Nifedipine usually is used against high blood pressure.
Also nifedipine cream is used for treatment of anal fissures.
Can the topical cream applied anally also cause hypotension?
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1 Answer
Nifedipine is a dihydropyridine calcium channel blocker. As you point out, it is used via oral administration for treatment of hypertension. Its effects are mediated primarily by blocking voltage-dependent calcium channels in the walls of systemic vasculature, causing vasodilation. This has the effect of lowering blood pressure.
Your question, then, rests on whether the nifedipine applied topically to the anus will reach the calcium channels in the vasculature. This is: is topical nifedipine systemically absorbed to a clinically relevant extent?
The answer, based on the research I can find, is no. This was explored directly in a study1: Serum levels and possible haemodynamic effects following anorectal application of an ointment containing nifedipine and lignocaine : a study in healthy volunteers. The authors used 3 g of an ointment containing 0.3% w/w2 nifedipine, applied twice daily for 7 days. Serum levels of nifedipine were below the below the limits of quantification, consistent with therapeutically negligible concentrations. Mean blood pressure was not changed when compared to baseline.
Notes
1. Perrotti P1, Grumetto L, Barbato F, Antropoli C. Clin Drug Investig. 2006;26(8):459-67. Note: I was not able to locate a free full text version of this. All of the information reported in my answer is verifiable using the abstract at the link provided. If you would like more information about the specifics of methodology, please fell free to ask in comments or ping me in chat.
2. Weight/weight. If the concentration is significantly higher, the answer may be different.