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where the effect of the dosage regimen was studies, the conclusion was that once per day medication gave the best compliance. Luscher, in his studies with hypertensives, indicated that 6075% of the patients were well controlled, but one-third to one-fourth of the patients were noncompliant. He concluded that with the advent of potent antihypertensive drugs, noncompliance has become the most important limiting factor in the management of hypertension. Vandereychen [9] in his article Chronic Illness Behavior and Noncompliance with Treatment concluded that improving adherence to treatment regimen may produce as great an impact upon disability and health as the development of new biomedical assessment and treatment techniques and may result in greater cost effectiveness of health care services. |
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Examples of novel systems that have made major impact in the patient compliance area include the Norplant birth control system and the Catapres TTS-Transdermal Therapeutic system. The Norplant birth control system is an implant containing the progestin levonogestrel and is effective for continuous reversible contraceptive protection for up to five years [10]. Norplant is composed of six dimethylsiloxane/methylvinylsiloxane copolymer capsules, 2.4 mm in diameter and 34 mm in length, each containing 36 mgs of levonogestrel. The capsules are implanted in a superficial plane beneath the skin of the upper arm and they should be removed by the end of the fifth year. The system releases 85 mg/day of drug initially, which declines to as low as 30 mg/day during its useful life. Blood plasma concentrations of 0.30 nanograms/mL over five years were observed in clinical trials [11]. The typical failure rate of the system in the first year is 0.2% compared to 3% with oral contraceptives, and second only to male sterilization in minimizing failure rate [12]. |
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Catapres TTS for the treatment of hypertension is a transdermal system with each patch providing continuous systemic delivery of clonidine for seven days at an approximately constant rate. The drug clonidine is a potent antihypertensive agent that is delivered orally at 0.1 to 1.5 mg doses t.i.d. or b.i.d. Catapres TTS is a multilayered film 0.2 mm thick, with system areas of 3.5, 7.0, or 10.5 cm2 with the amount of drug released being 0.1, 0.2, and 0.3 mg clonidine per day. Proceeding from the visible surface towards the surface that is attached to the skin are four layers: (a) a backing layer of pigmented polyester film; (b) a drug reservoir of clonidine, mineral oil, polyisobutylene, and colloidal silicone dioxide; (c) a microporous polypropylene membrane that controls the rate of delivery of clonidine from the system to the skin surface; and (d) an adhesive formulation of clonidine, mineral oil, polyisobutylene and colloidal silicone dioxide. Prior to use, a protective peel strip of polyester that covers layer d is removed [13]. |
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In patients, one weekly application of the 0.1 mg/day system produces levels of clonidine in plasma that correspond to trough levels of an oral dose of 0.1 mg given twice daily, but the blood plasma levels for the Catapres TTS are |
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