Contact type dispensing

A wide variety and numerous suppliers of automated dispensing equipment are available as listed in Table 4.22. An important consideration in selecting an automated, contact-type dispensing system is the pump used in the system, of which there are three types time-pressure, auger, and linear piston or positive displacement. " ... 

In general, methacrylate polymers are considered nontoxic. In fact, various methacrylate polymers are used in food packaging (qv) and handling, in dentures and dental fillings (see Dental materials), and as medicine dispensers and contact lenses. However, care must be exercised because additives or residual monomers present in various types of polymers can display toxicity. For example, some acryHc latex dispersions can be mild skin or eye kritants. This toxicity is usually ascribed to surfactants in the latex and not to the polymer itself. 

Most dispensers use spin-on type filters, similar in appearance and construction to most common engine oil filters. Most use steel housings and paper filter element that are compatible with ethanol, but the glue used to fasten the element to the housing may not be compatible with ethanol. The filter manufacturer should be contacted to see whether they have tested their filters for compatibility with ethanol (a recommendation without testing verification should be looked upon skeptically). If there is doubt, dispenser filters having nylon filter elements and ethanol-compatible glue should prove compatible. 

The five primary designs used for water distributors are orifice plate, trough-type distributor, orifice headers, combination of trough and orifices, and spray nozzles (see Fig. 2). These distributors equally dispense the water over the packing causing the water to break into tiny droplets, which increases the air-to-water contact. 

Rifampin s potent induction of hepatic enzymes, especially cytochrome P450 (CYP) 3A4, may enhance the ehmination of many other drugs, most notably the protease inhibitors used to treat HIV (Table 110-7). HIV-positive patients may beneht from the use of rifabutin instead of rifampin (see below). ° Also, women who use oral contraceptives must use another form of contraception during therapy because increased clearance of the hormones may lead to unexpected pregnancies. Patient records should be reviewed for potential drug interactions before dispensing rifampin. Rifampin may turn urine and other secretions orange-red and may permanently stain some types of contact lenses. 

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