nitroglycerin

isosorbide dinitrate

amyl nitrate

Mechanism: NO activates Guanylate cyclase leading to increase cGMP. Increased cGMP causes activation of cGMP-dep protein kinase phosphorylation cascade which eventually leads to dephosphorylation of myosin light chain and muscle relaxation.

Low Doses: Venodilation, venous pooling

High Doses: Dec. peripheral resistance

Overall: Dec. Heart Size and wall tension during systole

Treatment: suppression of acute attacks

Side-Effects: Hypotension, headache, flushing, GI distress,

Sildenafil (Viagra)

Vardenafil (Levitra)

Tadalafil (Cialis)

Mechanism: Phosphodiesterase 5 Inhibitor that blocks cGMP from being degraded to GMP. More cGMP leads to increased dephosphorylation of MLC-PO4 to Myosin-LC causing relaxation

Treatment: ED

Side Effects: low toxicity

Nifedipine (DHPs)

Nicardipine

Mechanism: calcium entry blocker. bind to closed L-channels and decrease frequency of opening. Systemic vasodilation of resistance, coronary artery vasodilation causing increased blood flow, cardiac suppressive effects by reflex

Treatment:

Side-Effects: Flushing, headaches, hypotension, peripheral edema

Verapamil

(Diltiazem)

Mechanism: moderate vasodilation. cardiac suppression largely balanced by reflex activation; thus CO and HR only modestly decreased.

Diltiazem is similar but less suppressive heart effects

Treatment:

Side-Effects: Contraindicated in severe CHF, some alpha-adrenergic blockade, flushing, GI disturbance, left ventricular dysfunction