The content below discusses two delivery methods for NRT, the equations associated with each model and questions for review.

Patch Delivery: Model as Two Semi-Infinite Walls

The model of two semi-infinite walls suggests that the patch starts (t=0) with a uniform mass density Phpi and the skin starts with an initial mass density of zero. As time increases, eq 1 shows the rate of mass flux at the interface, which is appropriate both from the patch to the skin. Eq 2 shows that there is a conservation of mass flux. An important constant is the partition coefficient which, as shown in eq 3, determines how much mass can move from the patch to the skin. The dosage of nicotine from the patch can be calculated from eq 4.

Study Questions

1. Either by finding the appropriate data or by good, justified assumptions, determine the dosage for a nicotine patch over the timeframe that it is typically applied.
2. Compare these numbers with the approximate concentration of nicotine from smoking. The most important results are the comparisons. For example, how would an increased or decreased Kp affect the results? What about Dns? What physiological reasons could affect these parameters?

Gum Delivery: Model as Arnold Diffusion Cell

The model of the Arnold cell of a drug concentration from the gum to an area on the inner lip can be modeled as follows: The molar flux of the nicotine into the bloodstream through the skin, which is resistant to flux. The thickness of the dermal layer in the mouth can be assumed to be 50 mm at the end of which the blood takes all of the dug away, xnL = 0. However, this dermal layer can be assumed to be 75% covered by pores which are essentially saliva filled (saliva has a similar concentration as water). Eq 1 gives the molar flux of nicotine down each pore, and eq 2 gives the total dosage over area can time.

Study Questions

1. Either by finding the appropriate data or by good, justified assumptions, determine the dosage for a piece nicotine gum over the timeframe that it is typically used.
2. Compare these numbers with the approximate concentration of nicotine from smoking. The most important results are the comparisons. For example, how would an increased or decreased Kg affect the results? What about Dns or L? What physiological reasons could affect these parameters?

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