[replacer_a] inhibits PDE-5, preventing it from breaking down cGMP. As a result, the levels of cGMP increase. Elevated cGMP levels contribute to the relaxation of smooth muscles in the penile blood vessels, facilitating increased blood flow to the penis during sexual stimulation.

The increased blood flow to the penis helps in the engorgement of the erectile tissues, leading to an erection. It's important to note that the medication does not induce an erection on its own; sexual arousal and stimulation are necessary for the drug to be effective.

It's essential to use this medication under the guidance of a healthcare professional and to be aware of potential interactions and side effects. Always follow the prescribed dosage and instructions provided by your healthcare provider.