Findings call for a reassessment of whether the contraindication is warranted
Robert A. Kloner, MD, PhD, chief science officer at the Huntington Medical Research Institutes in Pasadena, Calif., and professor of medicine at University of Southern California, Los Angeles, previously conducted research exploring drug interactions with PDE5 inhibitors, and in 2018, coauthored a literature review that concluded that PDE5 inhibitors and nitrates are contraindicated.
But now, considering these new findings, Dr. Kloner is offering a fresh perspective.
“This study is reassuring,” Dr. Kloner said in an interview. “I think that it’s time to reassess whether there should be an absolute contraindication, or this should be more of like a warning.”
He noted that in controlled studies, like the ones he previously conducted, PDE5 inhibitors and nitrates were administered “very close to each other, on purpose,” yet this probably doesn’t reflect typical practice, in which clinicians can guide usage based on durations of drug metabolism.
“I think that physicians might be more comfortable now prescribing the drugs at the same time, but then telling patients that they shouldn’t take the two drugs simultaneously; they should wait and take the nitrate 24 hours after the last Viagra, or the nitrate 48 hours after the last Cialis,” Dr. Kloner said. “I suspect that that is happening. I suspect also the fact that people would be more likely to take the nitrate in the morning and the PDE5 inhibitor at night probably also contributes to the safety findings.”
Dr. Kloner noted that blood pressures vary throughout the day based on circadian rhythm, and that the body can adapt to some fluctuations without negative effects.
There could still be some people who experience a drop in blood pressure and get sick from it from the two drugs interacting, but that’s probably not that common, he said.
The study was supported by several grants. The investigators disclosed relationships with Merck, BMS, Bayer, and others. Dr. Kloner consults for Sanofi.