The Black-Scholes equation is applied in pharmaceutical engineering. The Black-Scholes equation is a classic equation in computational finance. In this work certain case of a modified Black-Scholes equation is analytically solved in the context of a problem of absorption of a drug by a tissue. The analytical solution is obtained using computer algebra specifically Maple. The solution is written as one series of associated Laguerre polynomials. In the procedure the Kummer M functions are used. The analytical solution is numerically tested and using experimental data is possible to estimate the pharmacological parameters of the tissue. We claim that our analytical solution will have important applications in pharmaceutical engineering.