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Sildenafil is a substance that gives many men a chance to have intercourse. It is a component of, among others popular Viagra, i.e. a drug used to treat erectile dysfunction. How does sildenafil work? How does it affect the body? What are the indications and contraindications for the use of sildenafil?
Sildenafil – action
Sildenafil can be used to treat erectile dysfunction (impotence) in men or pulmonary hypertension in men and women. Sildenafil blocks the action of an enzyme known as cGMP type 5 specific phosphodiesterase (PDE-5). This enzyme breaks down cGMP, a substance that causes smooth muscles to relax.
Blocking PDE-5 means elevated levels of cGMP in smooth muscle, which promotes muscle relaxation and vasodilation (widening of blood vessels). High levels of PDE-5 are found in the penis, lungs, and retina. PDE-5 is also found throughout the body in smooth muscle cells, blood vessels and muscles. Sildenafil belongs to a group of medicines known as selective phosphodiesterase (PDE) type 5 inhibitors.
Also read: Inflammation promotes the formation of blood vessels
Sildenafil – effect on the body
Sildenafil increases blood flow to the penis after sexual stimulation. It does this by blocking the enzyme responsible for breaking down cGMP. cGMP is a substance that relaxes and widens blood vessels and smooth muscle cells. This allows men to maintain an erection strong enough during sexual intercourse. Sildenafil (a brand of Viagra) only works after sexual stimulation. It works for 30 to 60 minutes, but can be taken up to four hours before sexual activity.
Sildenafil lowers the high blood pressure associated with pulmonary arterial hypertension (PAH). This improves exercise capacity in people with PAH and delays the worsening of their symptoms. Revatio is available as a generic medicine called sildenafil (20 mg tablet). There is also a generic version of Viagra called sildenafil in 25 mg, 50 mg and 100 mg strengths.
Read also: Malignant hypertension is deadly. What kind of illness is that?
Sildenafil – side effects
The following side effects are likely to occur with sildenafil-based preparations:
- indigestion, hot flush, headache, muscle or back pain and visual disturbances are often reported.
- Other side effects include drop in blood pressure, insomnia, nasal congestion or runny nose and nosebleeds. Sudden hearing loss has also been reported
- blood flow to the optic nerve may be reduced, causing sudden loss of vision. The risk is greater in people over the age of 50, with diabetes, heart disease, high blood pressure, high cholesterol, smoking, or some pre-existing eye problems.
Sildenafil can cause other side effects or lead to painful erections lasting more than four hours. If this happens, see your doctor immediately.
Sildenafil may not be suitable for some people, including those with angina, chest pain or other heart conditions, liver or kidney problems, blood or bleeding disorders, stomach ulcers, certain eye conditions, or a physical deformity of the penis (such as Peyronie).
Sildenafil may interact with certain medications, including certain antibiotics and antifungal agents, herbal remedies, HIV medications, nitrates, and medications used to treat high blood pressure or prostate disorders. Sildenafil should not be taken with other PDE-5 inhibitors.
The dose may need to be reduced in people with kidney or liver problems. More research is needed to determine if sildenafil plays a role in female sexual dysfunction.
Sildenafil does not protect against sexually transmitted diseases.
Sildenafil – interactions with other drugs
Drugs that interact with sildenafil may either reduce its effect, affect the duration of its action, and increase side effects, when taken with sildenafil.
Medicinal products that may interact with sildenafil include:
- alpha agonists (e.g. clonidine, methyldopa)
- alfa-blokery (np. alfuzosin, doxazosin, prazosin, tamsulosin lub terazosin),
- antibiotics such as azithromycin, clarithromycin, erythromycin, metronidazole, norfloxacin, rifabutin, rifampicin or tetracycline
- antidepressants such as desipramine, sertraline or St. John’s wort
- antifungals such as itraconazole, ketoconazole or voriconazole
- beta-blockers such as atenolol or propranolol
- warfarin
- cimetidine,
- drugs for cystic fibrosis, such as ivacaftor
- epilepsy drugs such as carbamazepine, oxcarbazepine, phenobarbital, phenytoin or primidone
- other erectile dysfunction drugs (e.g. alprostadil, vardenafil),
- heart medications such as amlodipine, amiodarone, atenolol, bosentan, candesartan, captopril, clonidine, diltiazem, enalapril, irbesartan, losartan, nifedipine, propranolol, sotalol or verapamil
- medicines for hepatitis such as boceprevir and simeprevir
- HIV medicines (e.g. atazanavir, delavirdine, efavirenz, fosamprenavir, indinavir, etravirine, ritonavir, nevirapine, saquinavir or tipranavir)
- nitrates (e.g. amyl nitrate, isosorbide dinitrate, isosorbide mononitrate or nitroglycerin): separate administration over 24 hours.
- tolbutamide,
- others such as aprepitant, butalbital, cimetidine, cyclosporine, riociguat, or imatinib.
Taking sildenafil with too much alcohol can lead to orthostatic hypotension, which is a drop in blood pressure when moving from sitting or lying down to standing. Symptoms include pain and dizziness or fainting when standing.
Antacids such as magnesium hydroxide or aluminum hydroxide can also affect the absorption of sildenafil. Grapefruit juice may also increase the side effects of sildenafil.
Please note that this list is not intended to be exhaustive and only includes common medications that may interact with sildenafil.
How to replace sildenafil?
The original sildenafil has been on the market since 1998. Today you can get other preparations with a similar effect. In addition to prescription drugs, you can also get various herbal preparations in pharmacies to help men with mild and moderate erectile dysfunction.
You can buy many different specifics online. These are preparations in tablets, gel or powder. Unfortunately, not only sildenafil can be found in their composition. Therefore, when using such preparations, you have to take into account the risk of various side effects, such as headaches, backaches, or rashes that are difficult to treat.