Pfizer Pharmaceuticals, the maker of Viagra, recommends that any patient who has taken Viagra within the past 24 hours NOT receive Nitroglycerin for a cardiac event!!! There have been cases where the patients has developed irreversabke hypotension and has expired!!!

Effective immediately, Dr. Mel Ochs (San Diego County Emergency Medical Director) wants all patients who have chest pain and are potential reciepiants of nitroglycerine to be screened for recent Vigra use prior to giving it. This includes women! If the patient has taken Viagra, NTG should not be given.

It will take time for us to fully research this issue, but if it turns out that thuis is the correct thing to do, we will modify the protocols as soon as we can to list VIGARA use as a STRICK CONTRAINDICATION to nitroglycerin administration if taken within the last 24 hours.

Viagra (sildenafil citrate) has a serious synergistic effect with nitrates. Viagra works by preventing the reduction of cyclic-Guanine Monophophate to plain old GMP. cGMP prevents the activation of protein kinases that cause smooth muscle to contract. In normal vascular tissue, cGMP levels are increased by increases in Nitric Oxide (NO). NO is released at the endothelial level of all vascular endothelium. Nitroglycerin and all nitrates release NO as their primary mechanism of action. Since Viagra's elimination half-life (t 1/2-beta --20 hours) is longer than it's distribution half-life (t 1/2- alpha --4 hours), any synergistic effect can last up to 28 hours from last ingestion. There is no information regarding the myocardial damage found in any of the deaths attributed to Viagra. I have heard reports that in at least one case there was no myocardial damage noted on post-mortem. The warning put out by on this list should be heeded, at least until we have substantial data. (6 cases still equal anecdotal episodes, not data).

Parallels Between Redux and Viagra

It's looking a little like deja vu all over again for the pharmaceutical industry!

Some bad news about Viagra is emerging: it may be dangerous to use Viagra with certain other drugs; we've even heard reports of deaths associated with Viagra being investigated by the FDA. Will Viagra suffer the same fate as Redux and be forced off the market?

You no doubt recall that FDA took Redux off the market after reports that long-term use caused heart valve problems (see, for example, FDA ANNOUNCES WITHDRAWAL OF FENFLURAMINE AND DEXFENFLURAMINE. Now there are concerns that Viagra, when used with recreational nitrates (including amyl nitrate/nitrite or "poppers" and others) may cause "a precipitous drop in blood pressure [that] could range from no symptoms or mild symptoms of hypotension such as dizziness or light-headedness, to syncope (most likely postural), to a significant lowering of coronary perfusion and conversion of an area of myocardial ischemia to infarction, with all of its potential consequences." (See Dear Doctor: Concomitant Administration of Viagra and Organic Nitrates).

Why haven't these problems been seen before? As with any new drug, the fact is that not all combinations of drugs have been tested with Viagra. Also, problems that were not seen in relatively small-scale clinical trials may surface only when millions of people begin taking drugs under uncontrolled situations. That is why it is extremely important that new drugs be used with caution and only under a doctor's supervision. Viagra could be a very significant help to patients that really require it for the approved indication (erectile dysfunction) and when used with the proper caution. We believe that Pfizer is acting prudently to prevent the misuse and to stop inappropriate prescribing situations -- such as prescribing Viagra to patients over the phone without knowing their full medical history. Take a lesson from Redux. It now appears that short-term use of Redux -- the way it was intended to be used -- may not lead to heart valve problems afterall (see Short-term Dexfenfluramine Therapy Not Associated with Heart-valve Damage! Nevertheless, Redux will never be re-introduced to the market. Viagra could suffer the same fate if it is continued to be prescribed and used inappropriately.

John Mackwebmaster, PharmInfoNet

More info here: Date of update: 5/25/98

Concomitant Administration of Viagra and Organic Nitrates (Medwatch)
In this Dear Doctor letter, Pfizer Inc. notifies health professionals -- especially emergency physicians -- of concomitant administration of Viagra and organic nitrates.

Sildenafil for Erectile Dysfunction (MSB)
Sildenafil (Viagra) recently has been approved for the treatment of erectile dysfunction in men. This article explains how it works, provides clinical tips, and points out the dangers of concomitant use with certain other drugs.

Viagra Meets 'Ultimate Goal' For Erectile Dysfunction Treatment (DrugPR) Pfizer Inc's Viagra (sildenafil citrate) is the only approved herapy that meets America Urological Association treatment standards for erectile dysfunction, according to the results of two major clinical trials summarized in this press release.

Viagra (Sildenafil) Appropriate Use Guidelines Reiterated (DrugPR)
In this press release Pfizer Inc reiterated guidelines for the appropriate use of Viagra (sildenafil citrate), its oral medication for the treatment of erectile dysfunction (ED) now available in the United States by prescription.

John Mack webmaster, PharmInfoNet

For info about Viagra, CONTACT:

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