Methods for transdermal drug administration

Adhesive transdermal drug delivery devices may be removed and subsequently reapplied to an area of skin if the adhesive has an initial adhesive/skin bond strength sufficient to maintain said transdermal drug delivery device on the skin to which it is applied for the entire predetermined administration period; and an adhesive/skin bond strength upon replacement on the skin after removal therefrom which is adequate to retain the device on the skin for the balance of the administration period.

EXAMPLE 1 Testoderm® TTS transdermal delivery systems for the administration of testosterone over 24 hours through non-scrotal skin were made as follows. A reservoir gel comprising 26 wt % testosterone, 1-2 wt % hydroxypropyl cellulose, and the remainder 95% ethanol was prepared by mixing testosterone, 95% ethanol and adding hydroxypropyl cellulose with mixing. The testosterone gel loading was 21 mg/cm 2 . A PIB adhesive composition was made by mixing HMW PIB (MW 1200000), LMW PIB (MW 35000) and light mineral oil in a weight ratio of 1:1.25:2. A 50 micron thick layer of the PIB adhesive was cast onto a 75 micron thick film of siliconized polyethylene terephthalate release liner. The adhesive side of the resulting two layer subassembly was laminated to a 50 micron thick film of EVA (9% VA). The gelled testosterone-ethanol mixture was placed on the EVA membrane. A backing member comprised of aluminized polyethylene terephthalate with an EVA heat sealable coating was laid over the gels and heat-sealed to the EVA copolymer using a rotary heat seal machine. Finished systems were punched from laminate using a circular punch and placed in sealed pouches to prevent loss of volatile components. The device has been applied to non-scrotal skin of patients and thereafter removed and replaced without measurable decrease in adhesive/skin bond strength, such that the device remained on non-scrotal skin for the balance of the 24 hour administration period. 
 EXAMPLE II A test sample of the PIB adhesive of Example I was obtained by removing the release liner and separating the EVA/PIB adhesive laminates from the backing member leaving a film of PIB adhesive on the EVA membrane. A silicone adhesive test sample was prepared by forming a film of H7-2292 amine resistant silicone adhesive available from Dow Corning on another 50 micron thick film of EVA (9% vinyl acetate). Each EVA/adhesive strip was applied to the forearm of a subject. After a 20 minute dwell period, the strips were removed using an Instron machine to measure the force of removal. The force was approximately 95 gm/cm for the PIB adhesive and 195 gm/cm for the silicone adhesive. The strips were reapplied to the forearm of the subject. The silicone adhesive did not readhere to the subject while to PIB adhesive had approximately the same peel force upon subsequent removal (105 gm/cm). There was no evidence of delamination of the adhesive layer or contamination of the adhesive surface with the PIB adhesive sample whereas the adhesive properties of the silicone adhesive were essentially destroyed. The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be affected within the scope and spirit of the invention.