Water-soluble vehicles

The vehicle system of water-borne coatings can be divided into two categories water-emulsifiable vehicles and water-soluble vehicles. 

Water-emulsifiable vehicles contain emulsifiers that may act as plasticizers after film formation, affecting the hardness. Water-soluble vehicles usually contain a neutralizing amine, the primary purpose of which is to solubihze the resin. These amines can influence the drying properties as they tend to complex the metal drier, thus affecting the catalytic activity. Acceptable results are usually obtained with trialkylamines such as dim ethyl eth a n o1 amine, trimethyl amine, and aminomethylpropan o1 (7). 

Alternatively, short-contact anthralin therapy (SCAT) with application for 10 to 20 minutes of higher concentrations (1% to 5%) in water-soluble vehicles is effective with decreased local adverse effects. 

The amount of liquid in the rectum has been reported to be about 3 ml. This is small compared to the volume of fluid available throughout the GI tract when a drug is administered orally. Such a small volume of fluid can limit dissolution of drugs, particularly those with low aqueous solubility. It also may be a constraint to the rapid dissolution and release of compounds from water-soluble vehicles where dissolution of the vehicle is considered to be the rate-determining step in drug release from the vehicle. 

Drug solubility also affects the choice of suppository base or other vehicle. Generally, the drug should have little tendency to remain in the vehicle upon melting or dissolution. Therefore, it is usually suggested that water soluble drugs are best delivered from fatty vehicles and that more lipophilic compounds from water-soluble vehicles. 

Lucas, P. A., Laurencin, C., Syftestad, G. T., Domb, A., Goldberg, V. M., Caplan, A. I., and Langer, R., Ectopic induction of cartilage and bone by water-soluble proteins from bovine bone using a polyanhydride delivery vehicle, J. Control. Rel. In Press. 

In an attempt to formulate an anhydrous, but water-soluble, semisolid base for potential ophthalmic use, five bases were studied [279]. The nonaqueous portion of the base was either glycerin or polyethylene glycols in high concentrations. The matrix used to form the phases included silica, Gantrez AN-139, and Carbopol 940. Eye irritation results were not reported, but the authors studied representative bases from that research report and found them to be quite irritating in rabbit eyes. The irritation is believed to be primarily due to the high concentration of the polyols used as vehicles. 

A number of water-soluble calcium salts provide convenient vehicles for the administration of therapeutic anions. Probably the most widely encountered is the acetylsalicylate of soluble aspirin (patented 1935) the urea complex of calcium acetylsalicylate (water-solubility 231 gdm-3 at 310K, pH 4.8 (717)) is also widely used. Other examples include calcium bromide and bromolactobionate (sedatives), calcium 2-hydroxy-3-mercapto-l-propanesulfonateaurate(III) (chrysanol, antiarthritic), and calcium Af-carbamoylaspartate (tranquillizer). Calcium iron(II) citrate has been used to remedy iron deficiency - it has the advantage of being stable to air oxidation of the iron(II). The cyclamate anion is certainly not therapeutic, but is relevant here. 

Solid materials require special techniques prior to or during addition to diets. Materials that are soluble in water may be dissolved and added as described above for liquids. Non-water-soluble materials may require several preparatory steps. The test chemical may be dissolved in com oil, acetone, or other appropriate vehicle prior... 

The thesis that all lipid-soluble compounds basically penetrate faster than water-soluble ones cannot be supported in this absolute form. A lipophilic agent can penetrate faster or slower or at the same rate as a hydrophilic agent, depending on the vehicle used. 

Volatility High, but declines when part of mixture with water Solubility/miscibility Miscible with water, acetone, and most other vehicles... 

Solubility/miscibility Generally very soluble or miscible in water. Soluble in ethanol, com oil, and olive oil. Insoluble in mineral oil Biological considerations Surfactant. May cause micelle formation, with incumbent effects on bioavailability if included at concentrations of 1% or higher. May be associated with irritation if given intravenously or intramuscularly. Dogs have the peculiarity that Tweens injected parenterally induce the spontaneous systemic release of histamine. This response is particularly striking with IV injection, and therefore Tweens should not be used as components of IV vehicles in dogs... 

Elixirs are clear oral solutions in which the vehicle is a hydroalcoholic mixture containing potent or nauseating drugs. Elixirs are pleasantly flavored and attractively colored. The presence of hydroalcoholic vehicle in an elixir makes it possible to include both water-soluble and alcohol-soluble substances in solution. In comparison to syrups, elixirs are less sweet and less viscous because of lower sugar content. From the manufacturing aspects and from the stability standpoint, elixirs are favored over syrups. 

Ointments are semisolid preparations that are intended for external use. Ointments may contain either finely powdered drugs or their mixtures, liquids, and other drug forms incorporated into appropriate bases. They are applied to the skin for their physical effects as emollients (which make the skin more pliable), protectants, lubricants, and drying agents. Ointment bases are also used as vehicles in which to incorporate topical medications which exert specific effect. There are four types of ointment bases, namely, oleaginous, absorption, water removable, and water soluble bases. 

One can conclude that PVA hydrogels represent an efficient encapsulation vehicle for the studied porphyrins, both water soluble and non-water soluble. Their biocompatible, biodegradable, non-toxic, and non-carcinogenic nature makes them especially effective for pharmaceutical applications, but also for environmental uses, such as advanced wastewater... 

In flavoring liquid pharmaceutical products, the flavoring agent is added to the solvent or vehicle component of the formulation in which it is most soluble or miscible. That is, water-soluble flavorants are added to the aqueous component of a formulation and poorly water-soluble flavorants are added to the alcoholic or other nonaqueous solvent component of the formulation. In a hydroalcoholic or other multisolvent system, care must be exercised to maintain the flavorant in solution. This is accomplished by maintaining a sufficient level of solvent in which the flavorant is soluble. 

In most cases, ointments, suppositories, ophthalmic, and parenteral products assume the color of their ingredients and do not contain color additives. In addition to esthetics and the certification status of a dye, a formulation pharmacist must select the dyes to be used in a particular formula on the basis of the physical and chemical properties of the dyes available. Of prime importance is the solubility of a prospective dye in the vehicle to be used for a liquid formulation or in a solvent to be employed during a pharmaceutical process (such as when the dye is sprayed on a batch of tablets). In general, most dyes are broadly grouped into those that are water-soluble and those that are oil-soluble few, if any, dyes are both. 

Prodrugs provide a vehicle by which the bioavailablUity of a drug displaying poor water solubility can be enhanced or a method of targeting diseased areas of the body. Following uptake, the drug is frequently released by the action of metabolic enzymes. For example, the human enzyme believed to be primarily responsible for the rapid in vivo hydrolysis of valaciclovir to aciclovir has recently been isolated and characterized (Scheme 1.18). ... 

The experimental procedure below describes the uptake of ciprofloxacin into sphingomyelin (SPM)/Chol LUVs. Drug delivery vehicles prepared from SPM/Chol often exhibit greater efficacy than those prepared from DSPC/Chol (13). Included is a description of the Bligh-Dyer extraction procedure (78), which involves partitioning the lipid and water-soluble drug into organic solvent and aqueous layers, respectively. This is necessary because lipid interferes with the ciprofloxacin assay. 

A new class of water-soluble materials [10,11], was developed as a result of such design parameters that will be referred to as double substituted cationic cellulose ethers (DCEs). These materials contain both a cationic substituent and a hydrophobic substituent, attached to a cellulose ether backbone. The use of a double-substituted hydrophobe modified cationic polysaccharide is fundamentally different from current commercial vaginal formulations, which rely exclusively on nonionic or anionic vehicles. 

Contraceptive formulations based on available water-soluble polymers are used quite extensively and successfully. However, to meet the challenge of today s emerging health crisis, rationally designed water-soluble polymer vehicles are poised to play an important role in the arsenal against... 

If the substance has been dosed using a vehicle, the water solubility of the vehicle and the vehicle/water partition coefficient of the substance may affect the rate of uptake. Compounds delivered in aqueous media are likely to be absorbed more rapidly than those delivered in oils, and compounds delivered in oils that can be emulsified and digested, e.g., com oil or arachis oil are likely to be absorbed to a greater degree than those delivered in nondigestible mineral oil (liquid petrolatum). 

C. This could be attributed to the possible cross-linkages formed between the two polymers which thus restricted the movement of the drug molecules within the gel. The release of propranolol hydrochloride from the emulsion base, formulation D, was relatively low compared with all the hydrophilic polymeric gel formulations. This suggests that, for a water-soluble drug such as propranolol hydrochloride, polymeric-gel-based formulations are clearly the better vehicles for developing such dosage forms. 

Diazepam, lorazepam, and midazolam are used for preanesthetic medication and as adjuvants during surgical procedures performed under local anesthesia. As a result of their sedative, anxiolytic, and amnestic properties, and their ability to control acute agitation, these compounds are considered to be the drugs of choice for premedication. (The basic pharmacology of benzodiazepines is discussed in Chapter 22.) Diazepam and lorazepam are not water-soluble, and their intravenous use necessitates nonaqueous vehicles, which cause pain and local irritation. Midazolam is water-soluble and is the benzodiazepine of choice for parenteral administration. It is important that the drug becomes lipid-soluble at physiologic pH and can readily cross the blood-brain barrier to produce its central effects. 

Water Water is the primary raw material in pharmaceutical formulations. It is the most used vehicle since it is the major component of the human body. For many products, it is the main component, and, even in those containing non-water-soluble substances, water must be present. Depending on the product and the form of administration, lipophilic drugs are prepared as water-oil emulsions. 

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