From the Guidelines
No, it is not safe to use low-dose tadalafil 5mg daily with Imdur (isosorbide mononitrate). These medications should never be taken together due to a potentially dangerous drug interaction. Both medications work by increasing nitric oxide levels in the body, which causes blood vessels to dilate. When taken together, they can cause a severe and potentially life-threatening drop in blood pressure (hypotension) [ 1 ]. This combination can lead to dizziness, fainting, heart attack, or stroke. The interaction occurs because tadalafil enhances the blood pressure-lowering effects of nitrates like Imdur.
According to the 2023 AHA/ACC/ACCP/ASPC/NLA/PCNA guideline for the management of patients with chronic coronary disease [ 1 ], phosphodiesterase type 5 inhibitors should not be used concomitantly with nitrate medications, often used to treat CCD, because of the potential for severe hypotension. Tadalafil is long-acting and has a half-life of 17.5 hours, and patients on tadalafil should avoid taking nitroglycerine for at least 48 hours.
Some key points to consider:
- Phosphodiesterase type 5 inhibitors, such as tadalafil, should not be used with nitrate medications [ 1 ].
- The use of phosphodiesterase type 5 inhibitors in patients on long-acting nitrate therapy should be guided by the need for continued nitrate therapy versus other alternative options available to the treating clinician [ 1 ].
- If you are currently taking Imdur or any nitrate medication, you should not take tadalafil or other phosphodiesterase inhibitors (like sildenafil or vardenafil) [ 1 ].
Always inform your healthcare provider about all medications you are taking to avoid dangerous drug interactions like this one.
From the FDA Drug Label
The primary efficacy and safety study conducted outside the US included 268 patients, with a mean age of 56 years (range 21 to 78 years). The population was 86% White, 3% Black, 0. 4% Hispanic, and 10% of other ethnicities, and included patients with ED of various severities, etiologies (organic, psychogenic, mixed), and with multiple co-morbid conditions, including diabetes mellitus, hypertension, and other cardiovascular disease.
The FDA drug label does not answer the question.
From the Research
Safety of Low-Dose Tadalafil with Imdur
- The use of low-dose tadalafil (5mg daily) with Imdur (isosorbide mononitrate) is a concern due to potential interactions between phosphodiesterase inhibitors and nitric oxide donor drugs 2.
- A study on sildenafil citrate, another phosphodiesterase inhibitor, found that coadministration with isosorbide mononitrate produced significantly greater reductions in blood pressure than isosorbide mononitrate alone, leading to the recommendation that sildenafil should not be administered to patients taking nitrates 2.
- However, there is evidence that low-dose tadalafil may have beneficial effects on cardiovascular health, with one study finding that tadalafil exposure was associated with lower rates of major adverse cardiovascular events and mortality in men with erectile dysfunction 3.
- Low-dose long-term use of phosphodiesterase-5 inhibitors, including tadalafil, has been shown to have potential benefits in various medical implications, including cardiovascular disorders 4.
- A study comparing daily 5mg tadalafil with on-demand 20mg tadalafil in diabetic patients with erectile dysfunction found that both protocols improved erectile function, but daily use of 5mg tadalafil significantly improved the quality of ejaculation and lower urinary tract symptoms more than on-demand use of 20mg tadalafil 5.
- Another study found that long-term use of low-dose tadalafil (5mg once daily) combined with sildenafil (50mg as needed) was effective and safe for patients with erectile dysfunction, with significant improvements in erectile function and no difference in adverse events compared to tadalafil alone 6.
Considerations for Use
- While there is no direct evidence on the safety of using low-dose tadalafil with Imdur, the potential interaction between phosphodiesterase inhibitors and nitric oxide donor drugs should be considered 2.
- Patients taking Imdur should be closely monitored for changes in blood pressure and other cardiovascular effects if low-dose tadalafil is prescribed 2, 3.
- The benefits of low-dose tadalafil on cardiovascular health and erectile function should be weighed against the potential risks of interaction with Imdur 3, 4, 5, 6.