• Characteristics of Transdermal Drug Delivery Systems (TDDS):
• Advantages: Completely bypasses hepatic first-pass metabolism, eliminates erratic gastrointestinal degradation, reduces peak-trough plasma fluctuations, and provides prolonged zero-order drug input with improved owner compliance.
• Pharmacokinetic Profile: TDDS produces slow, controlled, non-fluctuating plateau concentrations. It does NOT produce high peak plasma drug concentrations ($C_{max}$); rather, avoiding sharp spikes is one of its primary clinical advantages [Statement 4 is the exception].

Correct option: (4) They produce high peak plasma concentration of the drug