let us discuss fast forward diesterase 5 inhibitors. What are the precautions, side effects, and clinical use of these drugs? We will discuss in this video. Fast forward diesterase is one of the cleavage enzyme, which is commonly known as PDE. This PDE is a group of enzymes, which are classified into different categories like PDE type 1, 2, type 11. So we have various types of PDE Enzymes, which are responsible for different type of physiological actions.
Among these phosphodisesterase Enzymes, PDE5 is one of the important enzyme on which few of the drugs are going to act. And those drugs which are blocking the PDE5 enzyme activity are recognized with simple suffix Efil. So we have drugs like Sildenafil, Tadellafil, VADENAfil, Avenafil. These are the four drugs which are classified as PDE 5 inhibitors. All these drugs are hang the same suffix, Efil.
These drugs can be used in the treatment of erectile dysfunction as these drugs produce the relaxation of carpus cavernosum. Similarly, drugs like Sildenafil can also be used for the treatment of pulmonary hypertension. Sildenafil can be used for both erectile dysfunction as well as for pulmonary hypertension. Pd5 inhibitors can also be used in the treatment of benign prosthetic hyperplasia, commonly known as BPH, which is associated with prostate enlargement.
Read More: Letrozole Precautions and side effects
In such conditions, mainly alpha one blockers can be used. But in severe conditions of BPH, tredolophil can be used at a dose of 5 mg in those patients who are having both erectile dysfunction as well as benign prosthetic hyperplasia. Now, what is this fast f oot diesterase enzyme? This is one of the cleavage enzyme.
This cleaves the fast f oot diester bonds, but these fast f oot diester bonds are present in many of the molecules. Now, PDE5 is not acting on all types of fast f oot diester bonds. It particularly acting on the cyclic nucleotide fast f oot esters linkages. For instance, cyclic AMP and cyclic GMP are the cyclic nucleotides on which these type of enzymes can act.
But PDE5 mainly targets the cyclic GMP. Cyclic DMP is one of the cyclic nucleotide. And here this is the diester bond formed between gunocin and phosphate bond. Now this cyclic fast f oot ester bond is going to be cleaved by PDE5 enzyme so that cyclic DMP is going to be converted into GTP. Drugs with suffix Efil or the PDE5 inhibitors, they can act on the PDE5 enzyme. Thereby, they can inhibit the engematic activity which results in the decreased cleavage of Cyclic DMP.
Therefore, the Cyclic DMP levels are going to be increased with these drugs. So as the Cyclic DMP levels are increased, they increase the relaxation of carpus cavernosum, as well as they also increase the vaso dilatation within this tissue, resulting in the increased erection. That’s why these drugs can be used in the treatment of erectile dysfunction. And even they produce systemic vaso dilatation and they can reduce the pulmonary blood pressure.
So drugs like Sildenafil can be used in the treatment of pulmonary hypertension. Now, let us see the precautions of fast forward S 5 inhibitors. First precaution is the hypotension. Pde5 inhibitors can act on the blood vessels and they can produce vaso dilatation along with relaxation of carpus cavernosome and vaso dilatation of blood vessels.
They can also produce some systemic vaso dilatation, resulting in decreased blood pressure. So hypotension is one of the important effect that can be observed with PDE 5 inhibitors. This is more important when these drugs are combined with alcohol, since alcohol can also produce vasodilatation. So along with alcohol, PDE 5 inhibitors should be carefully used in order to avoid significant hypotension. These drugs may produce few other symptoms such as dizziness, light headedness and headache because of cranial vasodilatation.
These drugs can also increase the heart rate because of vasodilatation, which stimulates a reflex action on the heart, resulting in the increased heart rate. So all these effects can be produced by fast forward S5 inhibitors.
So they should be carefully used along with the alcohol. Even along with other drugs, they should be carefully combined. For instance, organic nitrates such as glyceryl trinitrate, isosorbid dinitrate, isosorbate mononitrate, all these drugs are indicated for the management of angina. These drugs can produce severe hypotension when they are combined with PDE5 inhibitors. So organic nitrate should not be combined with PDE5 inhibitors. So they are strictly contraindicated with PDE5 inhibitors.
On the other hand, few of the drugs like TCBs, calcium channel blockers, and other vasodilators like alpha one blockers, they can also produce hypotension, but they are not contraindicated with PDE 5 inhibitors. Instead, they should be carefully used in order to avoid severe hypotension. So when these drugs are coadmitted with PDE 5 inhibitors, the dosage adjustment should be done in order to reduce the hypotensive effect. Second one is the cardiovascular effects. Pde5 inhibitors should be carefully used in the patients with already existing cardiovascular disorders. Because these drugs can produce hypotension and they may also increase the tachycardia due to reflux action.
So PD5 inhibitors can also increase the chest pain and also increase the risk of unstable angina and myocardial infarction. So in those patients with pre existing cardiovascular disorders, these drugs should be carefully used. Third is the ophthalmic effects. These drugs can also affect the vision and particularly they can produce optic neuropathy. This condition is specifically called as non aortic anterior ischemic optic neuropathy.
These drugs can increase the ischemia, thereby they can reduce the blood flow, which results in the neuropathy. And if this is untreated, it may also lead to some loss of vision. This particular effect can be observed with many of the PDE5 inhibitors. As these drugs can also block the enzyme activity of PDE6 enzyme.
This fast food stress type 6 enzyme is present on the retina of eye. So when this enzyme activity is inhibited, it may increase the neuropathy that may lead to visual defects, and finally, it may lead to loss of vision. So any decrease in the optical acuity should be carefully monitored in the patients who are administered with PDE 5 inhibitors.
Fourth one is the Priapism. This is commonly observed with PDE 5 inhibitors, but these drugs are going to act on erectile tissueand they produce the relaxation of carpus cavernosum, which may lead to prolonged erection for more than six hours.
Erection can be observed with these drugs, which may produce some painful erection. Fifth one is the Vistubular effects. Since PDE 5 inhibitors produce hypotension, you can also produce some Vistubular disturbances. These drugs may produce tinnitus, some budging noise in the ear, as well as they can also produce some hearing loss. So in those patients with pre existing Vistubular disorders, these drugs should be carefully used.
Now, let us the side effects of PDE 5 inhibitors. These drugs mainly produce headache because of cranial vascular dilatation. They also produce flushing, increased redness of the skin as well as face. And their important side effect is the dizziness and light headedness produced by these drugs. As of cardiovascular effects, they can also increase the chest pain and induction of unstable angina. Even they can produce some dysphexia, indigestion. It can also produce some back pain. Other side effects mainly include nasal congestion.
They can also produce some pharyngitis. Loss of hearing is another important side effect that can be observed with these PDE 5 inhibitors. So these are the important precautions and side effects of PDE 5 inhibitors. Clearly, these drugs produce higginess, light headedness, increase the heart rate, and they can also increase the chest pain and increase the risk of myocardial infarction.
So the patients with cardiovascular disorders, these drugs should be carefully used. And because of high potency of effect, these drugs should not be combined with organic nitrates, but with other vasodilators, they should be carefully used.
These drugs may also produce loss of vision and hearing loss. So in the patients with pre existing vascular disorders, these drugs should be carefully given.
