Does sildenafil (Viagra) cause hypotension?

From the Guidelines

Sildenafil can cause low blood pressure, particularly when used concomitantly with nitrate medications, due to its mechanism of action as a phosphodiesterase type 5 inhibitor, which can lead to severe hypotension 1. When considering the use of sildenafil, it is crucial to understand its potential effects on blood pressure. This medication works by relaxing blood vessels, which can lead to a decrease in blood pressure. While this effect is generally modest in healthy individuals, it can be significant in those taking other blood pressure-lowering medications.

Key Considerations

• The combination of sildenafil with nitrates is contraindicated due to the risk of severe hypotension 1.
• Patients on sildenafil or similar medications should avoid taking nitroglycerine for at least 24 hours to minimize the risk of low blood pressure 1.
• The decision to use phosphodiesterase type 5 inhibitors in patients on long-acting nitrate therapy should be guided by the need for continued nitrate therapy versus alternative options, emphasizing the importance of careful clinical judgment 1.

Clinical Implications

The potential for sildenafil to cause low blood pressure underscores the need for cautious use, especially in individuals with pre-existing cardiovascular conditions. Symptoms of low blood pressure, such as dizziness, lightheadedness, fainting, and headaches, should be monitored closely. The risk of hypotension increases with higher doses of sildenafil and is most pronounced within 1-2 hours after administration, when blood levels of the drug are at their peak.

Guidance for Practice

Given the potential risks, patients should be thoroughly evaluated before starting sildenafil, and their use of other medications, particularly nitrates, should be carefully managed to avoid dangerous interactions. The guidance from the 2023 AHA/ACC/ACCP/ASPC/NLA/PCNA Chronic Coronary Disease Guideline 1 emphasizes the importance of considering the half-lives of different phosphodiesterase type 5 inhibitors, such as sildenafil, vardenafil, and tadalafil, when making decisions about their use in conjunction with nitrate therapy.

From the FDA Drug Label

1. 2 Hypotension Sildenafil citrate has vasodilatory properties, resulting in mild and transient decreases in blood pressure. Before prescribing sildenafil tablets, carefully consider whether patients with certain underlying conditions could be adversely affected by such vasodilatory effects (e.g., patients on antihypertensive therapy or with resting hypotension [BP less than 90/50], fluid depletion, severe left ventricular outflow obstruction, or autonomic dysfunction). Monitor blood pressure when co-administering blood pressure lowering drugs with sildenafil citrate.

Sildenafil can cause low blood pressure due to its vasodilatory properties, resulting in mild and transient decreases in blood pressure 2.

• Patients with certain underlying conditions, such as those on antihypertensive therapy or with resting hypotension, may be adversely affected by these vasodilatory effects.
• Concomitant use of organic nitrates in any form is contraindicated due to the greater risk of hypotension 2.

From the Research

Sildenafil and Blood Pressure

• Sildenafil can cause a reduction in blood pressure, with a study showing that 100mg of sildenafil can reduce blood pressure by -3.7/-3.6 mm Hg in healthy patients 3.
• The reduction in blood pressure is more significant when sildenafil is combined with other medications, such as alpha(1)-blockers or nitrates, which can lead to orthostatic hypotension 3, 4.
• However, the overall safety of sildenafil is good, even in patients with a history of cardiovascular disease, and the risk of hypotension is generally low when used as directed 5, 6.

Interaction with Other Medications

• Sildenafil can interact with other medications, such as nitrates, which can lead to a profound decline in blood pressure and are contraindicated 3, 4, 7.
• The combination of sildenafil with alpha(1)-blockers, except tamsulosin, may also result in larger declines in blood pressure and cause orthostatic hypotension 3.
• Sildenafil can also interact with other medications metabolized in a similar way, such as erythromycin and HIV protease inhibitors 5.

Special Considerations

• Patients with cardiovascular diseases should be assessed and counselled regarding their fitness for sexual activity before taking sildenafil 7.
• Sildenafil is absolutely contraindicated in patients receiving treatment with long-acting nitrates for ischaemic heart disease 7.
• Patients who need sublingual short-acting nitrates infrequently should not be precluded from taking sildenafil, provided they are aware that sildenafil is not to be taken within 24 h of taking the nitrate 7.