Viagra Type Medications
some drugs may be used to treat erectile dysfunction
Managing erectile dysfunction (ED) requires a careful review of the patient’s risks and systematic attention to correcting them. Phosphodiesterase inhibitors (ex. Viagra, Levitra, Cialis) can be very effective in helping to manage ED and they work by causing smooth muscle relaxation in the blood vessel walls which results in vasodilation and enhanced/prolonged erection. They do this by maintaining blood levels of cGMP which is the mediator of endothelial produced Nitric Oxide (a very important vasodilating factor). Viagra was the first drug to be approved in 1998 and has the shortest half-life of 4 hours (its effect wears off the soonest of the three available drugs). Levitra was the 2nd drug to be approved in 2003, and compared with Viagra it is 5-10 times more potent, acts sooner, and has a similar half-life. Cialis is the 3rd agent approved in 2003 and has the longest half-life of 18 hours. In patients who have heart disease, there may be some risks to using these drugs, and so arguably, for patients in whom the drug is considered safe to use, the drug with the shortest half-life (Viagra) may be the safest.
Side effects with these drugs are typically minor and include flushing, headache, nasal congestion, gastric reflux, visual changes, muscle cramps, and a reduced blood pressure.
Some patients may experience a significant drop of blood pressure (BP) and this is especially likely to occur in those men who are taking nitrates. Other types of patients at risk include those with active ischemia, congestive heart failure, those who are on multiple antihypertensives, or have a tendency to low blood pressure.
Viagra acts quickly peaking within 30-120minutes. It is metabolized in the liver by an enzyme (cytochrome P450 3A4 and to a lesser extent P450 2C9) whose activity can be affected by many other drugs. It is important for the pharmacist and doctor to be aware of any other meds that the patient may be taking which might affect these enzymes in the liver. For example, certain antibiotics, heart , diabetes, antacid and seizure pills, , steroids, as well as certain herbs ( ex. St John’s wort) and even grape fruit juice represent types of agents which may either increase or decrease circulating levels of Viagra through their influence on the above liver enzyme, thereby making the patient more or less responsive to the drug’s effects.
Patients at risk with Viagra include:
- Older patients >65yrs *
Liver disease (cirrhosis) *
Significant Kidney disease (creatinine clearance <30 m/min) *
Patients taking Drugs that may inhibit the liver’s metabolism of Viagra *
(cytochrome P450 3A4, or 2C9) and produce higher circulating blood levels
Nitroglycerin use (see below)
Patients with significant ischemia on stress testing
Multiple Blood Pressure drugs
Congestive heart failure
Tendency to Low Blood Pressure
* these patients may be at risk for elevated levels of viagra *
The American Heart Association (AHA) 1999 consensus guidelines recommend against prescribing Viagra to patients taking “any form of nitrate therapy” within the past 24 hours. The reason for this is that any recent need for nitrates may be a sign that additional nitrates may be needed in the very near future. Also, these guidelines caution against using nitrates in any patient who may have taken a Viagra within the past 24hours. The rational for this is based on the fact that blood levels of Viagra will drop by approximately 50% after the passage of 4hours (half-life). So, by the time 24 hours has elapsed post-use of viagra, the amount of residual circulating Viagra should be extremely low. However, in some patients at risk (see above*) the liver metabolism of Viagra may be slowed, and its blood level may hang-around longer than usual. In this case, a longer period of time than 24hours may be needed before considering any administration of nitroglycerin to be safe.
Erectile dysfunction (ED) is common in men with coronary artery disease. This is partly due to the fear of triggering an event, the presence of vascular disease, side effects of certain cardiac medications, androgen deficiency, etc. Some of these patients may respond to certain performance enhancing medications (ex. Viagra has the shortest half life of those available).
Prior to considering the use of Viagra in any patient, and during a review of a patient’s sexual history, it is important to identify whether or not coronary artery disease is present, and if so, then to what extent it is, and whether or not the patient may be in need of anti-anginal therapy.
Overall, If a patient has stable coronary artery disease, does not have significant ischemia on stress testing, and does not require the usage of nitrates, then Viagra use may be considered after a review of the risks/benefits of doing so. Generally, a patient who is able to exercise to 6METs on a stress test without provoking ischemia, is thought to be safe for routine sexual activity, especially if the patient is regularly sexually active, is in good condition, and no “surprises” are introduced into the sexual activity that might unexpectedly increase the patient’s level of stress. In addition, there is always some value in starting with a lower dose of Viagra in cardiac patients, since it may prove effective.
Two interesting observations relate to the use of dietary supplements and to an anesthetic agent that is commonly used in dental offices. L-arginine is a precursor to Nitric Oxide, but, it does not appear to present a risk to patient taking Viagra since its intake does not increase circulating levels of Nitric Oxide. Therefore, it is safe to take. Nitrous oxide (an anesthetic agent ) does not appear to convert to Nitric Oxide in the body, and does not appear to affect levels of cGMP. Therefore, it doesn’t appear to present a risk to patients taking Viagra.
How can you tell if it is safe for a heart patient?
Overall, clinical evidence suggests that certain cardiac patients may safely engage in sexual activity provided that common sense is exercised .
Sex is an exercise and its energy expenditure can be measured in a definable manner. Studies have demonstrated that sex may cause heart ischemia (both the symptomatic kind, as well as the silent kind). Studies have also shown the ability to reduce these activity related symptoms by using anti-anginal medication.
The energy demand of sex may vary amongst individuals and may be measured as a metabolic equivalent (METs). Previous investigation has demonstrated a broad variability for “man on top activity “ ranging from 2.0-5.4 METs. The same study showed lower average energy expenditure for “woman on top” activity compared with “man on top” activity (2.5 vs 3.3) and a lower average peak heart rates with “woman on top” activity (110bpm) compared with “man on top” activity (127bpm). The reason that this information is useful to know, is because exercise tests provide the cardiologist with a sense as to what level of METs a patient may safely achieve while running on the treadmill in the doctor’s office. If a patient can safely run for 10METs on the treadmill without experiencing any ischemia, then the odds are good that he will be able to have sex without experiencing any ischemia. As a result of studies such as this, American Heart Association (AHA) guidelines suggest that a patient who can achieve 6METs of activity without provoking ischemia is not likely at an increased risk of developing ischemia during “normal sexual activity.
The exercise stress test can provide a sense of a patient’s exercise tolerance and whether or not he is at risk to develop ischemia and, if so, then at what workload it presents itself (ie. how quickly does it get triggered). Additional useful information includes the ability to ensure that the blood pressure response to exercise is appropriate, and that there is no evidence of any unexpected arrhythmias. In the case of stress echo studies, in addition to allowing for a more qualitative assessment of underlying ischemia, the cardiologist can also assess the response of any valvular heart disease or pulmonary hypertension to the exercise.
Exercise testing is always done in a standardized fashion,with sequential stages each having unique speeds (mph) and inclines (%grade) that are reproducible amongst all cardiologists. Depending on how well a patient does on the exercise test, the cardiologist can demonstrate the amounts of METs that a patient can safely achieve while in the office, allowing the patient to derive some comfort in knowing that he may not necessarily be at increased risk for activity related ischemia later on at home.
Fortunately, death during sex has rarely been reported.
Erectile dysfunction (ED)
Normal male sexual function requires a balanced interaction between healthy vascular , neural, endocrine, and psychological systems. Erectile dysfunction (ED) is defined as the recurrent inability to acquire or sustain an erection of sufficient rigidity and duration for sexual intercourse. ED is extremely common, first emerging as a problem for some men in their 40’s, and becoming more prevalent in later years.
A healthy erection requires an increased and sustained blood flow to be present and for this to occur, the blood vessels need to be healthy. Specifically, the inner lining of the blood vessels (endothelium) needs to function properly in order to maintain good blood flow, because it is here that determines whether a vessel will be constricted (reduced blood flow) or dilated (increased blood flow) as needed under different clinical circumstances. In general, the ability to increase the blood flow to an organ is very important, because it is this blood flow that allows for various good “fuels” to be brought in and for waste “toxins” to be brought out.
There is a vast array of influences (inflammatory, antioxidant, immunologic, hormonal, etc) which are constantly interacting at the level of the vascular endothelium with the intent to influence the vascular tone, the blood flow, and ultimately to create chronic permanent atherosclerotic changes in the blood vessel walls which we recognize as vascular disease.
These influences exert their effects by causing the endothelium to release either dilating (good) or constricting (bad) factors which in turn directly affect the flow through these blood vessels by directly acting on the adjacent smooth muscle layer that is present within the vessel walls. Nitric Oxide (NO) is recognized as one of the most potent naturally produced vasodilating factors around and also appears to be an antioxidant, antiplatelet, and anti-inflammatory factor. So, there are many benefits to having a healthy vascular system that is capable of producing Nitrous oxide whenever needed.
Long before atherosclerosis appears, the vascular endothelium becomes dysfunctional (as described above) and even at this early stage, it is clear that the ability of the blood vessel to vasodilate becomes impaired. This tends to be more prevalent in patients who are smokers, diabetic, hypertensive, dyslipidemic, overweight, older, or inactive. Further confounding this observation, is the fact that some heart medications that are commonly used to treat these very conditions may contribute to ED.
From a cardiology perspective, erectile dysfunction may be a sign of vascular endothelial dysfunction which in turn is considered to be an early sign of vascular atherosclerotic disease. For this reason, it is very important to consider a patient’s cardiovascular health when he presents with erectile dysfunction.