What are phosphodiesterase-5 inhibitors? Phosphodiesterase-5 inhibitors (PDE5 inhibitors) are drugs that improve blood flow to certain body tissues, including penile tissue. Although originally designed to treat cardiovascular conditions such as high blood pressure and angina pectoris, today they are the standard treatment for erectile dysfunction in men. How do phosphodiesterase-5 inhibitors work? To achieve or maintain normal erectile function, nitric oxide (NO) is released from penile endothelial cells following sexual stimulation. The concentration of nitric oxide is significantly increased, which contributes to the conversion of guanosine triphosphate to cyclic guanosine monophosphate (cGMP). Downstream, cGMP decreases intracellular calcium ions in corpora cavernosa smooth muscle, resulting in smooth muscle relaxation causing vasodilation and reduced arterial blood drainage, thereby maintaining erection. Cyclic guanosine monophosphate is metabolized by the enzyme phosphodiesterase type 5, so it cannot maintain its erectile effects. Erectile dysfunction is a type of sexual dysfunction and is the inability to achieve or maintain a penile erection sufficient for sexual intercourse. Phosphodiesterase-5 inhibitors work by inhibiting (suppressing) the enzyme phosphodiesterase type 5. By inhibiting this enzyme, the metabolism of cyclic guanosine monophosphate is reduced and ultimately leads to the successful achievement and maintenance of an erection. PDE5 inhibitors also work to relax the smooth muscle cells of blood vessels in other parts of the body, such as the bladder and prostate, to reduce the symptoms of benign prostatic hyperplasia, and in the lungs to treat pulmonary arterial hypertension. When are phosphodiesterase-5 inhibitors used? Phosphodiesterase-5 inhibitors are recommended as first-line treatment for erectile dysfunction. Other disease conditions for which specific PDE5 inhibitors are approved for treatment include: Tadalafil is used to treat lower urinary tract symptoms due to benign prostatic hyperplasia with or without accompanying erectile dysfunction; Tadalafil and sildenafil are approved for the treatment of pulmonary arterial hypertension. PDE5 inhibitors have not been shown to be effective and are not approved for use in women to improve sexual response. What are the limitations of using phosphodiesterase-5 inhibitors? PDE5 inhibitors should not be taken or should be used with caution if any of the following risk factors are present: Cardiovascular disease such as angina, heart failure, irregular heart rhythm (arrhythmia) or previous heart attack (myocardial infarction); Low blood pressure (hypotension); High blood pressure (hypertension),which is not controlled; Suffered a stroke; Liver problems; Kidney problems or need for dialysis; Retinitis pigmentosa, a rare genetic eye disease; Suffered severe vision loss, including a condition called non-arterial anterior ischemic optic neuropathy (NAION); Stomach ulcers; Bleeding problem; Deformed shape of the penis or Peyronie’s disease; History of an erection lasting more than 4 hours; A disorder affecting blood cells such as sickle cell anemia, multiple myeloma, or leukemia; Hearing problems. Phosphodiesterase-5 inhibitors and other drugs can interact with each other. It is always necessary to consult a specialist before starting or stopping any treatment. Before starting to take a PDE5 inhibitor, it is necessary to notify the doctor if the patient is taking any of the following medications: Nitrates; Alpha blockers such as terazosin, tamsulosin, doxazosin, prazosin, alfuzosin, dutasteride, and tamsulosin or silodosin; Medicines to treat hypertension (high blood pressure); HIV protease inhibitors such as ritonavir; Certain oral antifungals such as ketoconazole or itraconazole; Certain antibiotics such as clarithromycin, telithromycin or erythromycin. What are the side effects of taking phosphodiesterase-5 inhibitors? Common side effects from taking PDE5 inhibitors include: Headache; Indigestion; Upset stomach; Dizziness; Back pain; Muscle pain; Redness; Nasal congestion; A runny nose. This is not an exhaustive list of the side effects of taking phosphodiesterase-5 inhibitors and it is always necessary to consult a specialist and seek medical advice about what side effects can be expected. Rare but significant side effects of taking phosphodiesterase-5 inhibitors that require immediate medical attention include: Priapism (an erection that lasts more than 4 hours); Sudden decrease or loss of vision in one or both eyes or changes in color vision; Sudden loss or decrease in hearing, sometimes with ringing in the ears and dizziness. References: 1. PubMed. Montague DK, Jarrow JP, Broderick GA, et al. The management of erectile dysfunction: An AUA update 2. Limin M, Johnsen N, Hellstrom JG. Avanafil, a new rapid-onset phosphodiesterase 5 inhibitor for the treatment of erectile dysfunction 3. PubMed. Carrier S. Pharmacology of phosphodiesterase 5 inhibitors 4. National Center for Biotechnology Information (NCBI). Sharon A. Huang, Janette D. Lie. Phosphodiesterase-5 (PDE5) Inhibitors In the Management of Erectile Dysfunction 5. SingleCare. PDE5 inhibitors: Uses, common brands, and safety informationcalled non-arterial anterior ischemic optic neuropathy (NAION); Stomach ulcers; Bleeding problem; Deformed shape of the penis or Peyronie’s disease; History of an erection lasting more than 4 hours; A disorder affecting blood cells such as sickle cell anemia, multiple myeloma, or leukemia; Hearing problems. Phosphodiesterase-5 inhibitors and other drugs can interact with each other. It is always necessary to consult a specialist before starting or stopping any treatment. Before starting to take a PDE5 inhibitor, it is necessary to notify the doctor if the patient is taking any of the following medications: Nitrates; Alpha blockers such as terazosin, tamsulosin, doxazosin, prazosin, alfuzosin, dutasteride, and tamsulosin or silodosin; Medicines to treat hypertension (high blood pressure); HIV protease inhibitors such as ritonavir; Certain oral antifungals such as ketoconazole or itraconazole; Certain antibiotics such as clarithromycin, telithromycin or erythromycin. What are the side effects of taking phosphodiesterase-5 inhibitors? Common side effects from taking PDE5 inhibitors include: Headache; Indigestion; Upset stomach; Dizziness; Back pain; Muscle pain; Redness; Nasal congestion; A runny nose. This is not an exhaustive list of the side effects of taking phosphodiesterase-5 inhibitors and it is always necessary to consult a specialist and seek medical advice about what side effects can be expected. The rare but significant side effects of taking phosphodiesterase-5 inhibitors that require immediate medical attention include: Priapism (an erection that lasts more than 4 hours); Sudden decrease or loss of vision in one or both eyes or changes in color vision; Sudden loss or decrease in hearing, sometimes with ringing in the ears and dizziness. References: 1. PubMed. Montague DK, Jarrow JP, Broderick GA, et al. The management of erectile dysfunction: An AUA update 2. Limin M, Johnsen N, Hellstrom JG. Avanafil, a new rapid-onset phosphodiesterase 5 inhibitor for the treatment of erectile dysfunction 3. PubMed. Carrier S. Pharmacology of phosphodiesterase 5 inhibitors 4. National Center for Biotechnology Information (NCBI). Sharon A. Huang, Janette D. Lie. Phosphodiesterase-5 (PDE5) Inhibitors In the Management of Erectile Dysfunction 5. SingleCare. PDE5 inhibitors: Uses, common brands, and safety informationcalled non-arterial anterior ischemic optic neuropathy (NAION); Stomach ulcers; Bleeding problem; Deformed shape of the penis or Peyronie’s disease; History of an erection lasting more than 4 hours; A disorder affecting blood cells such as sickle cell anemia, multiple myeloma, or leukemia; Hearing problems. Phosphodiesterase-5 inhibitors and other drugs can interact with each other. It is always necessary to consult a specialist before starting or stopping any treatment. Before starting to take a PDE5 inhibitor, it is necessary to notify the doctor if the patient is taking any of the following medications: Nitrates; Alpha blockers such as terazosin, tamsulosin, doxazosin, prazosin, alfuzosin, dutasteride, and tamsulosin or silodosin; Medicines to treat hypertension (high blood pressure); HIV protease inhibitors such as ritonavir; Certain oral antifungals such as ketoconazole or itraconazole; Certain antibiotics such as clarithromycin, telithromycin or erythromycin. What are the side effects of taking phosphodiesterase-5 inhibitors? Common side effects from taking PDE5 inhibitors include: Headache; Indigestion; Upset stomach; Dizziness; Back pain; Muscle pain; Redness; Nasal congestion; A runny nose. This is not an exhaustive list of the side effects of taking phosphodiesterase-5 inhibitors and it is always necessary to consult a specialist and seek medical advice about what side effects can be expected. Rare but significant side effects of taking phosphodiesterase-5 inhibitors that require immediate medical attention include: Priapism (an erection that lasts more than 4 hours); Sudden decrease or loss of vision in one or both eyes or changes in color vision; Sudden loss or decrease in hearing, sometimes with ringing in the ears and dizziness. References: 1. PubMed. Montague DK, Jarrow JP, Broderick GA, et al. The management of erectile dysfunction: An AUA update 2. Limin M, Johnsen N, Hellstrom JG. Avanafil, a new rapid-onset phosphodiesterase 5 inhibitor for the treatment of erectile dysfunction 3. PubMed. Carrier S. Pharmacology of phosphodiesterase 5 inhibitors 4. National Center for Biotechnology Information (NCBI). Sharon A. Huang, Janette D. Lie. Phosphodiesterase-5 (PDE5) Inhibitors In the Management of Erectile Dysfunction 5. SingleCare. PDE5 inhibitors: Uses, common brands, and safety informationNitrates; Alpha blockers such as terazosin, tamsulosin, doxazosin, prazosin, alfuzosin, dutasteride, and tamsulosin or silodosin; Medicines to treat hypertension (high blood pressure); HIV protease inhibitors such as ritonavir; Certain oral antifungals such as ketoconazole or itraconazole; Certain antibiotics such as clarithromycin, telithromycin or erythromycin. What are the side effects of taking phosphodiesterase-5 inhibitors? Common side effects from taking PDE5 inhibitors include: Headache; Indigestion; Upset stomach; Dizziness; Back pain; Muscle pain; Redness; Nasal congestion; A runny nose. This is not an exhaustive list of the side effects of taking phosphodiesterase-5 inhibitors and it is always necessary to consult a specialist and seek medical advice about what side effects can be expected. Rare but significant side effects of taking phosphodiesterase-5 inhibitors that require immediate medical attention include: Priapism (an erection that lasts more than 4 hours); Sudden decrease or loss of vision in one or both eyes or changes in color vision; Sudden loss or decrease in hearing, sometimes with ringing in the ears and dizziness. References: 1. PubMed. Montague DK, Jarrow JP, Broderick GA, et al. The management of erectile dysfunction: An AUA update 2. Limin M, Johnsen N, Hellstrom JG. Avanafil, a new rapid-onset phosphodiesterase 5 inhibitor for the treatment of erectile dysfunction 3. PubMed. Carrier S. Pharmacology of phosphodiesterase 5 inhibitors 4. National Center for Biotechnology Information (NCBI). Sharon A. Huang, Janette D. Lie. Phosphodiesterase-5 (PDE5) Inhibitors In the Management of Erectile Dysfunction 5. SingleCare. PDE5 inhibitors: Uses, common brands, and safety informationNitrates; Alpha blockers such as terazosin, tamsulosin, doxazosin, prazosin, alfuzosin, dutasteride, and tamsulosin or silodosin; Medicines to treat hypertension (high blood pressure); HIV protease inhibitors such as ritonavir; Certain oral antifungals such as ketoconazole or itraconazole; Certain antibiotics such as clarithromycin, telithromycin or erythromycin. What are the side effects of taking phosphodiesterase-5 inhibitors? Common side effects from taking PDE5 inhibitors include: Headache; Indigestion; Upset stomach; Dizziness; Back pain; Muscle pain; Redness; Nasal congestion; A runny nose. This is not an exhaustive list of the side effects of taking phosphodiesterase-5 inhibitors and it is always necessary to consult a specialist and seek medical advice about what side effects can be expected. Rare but significant side effects of taking phosphodiesterase-5 inhibitors that require immediate medical attention include: Priapism (an erection that lasts more than 4 hours); Sudden decrease or loss of vision in one or both eyes or changes in color vision; Sudden loss or decrease in hearing, sometimes with ringing in the ears and dizziness. References: 1. PubMed. Montague DK, Jarrow JP, Broderick GA, et al. The management of erectile dysfunction: An AUA update 2. Limin M, Johnsen N, Hellstrom JG. Avanafil, a new rapid-onset phosphodiesterase 5 inhibitor for the treatment of erectile dysfunction 3. PubMed. Carrier S. Pharmacology of phosphodiesterase 5 inhibitors 4. National Center for Biotechnology Information (NCBI). Sharon A. Huang, Janette D. Lie. Phosphodiesterase-5 (PDE5) Inhibitors In the Management of Erectile Dysfunction 5. SingleCare. PDE5 inhibitors: Uses, common brands, and safety informationwhich lasts more than 4 hours); Sudden decrease or loss of vision in one or both eyes or changes in color vision; Sudden loss or decrease in hearing, sometimes with ringing in the ears and dizziness. References: 1. PubMed. Montague DK, Jarrow JP, Broderick GA, et al. The management of erectile dysfunction: An AUA update 2. Limin M, Johnsen N, Hellstrom JG. Avanafil, a new rapid-onset phosphodiesterase 5 inhibitor for the treatment of erectile dysfunction 3. PubMed. Carrier S. Pharmacology of phosphodiesterase 5 inhibitors 4. National Center for Biotechnology Information (NCBI). Sharon A. Huang, Janette D. Lie. Phosphodiesterase-5 (PDE5) Inhibitors In the Management of Erectile Dysfunction 5. SingleCare. PDE5 inhibitors: Uses, common brands, and safety informationwhich lasts more than 4 hours); Sudden decrease or loss of vision in one or both eyes or changes in color vision; Sudden loss or decrease in hearing, sometimes with ringing in the ears and dizziness. References: 1. PubMed. Montague DK, Jarrow JP, Broderick GA, et al. The management of erectile dysfunction: An AUA update 2. Limin M, Johnsen N, Hellstrom JG. Avanafil, a new rapid-onset phosphodiesterase 5 inhibitor for the treatment of erectile dysfunction 3. PubMed. Carrier S. Pharmacology of phosphodiesterase 5 inhibitors 4. National Center for Biotechnology Information (NCBI). Sharon A. Huang, Janette D. Lie. Phosphodiesterase-5 (PDE5) Inhibitors In the Management of Erectile Dysfunction 5. SingleCare. PDE5 inhibitors: Uses, common brands, and safety information