Transdermal patches can be a very precise time released method of delivering a drug. Cutting a patch in half might affect the dose delivered. The release of the active component from a transdermal delivery system (patch) may be controlled by diffusion through the adhesive which covers the whole patch, by diffusion through a membrane which may only have adhesive on the patch rim or drug release may be controlled by release from a polymer matrix. Cutting a patch might cause rapid dehydration of the base of the medicine and affect the rate of diffusion.
The continued search for new and less toxic antifungals led to the discovery of the azoles several decades later with the first release in the early 1980s. However, in the 1990s, new discoveries of both fluconazole and itraconazole displayed a broader spectrum of antifungal activity. Eventually, these agents became subject to a number of clinically important limitations related to their development of resistance, the induction of hazardous drug interactions and their performance as they moved throughout the body and their toxicity. ( 17 )
There are also many drug interactions . Patients must read in detail the enclosed data sheet(s) of the medicine. For example, the azole antifungals such as ketoconazole or itraconazole can be both substrates and inhibitors of the P-glycoprotein , which (among other functions) excretes toxins and drugs into the intestines.  Azole antifungals also are both substrates and inhibitors of the cytochrome P450 family CYP3A4 ,  causing increased concentration when administering, for example, calcium channel blockers , immunosuppressants , chemotherapeutic drugs , benzodiazepines , tricyclic antidepressants , macrolides and SSRIs .