Review Question - QID 100616

This patient may currently be taking a phosphodiesterase inhibitor (PDE-i) for his erectile dysfunction (ED). Nitrates (for chest pain) are contraindicated in patients using PDE-i's (for ED or pulmonary HTN) due to the risk for profound systemic hypotension.

Both nitrates and phosphodiesterase inhibitors have been found to share a pathway that leads to increased intracellular cGMP. This increase in cGMP leads to vascular smooth muscle relaxation, which in excess may lead to severe systemic hypotension. It is important to remember this relationship and to ensure patient safety even before dispensing samples of erectile dysfunction medication. For patients on PDE-i medications, alternative treatments can include beta blockers or calcium channel blockers for reduce of cardiac afterload.

Heidelbaugh discusses the management of ED. ED is often treated with phosphodiesterase 5 inhibitors. PDE-5-inhibitors should not be used in combination with nitrates because they lead to a synergistic effect. This can lead to serious, even fatal, hypotension.

Henderson et al. report on the co-possession of PDE-5-inhibitors with nitrates. They found that of 601,063 patients currently taking tadalafil, 3.31% were additionally prescribed a nitrate. Most of the co-possessed medications were found to be prescribed by different providers.

Illustration A is a diagram representing the mechanism of sildenafil, a phosphodiesterase-5 inhibitor used for ED. Illustration B depicts the mechanism of nitrates. Both classes of medication result in increased vascular smooth muscle relaxation.

Incorrect Answes:
Answers 1,3-5: Although it is important to know about each patient's medical problems and medications, only medications for erectile dysfunction would have a profound and potentially dangerous effect in combination with nitrates.