. Author manuscript; available in PMC: 2016 Dec 10.

Published in final edited form as: J Control Release. 2015 Sep 28;219:644–651. doi: 10.1016/j.jconrel.2015.09.052

Table 4.

Some mathematical models describing drug release mechanisms of TDDS [53].

TDDS

Release Mechanism

Function

Passive transdermal patches

Fick s law of diffusion

J = \frac{D K}{h} (C_{v} - C_{b})

Iontophoretic systems

Iontophoretic transport

J_{Δ ψ} = ε {- (D \frac{d C}{d X}) \pm v C}

J: the flux of a drug through the skin; D: the diffusion coefficient of the drug through the skin; K: the partition coefficient; h: the thickness of the skin; C_v: the drug solubility in the vehicle; C_b: the plasma concentration; ψ: the electric potential in the membrane; x: the position in the membrane; ε: the combined porosity and tortuosity factor of the membrane; v: the average velocity of the convective flow.