Nifedipine diffusion

Julie Singer is a 55-year-old white woman who was admitted to the emergency department in acute distress. A previous physical examination showed hypertension and diabetes mellitus type 2. The patient s present medications include enalapril 40 mg, nifedipine 60 mg, and 100 U insulin. A physical examination revealed prominent ankle edema, a palpable spleen, and hepatomegaly. Chest radiography revealed diffuse cardiac enlargement and left ventricular hypertrophy. Based upon the history and clinical hndings, what is your diagnosis and what treatment do you recommend ... 

Various techniques have been applied in studies of solid samples. A direct method based on infrared spectroscopy has been used in the study of pharmacologically active compounds such as nitroimidazole derivatives (chemotherapeutics) and nifedipine (Marciniec and Rychcik, 1994 Marciniec et al., 1997). This approach can be applied in kinetic and quantitative examinations of the degradation process. An alternative method based on diffuse reflectance spectrophotometry takes into account the surface reflectance of the sample (Zhan et al., 1995). In recent years, Raman spectroscopy has become a powerful tool for the study of various processes in the solid state. The technique allows mapping of the concentration of one specific component within a sample, e.g., an active ingredient in a tablet formulation. This method may therefore become a useful tool in future studies of solid-state photodegradation (Opel and Venturini, 2002). 

While the experimental results are suggestive, simulation results are conclusive in their support for Lieb and Stein s hypothesis. Further, the simulations suggest refinement of their hypothesis. MD simulations of the passive diffusion within the bilayer of molecules of a range of sizes, including methane, benzene, adamantane, and nifedipine clearly show that small molecule (methane and benzene) movement includes discrete rapid jumps between voids within the bilayer. These voids are often as much as the volume of benzene, but seldom much larger. These jumps have been observed to be moderated by the torsional isomerization of the lipid hydrocarbon chains, whose motion creates passages between existing voids [4, 5,7,21]. These jumps are occasional for benzene, however they are very frequent for the much smaller molecule, methane. The movement of adamantane and nifedipine is... 

This provides a gradient across the bilayer to the rate of difiusion of the solutes. Diffusion is slowest close to the headgroups and becomes more rapid (by a factor of 4 for benzene) as the center is approached. The larger the solute, lesser is the gradient. It is very large for methane (a factor of 10 difference between the rates at various locations, a similar difference has been seen for water [22] but is nonexistent for the much larger nifedipine. 

Sun Y, Xi H, Ediger MD, Richert R, Yu L (2009) Diffusion-Controlled and Diffusionless Crystal Growth near the Glass Transition Temperature Relation between Liquid Dynamics and Growth Kinetics of Seven ROY Polymorphs. J Chem Phys, pp 131 Sun Y, Tao J et al (2010) Solubilities of crystalline drugs in polymers an improved analytical method and comparison of solubilities of indomethacin and nifedipine in PVP, PVP/VA, and PVAc. J Pharm Sci 99(9) 4023-4031... 

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