💨 Deck 5 – PDE Inhibitors, Prostaglandins, Endothelin Antagonists, and Other Vasodilators pcol exam 3

What is the mechanism of ranolazine

Inhibits late Na⁺ current in cardiac myocytes → ↓Na⁺-Ca²⁺ exchange → ↓Ca²⁺ overload → improved myocardial relaxation and O₂ efficiency.

What is ranolazine used for

Chronic stable angina (not for acute attacks).

What are adverse effects of ranolazine

Dizziness, constipation, nausea, QT prolongation (rare).

What is the mechanism of PDE-5 inhibitors

Inhibit phosphodiesterase-5 → prevent cGMP breakdown → ↑cGMP → smooth muscle relaxation → vasodilation.

List common PDE-5 inhibitors. Sildenafil (Viagra/Revatio), tadalafil (Cialis), vardenafil (Levitra), avanafil (Stendra).

What are PDE-5 inhibitors used for

Erectile dysfunction and pulmonary arterial hypertension (PAH).

How do PDE-5 inhibitors cause penile erection

Enhance NO–cGMP pathway → relaxation of corpus cavernosum smooth muscle → increased blood flow.

Why are PDE-5 inhibitors contraindicated with nitrates

Excessive cGMP → profound hypotension → syncope or MI.

What are common adverse effects of PDE-5 inhibitors

Headache, flushing, nasal congestion, hypotension, reflux, blue-tinged vision (PDE-6 inhibition).

Which PDE-5 inhibitor has the longest duration of action

Tadalafil.

What is priapism and how is it treated

Persistent erection >4 hours; treated with intracavernosal phenylephrine (α1 agonist).

What is alprostadil and how does it work

PGE1 analog → ↑cAMP → vasodilation; used for erectile dysfunction (injection or urethral suppository).

What are prostaglandin analogs used in ophthalmology

PGF2α analogs (latanoprost, travoprost, bimatoprost, tafluprost) → ↑uveoscleral outflow → ↓IOP (glaucoma).

What is the main adverse effect of prostaglandin eye drops

Iris pigmentation (darkening) and eyelash growth.

What are PGE2 and PGF2α analogs used for in obstetrics

Dinoprostone (PGE2) and carboprost/dinoprost (PGF2α) induce labor or control postpartum hemorrhage via uterine contraction.

Which prostaglandin analog is used to maintain PDA in neonates

Alprostadil (PGE1 analog).

What are prostacyclin (PGI2) analogs used for

Pulmonary arterial hypertension (PAH) – epoprostenol, iloprost, treprostinil, selexipag.

What is the mechanism of prostacyclin analogs

Activate IP receptors → ↑cAMP → vasodilation and inhibition of platelet aggregation.

What are adverse effects of prostacyclin analogs

Flushing, headache, jaw pain, hypotension, diarrhea.

What are endothelin receptor antagonists

Bosentan, ambrisentan, macitentan – block endothelin A (ETA) receptors → vasodilation.

What is endothelin’s normal physiological effect

Potent vasoconstriction and smooth muscle proliferation.

What are endothelin receptor antagonists used for

Pulmonary arterial hypertension (PAH).

What are adverse effects of bosentan and related drugs

Hepatotoxicity, edema, teratogenicity, anemia.

What is riociguat and how does it work

Soluble guanylate cyclase stimulator → ↑cGMP → vasodilation (used in PAH and chronic thromboembolic PH).

What are common adverse effects of riociguat

Hypotension, dizziness, GERD, headache.

Which PDE enzyme predominates in pulmonary vasculature

PDE-5.

What happens if PDE-5 inhibitors are combined with riociguat

Excessive cGMP accumulation → severe hypotension (contraindicated).

Which smooth muscle does NO-cGMP signaling relax in the lower esophagus

Lower esophageal sphincter → can cause reflux as an adverse effect.