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#MOTION SICKNESS PILLS SKIN#
When the drug is delivered faster than the skin can absorb it, the skin surface is then saturated with drug at all times, and the limiting factor for systematic dosage is the rate of absorption through the skin. If drug is delivered to the skin at less than the maximum rate at which it can be absorbed, the device is the primary dosage-controlling mechanism. The pattern of drug release from the device is important. These devices offer an important advantage over the monolithic geometry: as long as the drug solution in the reservoir remains saturated, the drug release rate through the membrane is constant. In this case, the drug-usually in liquid or gel form-is contained in a reservoir separated from the skin by an inert membrane that controls the rate at which drug is delivered to the skin. The third type of device is the reservoir system ( Fig. With this type of system, the drug release rate falls off with time as the drug in the skin-contacting side of the matrix is depleted. The matrix layer consists of a polymer material in which the solid drug is dispersed the rate at which the drug is released from the device is controlled by this polymer matrix. 9, middle) incorporating a backing layer, a matrix layer, and an adhesive layer. The second type of device is a monolithic system ( Fig. Nitroglycerin and nicotine are currently the most important drugs, but the area of hormone replacement therapy is growing as a result of improved estradiol and testosterone delivery patches. Despite the enormous interest in transdermal delivery in academia and industry, the number of drugs delivered transdermally is currently limited to nitroglycerin, nicotine, estradiol, clonidine, fentanyl, testosterone, and isorbide nitrate. Very active skin-permeable drugs are required to make transdermal drug delivery possible.
#MOTION SICKNESS PILLS PATCH#
Because the maximum acceptable size of a transdermal patch is limited to about 50 cm 2, drugs delivered through the skin must be effective at doses of 0.01 mg/day for a poorly skin-permeable drug and 10 mg/day for a highly skin-permeable drug. Depending on the drug, skin permeabilities are in the range 0.01–10 μg of drug/cm 2 The main problem limiting widespread use is the low permeability of most drugs through the skin. However, the number of drugs that can be delivered through the skin is more limited than was anticipated when the first patches were introduced in the 1980s. Since then the market for transdermal patches has grown steadily. Scopolamine, for control of motion sickness, was the first drug to be marketed in the form of a transdermal patch system. Baker, in Encyclopedia of Physical Science and Technology (Third Edition), 2003 III.B Transdermal Systems