Transdermal Topical Products

The manufacturing of topical transdermal products (patches) has many problems in scale-up and validation. Problems analogous to production of topical creams or ointments include uniformity of the drug substance and particle size in the bulk gel or ointment. Uniformity and particle size are particularly significant when the drug substance is suspended or partially suspended in the vehicle. Viscosity also needs control because it can affect the absorption of the drug the dissolution test is important in this regard. Other areas that need special inspectional 

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Oral or transdermal estrogen products should be prescribed at the lowest effective dose for the relief of vasomotor symptoms. Topical products in the form of creams, tablets, or rings should be prescribed for women exclusively experiencing vulvovaginal atrophy. 

There is a large literature on this subject, mainly concentrated in the field of oral products. Bioequivalence is, however, a potential problem with other routes of administration such as transdermal, topical and intramuscular... 

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. 

Topical products Examples exist for most animal species. Transdermal formulations that achieve... 

Non-sterile products, i.e. transdermal patches, vaginal-rectal products, local and topical products, liquid oral products, solid oral... 

Instructions for application of the topical ointment or transdermal system are available with the product. Read tiiese instructions carefully. 

We tend to think of them being much the same, but the functioning of semisolid dermatological products stands in stark contrast with that of transdermal delivery systems. To begin with, most topical applications... 

Transdermal Administration. The development of the stratum corneum is complete at birth and is considered to have permeability similar to that of adults, except in preterm infants [81], Preterm neonates and infants have an underdeveloped epidermal barrier and are subject to excessive absorption of potentially toxic ingredients from topically applied products. 

As pharmaceutical scientists gain experience and tackle the primary challenges of developing stable parenteral formulations of proteins, the horizons continue to expand and novel delivery systems and alternative routes of administration are being sought. The interest in protein drug delivery is reflected by the wealth of literature that covers this topic [150-154]. Typically, protein therapeutics are prepared as sterile products for parenteral administration, but in the past several years, there has been increased interest in pulmonary, oral, transdermal, and controlled-release injectable formulations and many advances have been made. Some of the more promising recent developments are summarized in this section. 

Typical patches of estradiol contain 50 micrograms, but there are important differences between the wanted and unwanted effects of the available products, because of the ways in which they are formulated. The wash-out period of estradiol after transdermal administration is about 6 weeks. Transdermal estrogens can also be supplemented periodically by an oral progestogen (222). New topical formulations of estrogens continue to be studied and... 

Topical and transbuccal systems. In the current literature, unfortunately, transdermal products usually are labeled for systemic use only. It is the time to define transdermal products for topical (excluding dermatological) use to those delivered through the intact and healthy skin directly into the local tissues or deeper regions beneath the skin. Dozens of these transdermal systems have been launched for topical use, including analgesics for muscle aches, neuropathic pain, and arthritis and the treatments of breast cancer and erectile dysfunction.88... 

Transdermal delivery of proteins and/or DNA vaccines for needle-free immunization has been attracting increasing interest. Cui et al. [110] reported on ethanol-in-fluorocarbone (E/F) MEs for topical immunisation. The authors showed that plasmid DNA incorporated into E/F MEs was found to be stable. Furthermore, after topical application to the skin, significant enhancements in luciferase expression, antibody production, and T-helper type 1 based immune response compared to an aqueous or ethanolic solutions of DNA were observed [110]. 

Pharmacia and Upjohn, Kalamazoo, MI) and Cri-none Gel (Wyeth-Ayerst). Mineral oil is frequently present in transdermal products such as Catapres-TTS (Boehringer Ingelheim) and Estraderm (Novartis Pharmaceuticals Corp). In addition, numerous ocular or topical ointments, such as TobraDex (Alcon Labs, Fort Worth, TX) and Nitro-Bid (Hoechst Marion Roussel, Kansas City, MO), use white petrolatum and mineral oil as a base. Short-chain triglycerides such as triacetin can be found in products such as Prepidil Gel (Pharmacia-Upjohn, Kalamazoo MI), a cervically administered prostaglandin. 

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