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Body fluids and electrolytes
Published in Peate Ian, Dutton Helen, Acute Nursing Care, 2020
Osmosis is the passive movement of water across a selectively permeable membrane, from an area of lower solute concentration to an area of higher solute concentration. The membrane is fully permeable to water but selectively permeable to solutes. Osmosis ceases when there has been enough fluid movement to equalise the solute concentration on either side of the membrane. In clinical practice, you may hear the expression ‘water follows salt’ (see Figure 4.3). In practice, this means that water can flow easily across cell membranes if the solutions on either side cease to be isotonic, as occurs in dehydration.
Oxidative Properties of the Skin: A Determinant for Nickel Diffusion
Published in Jurij J. Hostýnek, Howard I. Maibach, Nickel and the Skin, 2019
Jurij J. Hostýnek, Katherine E. Reagan, Howard I. Maibach
Values for the main components of sweat have repeatedly been investigated over time, yielding increasingly accurate data reflecting improvements in analytical techniques. The main categories of solutes are discussed here. Table 3.1 lists the prevalent ranges; they are approximations, because values are unavoidably subject to variation even in normal subjects due to the type of stress applied for sweat stimulation, environmental and individual temperature, environmental humidity, diet and nutritional status, age, gender, sweat rate, skin area of collection, local skin temperature, and muscular activity.
Toxicokinetics
Published in Frank A. Barile, Barile’s Clinical Toxicology, 2019
A solution is a chemically and physically homogeneous mixture of two or more substances in a liquid. Similarly, suspensions are pharmaceutical preparations of finely divided, insoluble solids dispersed in a liquid vehicle for oral, inhalation, or parenteral administration. The extent to which a solute dissolves in a liquid is referred to as solubility. Solubility is also described as the concentration of a compound in a solution that is in equilibrium with a solid phase at a specified temperature. For any defined solid chemical or drug, the degree of solubility is determined by the innate chemical characteristics of the solid and the temperature. Thus, solubility is constant for a solid in a particular solvent at a given temperature. In addition, different categories of solutions or suspensions are possible depending on the size of the dispersed particle.* Consequently, it is conceivable to formulate homogeneous solutions of solids, liquids, or gases (solute) in liquids (solvent). The concept can be further extended into the preparation of gases in gases and solids in solids. More detailed discussion of the chemical properties of true solutions, solute–solvent interaction, and dispersion systems can be obtained from the Suggested Readings, some of which present the reader with quantitative data on the behavior and properties of solutions). This section is concerned with basic definitions of solutes and solvents, the influence of temperature on solution stability, and the eventual movement of a dissolved substance toward absorption.
Transdermal delivery via medical device technologies
Published in Expert Opinion on Drug Delivery, 2022
Shubhangi Shukla, Ryan H. Huston, Blake D. Cox, Abhay R. Satoskar, Roger J. Narayan
While drugs come in innumerable structural combinations, one way to classify them easily is using two main characteristics which provide unique advantages or challenges to their use, specifically drug permeability and drug solubility; hence, these two traits define the Biopharmaceutics Classification System taxonomy [111]. Iontophoresis has been shown to benefit many drugs with varying combinations of these traits; however, the most challenging drugs to deliver are those with low permeability and low solubility. Compared to water-soluble drugs, iontophoresis has not been thoroughly researched for use with lipophilic/hydrophobic or otherwise water-insoluble drugs. The current research has been largely focused on delivery of drugs via iontophoresis using water-based buffers and water-soluble ions; however, the principle of electroosmosis clearly supports the penetration of nonpolar or uncharged molecules as well [100]. In addition, creative drug formulations can enhance iontophoretic delivery by (a) placing drugs in liposomes or micelles; (b) mixing solutes with surfactants, cosolvents, or complexion solutes; or (c) substituting the solvent altogether [112].
Development and optimization of osmotically controlled drug delivery system for poorly aqueous soluble diacerein to improve its bioavailability
Published in Drug Development and Industrial Pharmacy, 2020
Magdy I. Mohamed, Abdulaziz M. Al-Mahallawi, Sami M. Awadalla
Osmotic pump Controlled Release Preparation is a novel drug delivery system. It gains a vital interest in oral solid dosage form development chiefly because of their ability to deliver drugs at constant rates (zero-order release) independent of media pH and hydrodynamics of the surrounding media [14,15]. Osmosis can be defined as the spontaneous movement of a solvent from a lower solute solution to a solution of higher solute concentration through an ideal semi-permeable membrane, which is permeable only to the solvent but impermeable to the solute [16,17]. The preparation consists of the core that contained the active material, a semi-permeable membrane that coated the core and an orifice, produced by a micro drill or mechanically to release the active material. When the system is in the gastrointestinal tract, fluid enters into the preparation and dissolves the active material within the core [14,17]. Thus the pressure formed in the preparation induces a release of the solution at a slow but continuous rate [18,19]. Therefore, solubility is considered one of the most vital factors affecting the drug release kinetics from the osmotic pump. As well as Osmotic pressure is another vital factor that imbibes water inside the osmotic pump, and it is proportional to the concentration of the osmotic agent [14].
Sustained release formulation of Ondansetron HCl using osmotic drug delivery approach
Published in Drug Development and Industrial Pharmacy, 2020
Ramakant Gundu, Sanjay Pekamwar, Santosh Shelke, Santosh Shep, Deepak Kulkarni
Osmotic systems utilize the principle of osmotic pressure for the delivery of drugs [10]. Drug release from these systems is independent of pH and other physiological parameter to a large extent and it is possible to modulate the release characteristic by optimizing the properties of drug and system. Osmosis refers to the net movement of solvent molecules across a semipermeable membrane from higher to lower solute concentration [11]. Push–pull osmotic pump tablet characterized by swellable pull layer which pull the drug outside from osmotic pump after pushing by swellable push layer [12]. It is a bilayer tablet coated with a semi permeable membrane. The upper compartment contained the drug; lower compartment contained high viscosity polymers, osmogent and was connected to the outside environment via a small delivery orifice. Polyethylene oxide (around 50–70%) was most commonly used polymer in pull and push layer. The system also had the disadvantage of higher cost compare to other extended release products [13].