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Viagra And Blood Pressure Medications - The News Seems Good
A substantial number of men who take medications for high blood pressure (hypertension) have erectile dysfunction (ED). Erectile dysfunction is an inability to achieve or maintain a satisfactory erection. Certain diseases (including hypertension), medications (including some of those for blood pressure), or psychological factors can be the cause of the ED in these men. Many of my patients with hypertension ask me whether it is safe to take sildenafil (Viagra) with their blood pressure medications.

As you probably know, sildenafil is a relatively new, quite effective, and highly publicized treatment for ED. Yet, this question of safety is pertinent and logical since both sildenafil and many anti-hypertensive medications work by opening up or widening (dilating) certain blood vessels. Sildenafil dilates vessels to increase the blood flow to the penis, while the blood pressure medications dilate certain vessels to lower the blood pressure. Thus, the question arises as to whether it is safe to combine these two different medications (sildenafil and the various anti-hypertensives). Since they both independently dilate the blood vessels, it is conceivable that together they could lower the blood pressure too much.

How does sildenafil produce an erection? During normal sexual stimulation, a compound called nitrous oxide (NO) is released in the penis. The NO increases the level of a metabolic regulator known as cyclic GMP and, thereby, causes relaxation of the smooth muscle in the walls of blood vessels. As a consequence of this relaxation, the vessels dilate and blood flow into the shaft of the penis increases, thereby resulting in an erection. Sildenafil works by inhibiting the breakdown of the cyclic GMP so that the drug basically enhances the effect of the NO. Accordingly, in patients with ED, sildenafil dilates the blood vessels and increases the blood flow in the penis to produce an erection.

A mild dilating effect of sildenafil on blood vessels elsewhere in the body may lead to some flushing and/or headaches in some people. Furthermore, a decrease in systolic blood pressure (the top number of a blood pressure reading) of 8-10 mm Hg and diastolic blood pressure (the bottom number) of 3-6 mm Hg is not uncommon in healthy individuals using sildenafil. These changes in blood pressure occur within 1 hour and subside by 4 to 8 hours. Such a modest decrease in blood pressure, however, is generally well tolerated in normal individuals.

To answer the question as to whether sildenafil is safe to use together with anti-hypertensive medications, Kloner and colleagues analyzed the data from ten different, already published studies on the drug. In each of these studies, the subjects were given either placebo or sildenafil by chance (randomly) without the patients or the investigators knowing which was given (double-blind). It turned out that among the 3975 individuals taking sildenafil, 1094 of them were also taking one or more blood pressure medications. (Two hundred and seventeen patients were taking more than one blood pressure medication.) The anti-hypertensive drugs included diuretics, beta-blockers, alpha-blockers, ACE inhibitors, or calcium channel blockers, but not the newer agents, angiotensin receptor blockers.

The data from the 3975 patients were analyzed to compare the results of using sildenafil in the 1094 people who were taking anti-hypertensive medications to those in the 2881 people who were not. The investigators looked at the effectiveness of the drug in improving erections. In addition, they reviewed the side effects, particularly those (for example, dizziness and fainting) that might suggest an excessive lowering of blood pressure. Kloner and colleagues, for the Sildenafil Study Group, recently published the findings of this large but after-the-fact (retrospective) analysis in the American Journal of Hypertension (2001; 14: 70-73).

It is important to note that certain individuals were excluded from the original studies because using sidenafil and engaging in sexual activities might impose unwarranted risks on them. The excluded patients were as follows:

Those who had had a stroke, heart attack (myocardial infarction), or irregular heart beat (serious arrhythmia) within the previous 6 months.
Those who had low blood pressure (less than 90/50) or poorly controlled blood pressure (greater than 170/110).
Those who had a known history of retinitis pigmentosa, an eye disorder that might be aggravated in some patients by the sildenafil.
Those who were taking a nitrate (for example, nitroglycerin), which also dilates blood vessels, so that a marked decrease in blood pressure can occur when the sildenafil also is taken.
Those who were taking anticoagulants (blood thinners) because of the possibility that sildenafil also might impair blood clotting. (Whether this last precaution is necessary is uncertain.)
The results of the study were encouraging in that they revealed that approximately 70% of the patients on sildenafil reported improved erections, whether or not they were taking blood pressure medications. Furthermore, the frequency of adverse side effects from sildenafil was similar in individuals, whether or not they were taking blood pressure medications. The common side effects of sidenafil include headache, flushing, indigestion, and abnormal vision. In fact, one of these symptoms can occur in up to 1/3 of all patients using sildenafil. Most importantly, in relation to the safety question, however, the symptoms that would suggest an excessive drop in blood pressure occurred only rarely. What is more, these symptoms occurred in individuals with no difference in frequency, whether or not they were taking the blood pressure medications.

The authors concluded that sildenafil can be used safely with a variety of blood pressure medications without causing symptoms that would suggest an excessive lowering of the blood pressure. This conclusion seems valid, especially because the study included a large number of patients. The retrospective nature of this analysis, however, does somewhat limit the power of the findings. Furthermore, remember that the blood pressure was not actually measured in these studies before and after the sildenafil. Hence, minor and probably unimportant decreases in blood pressure, as described above for healthy people, could have also occurred in this study.

As a matter of fact, sildenafil works to dilate the blood vessels through a different process (as described above, involving the NO and cyclic AMP pathways) from that of the anti-hypertensive drugs. Perhaps this difference explains the lack of an additive or more than additive (synergistic) effect of these drugs on lowering the blood pressure. Still, sildenafil should be used with caution, if at all, in patients for whom lowering the blood pressure would pose a greater risk to their health. Such patients include those listed above who were excluded from the studies.

While a normal sex life is very important, the entire physical and emotional makeup of an individual must be considered in deciding whether to use sildenafil for ED. Thanks to basic science, with this drug, we now have the ability to treat ED in many patients. But, in some patients, it may be safer not to use sildenafil, as already discussed, and instead to try other remedies for ED.

Regarding sildenafil, this study should help clarify one area of concern for physicians and their patients who have both hypertension and ED. Thus, the drug seems to be safe to use along with the anti-hypertensive medications in patients with high blood pressure. Finally, although sildenafil (Viagra) can be obtained easily from a well-meaning friend or the Internet, a person should be sure to discuss the use of the drug with a physician before trying it.