, 9.5:0.5) resulted in microballoons that exhibited zero order release (94.73%) with 84.20% buoyancy at the end of the eighth hour when studied in the mesh-designed modified USP type II apparatus.

Effect of coexcipients on drug release and floating property of nifedipine hollow microspheres: A novel gastro retentive drug delivery system

AbstractA gastro retentive drug‐delivery system for nifedipine was developed by incorporating the drug in cellulose acetate hollow microspheres capable of floating on the gastric and intestinal fluid. The microspheres were prepared by solvent diffusion–evaporation technique in the presence of coexcipients like polyethylene glycol, dibutyl phthalate, and poly(ε‐caprolactone) using ethyl acetate as a dispersing solvent. Size of the microparticles depends upon the type and concentration of the excipient used. Microparticles exhibited floating properties on the simulated‐gastric fluid for >12 h. Their percentage buoyancy followed the rank order of: blank (no coexcipients) > dibutyl phthalate > polyethylene glycol > poly(ε‐caprolactone) after 15 h of floating. Release of nifedepine was enhanced by the addition of coexcipients. The drug release followed non‐Fickian transport in almost all formulations. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 486–494, 2006

Measurements of buoyancy for some Antarctic notothenioid fishes from the South Shetland Islands

Buoyancy was measured for 258 specimens representing 13 species of adult and sub-adult nototheniids, bathydraconids, and channichthyids from the South Shetland Islands. Measurements were expressed as percentage buoyancy (%B)=W water /W air ×102. There were no neutrally buoyant species and mean values for %B were 3.07–6.11%, with channichthyids at the low end and benthic nototheniids and bathydraconids at the high end. All species showed an ontogenetic decrease in %B with increasing body weight. With the exception of Champsocephalus gunnari, there was no sexual dimorphism in %B within this sample. With some exceptions, values for %B were consistent with life-history information. Sub-adult Dissostichus mawsoni were not neutrally buoyant, as are large adults. Notothenia rossii had a significantly lower %B than closely related N. coriiceps. Benthic Gobionotothen gibberifrons had a lower %B than semipelagic Lepidonotothen larseni. Although they exhibit some diversification in life history, the four channichthyids in the sample were similar in %B. Neutral buoyancy is rare in notothenioids and may be confined to a single nototheniid clade.