2023-06-05 15:51:24
Definition: what is a vasodilator drug?
THE vasodilators group together a heterogeneous set of drugs whose main effect is to dilate blood vessels and therefore to increase the caliber of the latter.
Why take vasodilators? In what directions?
The main effect of vasodilator drugs is to lower blood pressure. So their principale indication is the treatment of systemic hypertension.
They are also prescribed for:
- improve certain heart and vascular disorders such as heart and coronary failure (angina pectoris or angina) or the Raynaud’s disease ;
- once morest sexual impotence where the urological disorders in man.
Vasodilators can indeed have a specific action on certain vessels such as:
- THE coronary (heart failure, angina, myocardial infarction);
- THE cerebral arteries (stroke, TIA, dizziness, migraines, etc.);
- THE lower limb arteries (obliterating arteriopathy of the lower limbs);
- the vcapillaries(Raynaud’s syndrome, androgenic alopecia);
- THE eye vessels (ocular hypertension);
- THE genital and urinary tract vesselss (benign prostatic hyperplasia, male impotence).
What are the different types of vasodilator drugs?
There are many classifications of vasodilators. The most used is that which classifies them according to their site of action. A distinction is thus made between predominantly venous vasodilators, vasodilators which act on the arteries and those which act on these two types of vessels (mixed vasodilators).
Predominantly venous vasodilators (nitro derivatives, sydonimines), sources of nitric oxide
- Nitrates (trinitrine, isosorbide dinitrate, nitroglycerin, isosorbide mononitrate, pentaerythrityl tetranitrate.…) who are nitric oxide (NO) donors. NO leads to relaxation of vascular smooth muscle fibers. Systemically, trinitrine is used in the management of angina, ventricular failure, myocardial ischemia, acute pulmonary edema. Locally, trinitrine is used in the management of anal fissures.
- THEsydnonimines (molsidomine) which are also NO donors. They are given to treat angina pectoris (angina).
Predominantly arterial vasodilators (calcium channel blockers, direct vasodilators, alpha-blockers, central antihypertensives)
- Calcium channel blockers (nifedipine, nicardipine, amlodipine, felodipine, isradipine, diltiazem, verapamil, etc.) which act at the level of the calcium channels by slowing down the entry of calcium into the vascular smooth muscle cells and the cardiomyocytes. They are indicated in the treatment of various cardiac disorders such as angina pectoris, arrhythmias or arterial hypertension.
- Direct vasodilators (hydralazine, dihydralazine, monoxidil, etc.) which have the exclusive effect of relaxing the smooth muscle of the arterial wall. They are effective once morest high blood pressure. Applied locally, monoxidil helps to treat alopecia.
- Alpha-blockers or alpha-adrenolytics (prazosine, urapidil, etc.) are drugs that oppose the vasoconstrictor effects of adrenaline and noradrenaline. They were first used in cardiology as antihypertensives. Today, they are also used in urology to reduce the symptoms of prostatic adenoma called benign prostatic hyperplasia.
- Central antihypertensives (clonidine, methyldopa, moxonidine, rilmenidine, etc.) which are third- or fourth-line treatments for essential hypertension and which are used in combination with other antihypertensives. They are often prescribed in case of gravidic hypertension (during pregnancy). These drugs are presynaptic agonists of the alpha-2 type acting on the bulbar cardiomoderator centers and they all have a more or less marked central sympatholytic effect.
Mixed vasodilators (angiotensin converting enzyme inhibitors, angiotensin 2 receptor antagonists)
- ACE inhibitors (captopril, enalapril, lisinopril, ramipril, etc.) are used in particular in the treatment of high blood pressure, coronary artery disease and chronic heart failure. These drugs are angiotensin converting enzyme inhibitors which are part of a cascade regulating blood pressure.
- Angiotensin 2 receptor antagonists or ARA 2 (candesartan, eprosartan, irbesartan, losartan, telmisartan and valsartan…) which block the action of an enzyme called angiotensin II which causes blood vessels to tighten. They are indicated, alone or in combination with a thiazide diuretic, in the treatment of arterial hypertension in adults.
Mode of action: how do vasodilators work?
A vasodilator can act:
- a direct effect on smooth muscle cells (by stimulation of their vasodilator receptors, by inhibition of calcium influx, by activation of potassium channels or even by their action on the metabolism of AMP or cyclic GMP);
- an indirect effect via the release of so-called “endothelial” factors (NO, prostacyclin, hyperpolarizing factors);
- inhibition of the formation of endogenous vasoconstrictors (angiotensin converting enzyme inhibitors) or their effects.
Either way, the effect is the same: the diameter of blood vessels is increased. This vasodilation therefore has the effect of lowering blood pressure. It also increases the blood flow in the vessels and leads to the acceleration of the heart rate.
Vasodilators: are there any contraindications?
The main contraindication to taking these drugs is significant low blood pressure. In addition, precautions should be taken when taking anticoagulants (since vasodilators then increase the hemorrhagic risk). Finally, special monitoring, in particular of the blood pressure and some cardiac frequency, should be used throughout the duration of vasodilator therapy.
What are the side effects of vasodilators?
Like most medications, vasodilators can cause side effects. These depend on the type of vasodilators administered, the dosage and the patient profile. The main adverse effects listed are:
- hypotension (low blood pressure);
- dizziness ;
- malaise and fainting;
- orthostatic hypotension (low blood pressure when standing up quickly);
- headaches (headaches);
- hot flashes and redness of the face (flushes);
- heart palpitations;
- arrhythmia (tachycardia or bradycardia);
- nasal congestion (stuffy nose);
- digestive disorders (stomach aches, nausea, etc.).
Some vasodilators can cause more serious side effects such as mouth ulcersof the esophagitisskin disorders or even kidney damage (renal lithiasis) or hepatic. Alcohol consumption, which is also a powerful vasodilator, can intensify these effects.
1686148990
#Vasodilators #antihypertensives
