Dosage transdermal systems

For initial therapy, start with the 0.1 mg system. If, after 1 or 2 weeks, desired blood pressure reduction is not achieved, add another 0.1 mg system or use a larger system. Dosage greater than two 0.3 mg systems usually does not improve efficacy. Note that the antihypertensive effect of the system may not commence until 2 to 3 days after application. Therefore, when substituting the transdermal system in patients on prior antihypertensive therapy, a gradual reduction of prior drug dosage is advised. Previous antihypertensive treatment may have to be continued, particularly in patients with severe hypertension. 

Nicotine (transdermal system), dosage varies consult Nicoderm CQ, various generic ... 

The higher viscosity of semisolid dosage forms and transdermal systems may cause the rate of migration of leachable substances into these dosage forms to be slower than for aqueous solutions. Due to extended contact, the amount of leach-ables in these drug products may depend more on a leachable material s affinity for the liquid/semisolid phase than on the rate of migration. 

Povidone is capable of chemically stabilizing certain active ingredients. This effect does not depend on the dosage form, as povidone is used to stabilize nitroglycerin and isosorbide dinitrate, particularly in transdermal systems [384-386],... 

The selection of a vehicle can dramatically affect delivery and consequently efficacy of topical preparations. In terms of transdermal delivery, where delivering therapeutic agents for systemic effects is desired, solvents and co-solvent systems are widely used to improve both the amount and range of drugs that can be administered at therapeutic levels through the skin. Vehicles used in transdermal systems, such as patches, have recently been reviewed (Williams, 2003). In contrast, the focus of this chapter is on the use of solvents in topical dosage forms, i.e. preparations intended for a local or regional effect on the skin. 

Given the complexity of some of the dosage forms mentioned earlier, this guidance was limited to solid oral dosage forms, liquid oral dosage forms, and parenterals (small and large volume). These products serve as models, and the principles applied can be used for all other dosage forms such as inhalation products, topical formulations, and transdermal systems. 

The oxybutynin transdermal system (Oxytrol), which delivers 3.9 mg per day, is applied twice weekly (every 3 or 4 days). Transdermal absorption of oxybutynin from this formulation bypasses first-pass hepatic and gut metabolism, resulting in similar oxybutynin bnt lower plasma A-desethyloxybutynin concentrations than after administration of an equivalent dose via the oral route. ° Similar findings have been noted for the active i -enantiomer of Af-desethyloxybntynin. No dosage adjustment of the TDS product for advancing age is necessary. ... 

Fentanyl transdermal system is intended for transdermal use only. Doses should be individualized and calculated based on the PO, IM, or IV opioid requirements (see below, as pubhshed by the manufacturer). Available patch dosages are 12.5,25,50, 75, and 100 pg per hour. The 25 pg/h FTS patches were recalled in February2008 due to a concern that small cuts in the gel reservoir could result in accidental exposure to fentan)d [1]. 

This new dosage form recently was introduced to the pharmaceutical industry. Transdermal preparations now are commercially available for the alleviation of the symptoms of motion sickness (scopolamine), to provide symptomatic relief of angina pectoris (nitroglycerin), and for replacement estrogen therapy (estradiol), Transdermal systems offer advantages commonly associated with con-... 

Another technology that we have advanced for systemic treatment is the transdermal therapeutic system (TTS) for release of drug through intact skin into the circulation. The transdermal delivery system represents a major breakthrough. Previously we really had only two approaches to giving medication systemically tablets, which go back to the Egyptians, and injectable dosage forms, invented about a century ago. The transdermal system is potentially far superior to both. 

The European Pharmacopoeia (Ph. Eur.) has also adopted some of the apparatus designs (12) described in the USP, with some minor modifications in the specifications. Small but persistent differences between the two have their origin in the fact that the American metal processing industry, unlike the European, uses the imperial rather than the metric system. In the European Pharmacopeia, official dissolution testing apparatus for special dosage forms (medicated chewing gum, transdermal patches) have also been incorporated (Table 2 provides an overview of apparatus in Ph. Eur.). 

Dissolution testing has become an important component of the assessment of the quality of solid oral dosage forms and oral suspensions. The basic procedures for these oral dosage forms have been extended to transdermal delivery systems as well. The release rate for modified-release oral dosage forms adds a level of sophistication to the concept of dissolution testing, setting acceptance criteria at multiple time points. 

Various dissolution test systems have been developed and several of them now enjoy compendial status in pharmacopeias, for example the reciprocating cylinder (United States Pharmacopeia Apparatus 3), the flow-through apparatus [European Pharmacopoeia (Pharm. Eur.) 2.9.3], or the apparatus for transdermal delivery systems, such as the paddle over disc. Hydrodynamic properties of these and other apparatus have been described only sparingly. The paucity of quantitative data related to hydrodynamics of pharmacopeial dissolution testers is lamentable, since well-controllable hydrodynamics are essential to both biopharmaceutical simulations and quality control. Here, we focus the discussion on the paddle and the basket apparatus, since these are the most important and widely used for oral solid dosage forms. A brief treatise on the hydrodynamics of the flow-through apparatus completes this section. 

Topical delivery systems are self-contained, discrete dosage forms that are designed to deliver drug via intact skin or body surface. There are three types of topical delivery systems transdermal, ocular, and intrauterine. 

Dosages and routes of administration For acute (postoperative) pain and for anesthesia, fentanyl is given by the intravenous route. For pre-medication in anesthesia and for break-through pain the compound can also been given as an oral-transmucosal formulation (Ashburn and Streisand, 1994). A transdermal patch has been developed for chronic pain treatment (Jeal and Benfield, 1997 O Siordin, 1998). The intravenous doses for premedication are 50-100 pg, oral-transmucosal systems contain 200-400 pg and patch formulations have a delivery rate of 25-100 pg/h. 

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