Pharmacologic Therapy- Phsopho-diesterase Type 5 Inhibitors Flashcards
What is the mechanism of action of phosphodiesterase type 5 (PDE5) inhibitors?
PDE5 inhibitors work by inhibiting the enzyme phosphodiesterase type 5 (PDE5), which is responsible for the breakdown of cyclic guanosine monophosphate (cGMP) in smooth muscle cells of the corpus cavernosum in the penis.
How does inhibition of PDE5 lead to an erection?
By inhibiting PDE5, the breakdown of cGMP is reduced. This allows cGMP levels to rise, promoting smooth muscle relaxation in the corpus cavernosum and increasing blood flow to the penis during sexual stimulation, ultimately leading to an erection.
What is the role of cGMP in the mechanism of action of PDE5 inhibitors?
cGMP is a secondary messenger that helps relax smooth muscles in the penis by dilating blood vessels, increasing blood flow, and facilitating an erection.
PDE5 inhibitors prevent the breakdown of cGMP, enhancing its effect on smooth muscle relaxation.
Name a few examples of PDE5 inhibitors.
Examples of PDE5 inhibitors include sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra), and avanafil (Stendra).
How is cGMP regulated in the normal physiological state?
In the normal physiological state, cGMP levels are regulated by the balance between its production by guanylate cyclase and its breakdown by phosphodiesterase type 5 (PDE5). PDE5 inhibitors disrupt this balance by inhibiting the breakdown of cGMP.
What are the physiological effects of inhibiting phosphodiesterase isoenzyme 1
inhibition of phosphodiesterase isoenzyme 1 can lead to peripheral vasodilation, potentially lowering blood pressure, causing flushing, and reflex tachycardia, especially in patients taking nitrates, alpha-adrenergic antagonists, or certain antihypertensives
Which phosphodiesterase type 5 inhibitors have less selectivity for phosphodiesterase type 1, making them less likely to cause hypotension?
Tadalafil and avanafil have less selectivity for phosphodiesterase type 1 compared to phosphodiesterase type 5, making them less likely to cause hypotension compared to sildenafil and vardenafil.
What physiological effects are associated with inhibiting phosphodiesterase isoenzyme type 6?
Inhibition of phosphodiesterase isoenzyme type 6, localized in the retina, has been associated with blurred vision and cyanopsia (seeing everything tinted blue). Sildenafil is the most potent inhibitor, vardenafil is intermediate, and tadalafil and avanafil are the least potent inhibitors of this isoenzyme.
Inhibition of which phosphodiesterase isoenzyme is linked to myalgia and back muscle pain?
Inhibition of phosphodiesterase isoenzyme type 11, localized in skeletal muscle, has been associated with myalgia and back muscle pain. Tadalafil exerts the greatest inhibitory activity against this isoenzyme.
Phosphodiesterase isoenzyme type 6 is primarily localized in skeletal muscles.
False
Inhibition of phosphodiesterase isoenzyme type 6 is associated with blurred vision and cyanopsia.
True
Phosphodiesterase isoenzyme type 11 is localized to skeletal muscle.
True
Phosphodiesterase isoenzyme type 1 is found in the _______________.
Peripheral vasculature.
Sildenafil is the most potent inhibitor of phosphodiesterase isoenzyme type ____________.
6
inhibition of phosphodiesterase isoenzyme type 11 has been associated with _______________.
Myalgia and back muscle pain.
