Patch vehicles

Sensitization results are based on a human maximization test (103) usiag a petrolatum vehicle. The effect is expressed as the number of paneHsts responding over the total number of paneHsts tested and was 0/25 except for spearmint (0/32). That is, at the dose iadicated, the oils werenot irritating when tested ia a 48-h closed patch test ia humans. 

De Groot, A.C., Patch Testing Test Concentrations and Vehicles for 3700 Chemicals, 2nd ed. New York Elsevier Science Ltd May 1994. 

Besides the test substance, a positive control substance (a known skin irritant, 1% sodium lauryl sulfate in distilled water) and a negative control (untreated patch) are applied to the skin. When a vehicle is used for diluting, suspending, or moistening the test substance, a vehicle control patch is required, especially if the vehicle is known to cause any toxic dermal reactions or if there is insufficient information about the dermal effects of the vehicle. 

The positive control substance and vehicle control substance are applied to a gauze patch in the same manner as a liquid test substance. 

TEST GROUP (15) A. 0.1 ML Substance ID Closed Patch-48H B. 0.1 ml FCA ID Application of C. 0.1 ml Substance Substance + FCA ID Closed Patch-24H Substance Vehicle Closed Patch-24H Vehicle 0... 

The solubilization of a drug substance in monophasic liquid crystalline vehicles gives semisolid formulations which are preferably used for topical application (see Surfactant Gels and Transdermal Patches above). 

V f/T enfs - The primary purpose for an ophthalmic ointment vehicle is to prolong drug contact time with the external ocular surface. This is particularly useful for treating children, who may cry out topically applied solutions, and for medicating ocular injuries, such as corneal abrasions, when the eye is to be patched. Administer solutions before ointments. Ointments preclude entry of subseguent drops. 

A host of bioadhesive controlled release systems have been proposed in recent years. Among the most commonly studied applications of bioadhesive materials is the area of buccal controlled delivery [408], The buccal delivery of small peptides from bioadhesive polymers was studied by Bodde and coworkers [409], and a wide range of compositions based on poly(butyl acrylate) and/or poly(acrylic acid) gave satisfactory performance. Bioadhesive poly(acrylic add)-based formulations have also been used for oral applications [402,410] for the sustained delivery of chlorothiazide [410] and for a thin bioadhesive patch for treatment of gingivitis and periodontal disease [411]. Other bioadhesive applications of polyelectrolytes include materials for ophthalmic vehicles [412,413], and systems for oral [410,414,415-419], rectal [420,421] vaginal [422] and nasal [423] drug delivery. 

Membranous epithelial M cells are a part of the organized mucosa-associated lymphoid tissue (O-MALT). These cells are specialized for antigen sampling. Also, they are exploited as a route of invasion by several pathogens.39 M cells are concentrated in follicle-associated epithelial (FAE) tissue called Peyer s patches in the small intestine. As M cells carry out endocytotic transport, they can be potential vehicles for mucosal drug and vaccine delivery. 

Several children and one adult who had previous injections of vaccines or allergens in an aluminum-based vehicle showed hypersensitivity to aluminum chloride in a patch test (Bohler-Sommeregger and Lindemayr 1986 Veien et al. 1986). Dermal hypersensitivity to aluminum appears to be rare in humans. 

Petrolatum continues to be used quite extensively in dermatological applications, primarily for three purposes (1) as an inert patch testing base, (2) as a vehicle in the dermal application of pharmaceuticals, and (3) as a treatment product itself. 

Gammelgaard, B., Fullerton, A., Avnstorp, C., and Menne, T., In vitro evaluation of water and petrolatum as vehicles in chromate patch testing, Contact Dermatitis, 27, 317, 1992. 

Tosti, A., Vincenzi, C., Trevisi, P, and Guerra, L., Euxyl K400 incidence of sensitization, patch test concentration and vehicle, Contact Dermatitis, 33, 193, 1995. 

Following whole-cell patch clamp with demonstration of stable hERG current, control values taken followed by exposure of the cells to the vehicle, then each concentration of the test article from lowest to highest concentration and finally the positive control... 

Occlusion of the skin, seen with application of water-impermeable drug vehicles or patches, alters the rate and extent of toxicant absorption. As the skin hydrates, a threshold is reached where transdermal flux dramatically increases (approximately 80% relative humidity). When the skin becomes fully hydrated under occlusive conditions, flux can be dramatically increased. This occlusive effect must be accounted for when extrapolating toxicology studies conducted under occlusive conditions to field scenarios where the ambient environmental conditions are present. Hydration may also markedly affect the pH of the skin, which varies between 4.2 and 7.3. Therefore, dose alone is often not a sufficient metric to describe topical doses when the method of application and surface area become controlling factors. Dose must be expressed as mg/cm2 of exposed skin. 

Transdermal patches are marketed worldwide with the drug substances glycerole trinitrate, estradiol, testosterone, clonidine, scopolamine, fentanyl and nicotine, respectively. The patch has to remain for up to one week at the appropiate body site. In this case the drug amount in the reservoir is rather high. As liquid crystalline vehicles with lamellar microstructure have... 

Petrolatum-mineral oil ointment is retained longer on the eye than other vehicles. The large molecules of the petrolatum-mineral oil-base ointment are not easily removed by blinking, and a component of the comeal tear film is a non-polar oil. Ointments are oil bases and non-polar, which is why they are readily absorbed by the pre-corneal and conjunctival tear films. To maintain dmg contact with the eye, patching is recommended (1). 

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