Hormonal Nifedipine

Rifampin is known to induce the hepatic microsomal enzymes that metabolize various drugs such as acetaminophen, oral anticoagulants, barbiturates, benzodiazepines, beta blockers, chloramphenicol, clofibrate, oral contraceptives, corticosteroids, cyclosporine, disopyramide, estrogens, hydantoins, mexiletine, quinidine, sulfones, sulfonylureas, theophyllines, tocainide, verapamil, digoxin, enalapril, morphine, nifedipine, ondansetron, progestins, protease inhibitors, buspirone, delavirdine, doxycycline, fluoroquinolones, losartan, macrolides, sulfonylureas, tacrolimus, thyroid hormones, TCAs, zolpidem, zidovudine, and ketoconazole. The therapeutic effects of these drugs may be decreased. 

This reaction produces symmetrical dihydropyridines whose chemistry can be traced back to the late 1800s, biochemistry shortly thereafter, and pharmacology relevant to the present indication to the early 1970s. ( though its precursor nifedipine suffered from too short a half-life, if anything, 20 may now have too long a half-life, and T3 ratios can vary in the natural hormone. 

Valentijn, K. et al., Omega-conotoxin- and nifedipine-insensitive voltage-operated calcium channels mediate K(-t)-induced release of pro-thyrotropin-releasing hormone-connecting peptides Ps4 and Ps5 from perifused rat hypothalamic slices. Brain Res Mol Brain Res 14, 221, 1992. 

Cadmium accumulation by MDCK cells also appears to be mediated in part by agonist-stimulated calcium channels (Flanagan and Friedman 1991). Parathyroid hormone, a stimulator of calcium uptake in MDCK cells, increased cadmium uptake. The dihydropyridine agonist BAY K8644 augmented the effect of parathyroid hormone, an effect that was competitively inhibited by the calcium channel antagonist nifedipine (Flanagan and Friedman 1991). 

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