Transdermal patch administration

These include atropine, scopolamine (hyoscine), trihexyphenidyl (benzhexol) and benzatropine. They block central muscarinic receptors involved in various afferent pathways of the vomiting reflex (Fig. 1). They have been used to control motion sickness, emesis in Meniere s disease and postoperative vomiting. Currently, hyoscine is largely restricted to the treatment of motion sickness where it has a fast onset of action but a short duration (4-6 h). Administration of hyoscine by transdermal patch produces a prolonged, low-level release of the drug with minimal side effects. To control postoperative vomiting, it should be applied >8 h before emesis is anticipated. 

Non-oral forms of contraceptives, such as the transdermal patch and the transvaginal ring, avoid the need for daily administration and, as such, may enhance convenience of use for the patient. 

The answer is c. (Hardman, pp 543—544. Katzang, p 2533) Fentanyl is a chemical relative of meperidine that is nearly 100 times more potent than morphine. The duration of action, usually between 30 and 60 min after parenteral administration, is shorter than that of meperidine. Fentanyl citrate is only available for parenteral administration intramuscularly and intravenously. Tran sbuc cal ( lollipop ) and transdermal patches avoid first-pass metabolism of fentanyl. 

Rotigotine is available as a transdermal patch for once-daily administration, initiated at 2 mg/day and increased by 2 mg/day on a weekly basis to a maximum of 6 mg for early PD. 

This apparatus is primarily used for the transdermal patch. A variation of the apparatus is noted in a footnote in <724>. It is called the watchglass-patch-polytef mesh sandwich, and is favored by the US Food and Drug Administration (FDA) as the equipment of choice for transdermal patches. A diagram in Figure 16 illustrates how the system is assembled. 

The provision of optimal drug action from topical administration sites (such as ointments, creams, transdermal patches, ophthalmic, ear, and nasal preparations)... 

Transdermal and Topical Administration Transdermal administration is used to apply the drug on the skin surface. The drug is absorbed and transported by blood to receptors, which may be remote from the part of the skin where the transdermal patch is. The flrst pass metabohsm is circumvented. Topical administration is used to apply the drug for local effects. The typical areas for topical application are the skin, eyes, throat, nose, and vagina. 

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. 

Buprenorphine, the other option for transdermal application on account of its potency, is more difficult to apply dermally in therapeutic doses (Roy et al., 1994 Grond et al., 2000). A surrogate parameter for skin penetration, provided the other prerequisites are fulfilled (Fig. 7), is the melting point of the active substance. With buprenorphine base this is 209°C and about 260°C for buprenorphine hydrochloride, compared with, for example, 83°C for fentanyl base and 150°C for fentanyl dihydrogen citrate. The DDS developer LTS devised a technical solution for reliable transdermal buprenorphine administration in the form of a matrix patch (Fig. 9). 

Testosterone is available as oral testosterone undecano-ate, buccal testosterone, intramuscular testosterone esters, testosterone implants, and testosterone transdermal patches and gel. Proponents of transdermal testosterone products, such as gels and scrotal or non-scrotal dermal patches, claim that they have a good safety profile (101). Transdermal testosterone replacement certainly improves bone mass and lean body mass, reduces fat mass, and improves mood and sexual function. There are said to be no harmful effects on the prostate and lipids. Acne, polycythemia, and gynecomastia are stated to be less common with this form of therapy than with the intramuscular esters. To date these claims must be regarded with some reservations it is not at all clear that in equieffective doses the local or topical forms of administration dissociate wanted and unwanted effects. 

The development of the first transdermal patches in the 1980s generated considerable interest in this route of drug administration. Soon afterwards, iontophoresis was rediscovered and its potential to contribute to the new field of transdermal drug delivery was examined. This work provided the basic principles for modern iontophoretic devices [13,18-21]. Furthermore, and importantly, they demonstrated the existence of a (primarily) electroosmotic, convective solvent flux during transdermal iontophoresis [10,11,22-24], and it was shown that the permselective properties of the skin (a) could be exploited to enhance the transport of neutral, polar species and (b) have a clear impact on ionic transport. Subsequent research has better characterized skin permselectivity and the factors which determine the magnitude of electroosmosis [25-27],... 

Transdermal This route of administration achieves systemic effects by application of drugs to the skin, usually via a transdermal patch. The rate of absorption can vary markedly depending upon the physical characteristics of the skin at the site of application. This route is most often used for the sustained delivery of drugs, such as the antianginal drug, nitroglycerin (see p. 175). 

For sustained daytime angina prophylaxis, nitrates are of limited value because nitrate pauses of about 12 hours are appropriate if nitrate tolerance is to be avoided. If attacks occur during the day, ISDN, or its metabolite isosorbide mononitrate, may be given in the morning and at noon (e.g., ISDN 40 mg in extended-release capsules). Because of hepatic presystemic elimination, NTG is not suitable for oral administration. Continuous delivery via a transdermal patch would also not seem advisable because of the potential development of tolerance. With molsidomine, there is less risk of a nitrate tolerance however, its clinical use is restricted owing to its potential carcinogenicity. 

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