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Drugs for the treatment of ED

Drugs for the treatment of ED

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Drugs for the treatment of ED

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  1. Basic & Clinical Pharmacology Drugs for the treatment of ED

  2. Causes of ED Cause: 1. psychological, 2. Physical injury, 3. Drug-induced, 4. Life-style, 5. Diseases, such as DM Prevalence 10% CMAJ 2004;170(9):1429-37.

  3. Anatomy of penis and its erection 1. increased blood flow to the penis, 2. relaxation of cavernous smooth muscle, 3. restriction of venous outflow. CMAJ 2004;170(9):1429-37.

  4. Mechanism governing the SM contraction 1. Parasympathetic never 2. Sympathetic never Reviews in urology 2002;4(S3): S17-25.

  5. Parasympathetic never governing the erection NO—GC—cGMP—PKG—Ca2+ PDE5 inhibitor Reviews in urology 2002;4(S3): S17-25.

  6. Sympathetic never governing the erection Agents that 1) raise cGMP, 2) raise cAMP, 3) prevent IP3 formation, or 4) inhibit Rho kinase can initiate or facilitate penile erection. Reviews in urology 2002;4(S3): S17-25.

  7. Drugs for ED Classification 1. Phosphodiesterase (PDE) inhibitors Nonselective (papaverine) PDE5-selective (sildenafil, tadalafil, vardenafil) 2.α-Adrenergic-receptor antagonists Nonselective α1/ α2 (phentolamine) α 1-selective (moxisylyte) 3. Adenylate cyclase activators (VIP, CGRP, forskolin, PGE1) 4. NO donors (linsinomine) 5. K channel openers 6. Dopamine agonists Nonselective D1/D2 (apomorphine) Selective D2 (sumanitrole) 7. Serotonergic (mCPP, trazodone) 8. Melanocortin agonists (melanotan II) 9. Opiate antagonists (naltrexone)

  8. A. Intracavernous/topical/intraurethral agents Peripheral initiators • Papaverine:a nonselective phosphodiesterase inhibitor. • Phentolamine:a competitive α-adrenergic-receptor antagonist • Thymoxamine(moxisylyte): an α1 antagonist • Prostglandin E1:most commonly used • VIPs: in combination with other such as phentolamine • Linsidomine chlorohydrate: an NO donor along with sodium nitroprusside

  9. B. Oral/sublingual agents Oral/sublingual agents • Yohimbine:pre-synaptic α2 antagonist • PDE5 selective inhibitors: • (sildenafil, tadalafil, vardenafil) caffeine is a weak PDE5 inhibitor

  10. B. Oral/sublingual agents • Phosphodiesterase type 5 isoenzyme inhibitors (PDE5I) • Sidenafil (西地那非,万艾可) • Vardenafil (伐地那非,爱力达) • Tadalafil (他达那非,希爱力)

  11. B. Drugs used to treat erectile dysfunction

  12. B. Drugs used to treat erectile dysfunction Sildenafil citrate(Viagra) • Acts by inhibiting cGMP-specific PDE5, an enzyme that delay degradation of cGMP, which regulates blood flow in the penis • The prime treatment for erectile dysfunction in all settings, including diabetes.

  13. B. Drugs used to treat erectile dysfunction Clinical uses (1) Sexual dysfunction (2) Pulmonary arterial hypertension (PAH) • relaxes the arterial wall, leading to decreased pulmonary arterial resistance and pressure→workload of the right ventricle ↓, symptoms of right-sided heart failure↑ • acts selectively in the lungs and penis without inducing vasodilation in other areas of the body →PDE-5 is primarily distributed within the arterial wall smooth muscle of the lungs and penis (3) Altitude sickness • prevention and treatment of high-altitude pulmonary edema associated with altitude sickness -such as that suffered by mountain climbers.

  14. B. Drugs used to treat erectile dysfunction Adverse effects 1.Headache, flushing, dyspepsia, nasal congestion and impaired vision, including photophobia and blurred (lead to vision impairment in rare cases) - the most common adverse effects 2. Priapism, severe hypotension, myocardial infarction (heart attack), ventricular arrhythmias, stroke, increased intraocular pressure, and sudden hearing loss -rare but serious

  15. B. Drugs used to treat erectile dysfunction • Contraindications • Administration of nitric oxide donors • Recent stroke or heart attack, or in men for whom sexual intercourse is inadvisable due to cardiovascular risk factors • Hypotension (low blood pressure) • Severe hepatic/ renal function impairment • Hereditary degenerative retinal disorders (including genetic disorders of retinal phosphodiesterases)

  16. Further reading 1.Bertram G. Katzung, Susan B. Masters, Anthony J. Trevor Chapter 40. The Gonadal Hormones & Inhibitors Basic and Clinical Pharmacology, 11e. 2010 The McGraw-Hill Companies. 2.