Transdermal drug delivery disadvantages

Describe the advantages and disadvantages of transdermal drug delivery over other routes of drag delivery. 

Transdermal delivery is suitable for small, generally lipophilic, potent molecules that require low input rates to achieve effective plasma concentrations. There may be a slow rate of increase of concentration if the drug forms a depot in the skin. Depot formation will also result in a slow decrease in concentration when the system is removed from the skin. These disadvantages can be overcome by the use of iontophoresis, by which the molecules are actively carried across the skin by a small electrical current. This provides a faster and more controllable transfer of drug. Intramuscular/Subcutaneous... 

The disadvantages of transdermal patches are patient allergies to adhesives found in transdermal patches, patch excipients that sometimes produce local irritation, potential for abuse or misuse, temperature that can affect the delivery of drugs from certain patches, and the inability of most drugs to be delivered transdermally (Table 3) [2],... 

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