From the Guidelines
Sildenafil and diltiazem can be used together, but with caution, due to potential interactions that may increase the risk of hypotension. When taken concurrently, diltiazem, a moderate CYP3A4 inhibitor, can inhibit the metabolism of sildenafil, potentially increasing sildenafil blood levels and the risk of side effects such as hypotension (low blood pressure) 1. This interaction may necessitate using a lower dose of sildenafil (starting at 25mg rather than 50mg) when taken with diltiazem. Some key points to consider when using these medications together include:
- Monitoring patients for symptoms of hypotension, including dizziness, lightheadedness, or fainting, especially when initiating the combination 1
- The risk is particularly significant in elderly patients or those with underlying cardiovascular conditions
- If both medications are deemed necessary, patients should be advised to separate the timing of doses when possible and report any concerning symptoms to their healthcare provider immediately
- This combination is not absolutely contraindicated but requires careful management and monitoring, as stated in the guidelines for the management of adult patients with supraventricular tachycardia 1. It's also important to note that sildenafil is contraindicated with nitrates, and the use of nitrates within 24 hours after sildenafil or the administration of sildenafil in a patient who has received a nitrate within 24 hours has been associated with profound hypotension, MI, and even death 1. However, there is no direct contraindication between sildenafil and diltiazem, but caution is advised due to the potential for increased hypotension.
From the Research
Contraindications with Sildenafil and Diltiazem
- There are no direct studies comparing the contraindications of sildenafil and diltiazem together, however, it can be noted that:
- Sildenafil is contraindicated with nitrates and nitrate donors due to the risk of severe hypotension 2, 3, 4.
- Diltiazem is a calcium antagonist that can cause hypotension as one of its adverse events 5.
- Sildenafil is metabolized by cytochrome P450 enzyme CYP3A4, and its plasma concentrations can be increased by CYP3A4 inhibitors, which may increase the risk of side effects 2, 4.
- Diltiazem is also a CYP3A4 inhibitor, and its co-administration with sildenafil may increase sildenafil plasma concentrations, potentially leading to increased side effects 4, 5.
Potential Interactions
- The combination of sildenafil and diltiazem may increase the risk of hypotension due to the additive effects of both drugs on blood pressure 4, 5.
- Patients taking diltiazem and sildenafil together should be monitored for signs of hypotension, and dose adjustments may be necessary to minimize the risk of side effects 4.