How Do PAH PDE-5 Inhibitors Work?

PAH phosphodiesterase-5 (PDE-5 inhibitors) are medications used to treat pulmonary arterial hypertension (PAH), a condition of high blood pressure in the arteries that carry deoxygenated blood from the heart to the lungs. PDE-5 inhibitors are also used to treat erectile dysfunction and enlarged prostate.

PDE-5 inhibitors relax the smooth muscles of the pulmonary arteries, dilating them and reducing the pulmonary blood pressure. PDE-5 inhibitors improve blood flow to the penis and also relieve urinary symptoms associated with an enlarged prostate.

PDE-5 inhibitors work by blocking the activity of PDE-5, an enzyme that plays a role in the contraction of smooth muscles around blood vessels. PDE-5 inhibitors prevent the PDE-5 enzyme from stimulating PDE-5 receptors, a type of protein molecule that is abundant in the smooth muscles of pulmonary blood vessels and the penis.

Inhibition of the PDE-5 enzyme increases the concentration of a signaling molecule known as cyclic guanosine monophosphate (cGMP), which leads to relaxation of vascular smooth muscles, dilation of blood vessels, and improved blood flow.

PAH PDE-5 inhibitors are administered orally as tablets or suspensions, or as intravenous injections in the treatment of the following conditions:

FDA-approved:

• Pulmonary arterial hypertension: To improve exercise ability and slow down the progression of disease in patients with:
  • Idiopathic PAH
  • Inherited PAH
  • PAH caused by connective tissue diseases
• Erectile dysfunction
• Benign prostatic hyperplasia (prostate enlargement)

Orphan designation:

• Duchenne muscular dystrophy (an inherited muscle degeneration disorder)

Side effects of PAH PDE-5 inhibitors may include the following:

• Headache
• Myalgia (muscle pain)
• Respiratory tract infection
• Nasopharyngitis (inflammation of nose and throat)
• Nasal congestion
• Bronchitis (inflammation of the bronchial passage
• Dyspepsia (indigestion)
• Nausea
• Gastroesophageal reflux disease (GERD)
• Diarrhea
• Dizziness
• Flushing
• Back pain
• Arthralgia (joint pain)
• Insomnia (sleeplessness)
• Skin rash
• Erythema (redness of the skin)
• Hypertension (high blood pressure)
• Angina pectoris (chest pain)
• Hypotension (low blood pressure)
• Genitourinary tract infection
• Amnesia (memory loss)
• Change in color vision
• Conjunctival hyperemia (dilation and redness of blood vessels in the conjunctiva, the membrane on the whites of the eyes, and the inner surface of eyelids)
• Visual field defect
• Retinal vein occlusion (block)
• Non-arteritic anterior ischemic optic neuropathy (NAION), a condition that causes loss of blood flow and damage to the optic nerve
• Dyspnea (shortness of breath)
• Epistaxis (nasal bleeding)
• Hearing loss
• Priapism (persistent and painful erection)
• Blood vessel block in people with sickle cell anemia

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of PAH PDE-5 inhibitor drugs include:

• Adcirca
• Alyq
• Cialis
• Revatio
• sildenafil
• tadalafil
• Viagra