Pharmaceutical Manufacturing Handbook: Production and

Drug
plasma
concentration
FIGURE 1
Steady-state levels of transdermal dose
Minimum toxic
concentration
Minimum therapeutic
concentration
0 10 20 30 40
Time (h)
Steady - state drug levels achieved by transdermal delivery.
TABLE 2 Advantages of Transdermal Drug Delivery
Excellent for drugs with short half - lives
Analogous to IV infusion
Route bypasses fi rst - pass metabolism
Reduced side effects
Decreased dosing
Zero - order kinetics
Self - administration
Increased patient compliance
TABLE 3 Disadvantages of Transdermal Drug Delivery
Allergies to adhesives
Product of local irritation
Potential for abuse or misuse
Temperature affects delivery
Drug needs to be potent and have desired physical and
chemical properties
INTRODUCTION 795
Another historical perspective on transdermal drug delivery involved tobacco
farmers receiving transdermal doses of nicotine from handling tobacco leaves. A
paper published by Gehlback et al. in 1974 introduced the concept of transdermal
nicotine [5] . It was common for farm workers who had direct contact with tobacco
plants during rainy and humid conditions to exhibit symptoms often associated with
nicotine poisoning. This condition is called green tobacco sickness and has affected
many farm workers, particularly in states such as Kentucky and North Carolina,
where the farming of tobacco is signifi cant. Moisture on tobacco leaves from rain
or dew may contain signifi cant amounts of nicotine due to its high water solubility.
Farm workers directly handling tobacco leaves often retained the moisture -