Viagra effect on hypertensive patients
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).
