Question

A patch has been designed to release a drug to treat airsickness. The patch is applied an hour before the flight and is worn until the flight is over. The patch is a cylindrical disk 3-mm thick with a radius of 1 cm. The drug is initially at a concentration of 50 mM. Assume that the concentration in the adjacent skin is much less than the concentration in the patch. The diffusion coefficient of the drug in the patch is 1 x 10-8 cm2/ s. The manufacturer must have the release rate above 0.5 x 10-10 mol/s to ensure that there is enough drug in the bloodstream for the drug to be effective. Using the data given, assess whether the desired release rate can be achieved for a 14-hour flight from San Francisco to Beijing. (Hint: Determine whether the semi-infinite medium approximation is valid.) If the criterion is not met, suggest possible ways to produce a higher flux.

Answer 1