Dilating drugs

Direct-acting vasodilators lower the peripheral vascular resistance mainly by causing arteriolar dilation. Drugs discussed are nitroprusside, hydralazine, minoxidil, and diazoxide. 

In patients with elevated systemic vascular resistance and normal-to-elevated systemic blood pressure, afterload reduction with nitroprusside is logical it should be emphasized that nitroprus-side also increases venous capacitance, thereby also decreasing preload. In the context of myocardial dysfunction, afterload reduction will typically lead to improved forward cardiac output. Nitroprusside may also be effective when the systemic vascular resistance is elevated and systemic blood pressure is reduced the caveat in this more complex hemodynamic setting is that the load reduction produced by nitroprusside must be counterbalanced by an increase in stroke volume. This derivative increase in stroke volume may not occur in the patient with advanced heart failure rather, the result will be a further reduction in mean arterial pressure and the potential risk of peripheral organ hypoperfusion. An alternative approach would be the use of an inotropic-dilator drug such as milrinone, which will provide both preload and afterload reduction its concurrent positive inotropic effect may offset the reduction in mean arterial pressure that can occur from vasodilation alone. 

Bamethane sulfate (V), a dilator drug known for many years, was recently employed in two studies involving patients with obliterative atherosclerosis and intermittent claudica-tion30/31. There was distinct clinical improvement in 7 patients. One patient, who failed to show improvement in lower limb circulation, nevertheless had some relief from the manifestations of concomitant cerebral arterial disease O. 

Physiological responses to prostaglandins encompass a variety of effects Some prostaglandins relax bronchial muscle others contract it Some stimulate uterine con tractions and have been used to induce therapeutic abortions PGEj dilates blood vessels and lowers blood pressure it inhibits the aggregation of platelets and offers promise as a drug to reduce the formation of blood clots... 

Thiirane is more bactericidal than oxirane, and derivatives of 2-mei captomethylthiirane inhibit tuberculosis. The following pharmacological uses have been reported for compounds derived from thiirane derivatives gold complexes of the adducts of diethylphosphine and thiirane (antiarthritic), adducts of thiiranes and malononitrile (antibacterial, blood vessel dilators, muscle relaxants, sedatives), thermolysis products of thiirane 1-oxides and adducts of thiirane 1-oxides with sulfenyl chlorides (antibacterial), adducts of 2,3-diarylthiirene 1,1-dioxides with ynamines (antibacterial, parasiticidal), adducts of 2,3-diarylthiirene 1,1-dioxides with enamines (antifertility), adducts of p-aminophenylacetic esters with thiirane (immunosuppressants), adducts of amines and thiiranes (radioprotective drugs). 

The crude drug, Adhatoda vasica, is used in India as a remedy for asthma. According to Chopra, vasicine produces broncho-dilation and might be used clinically as an expectorant. A detailed pharmacological examination of peganine in comparison with harmine has been made by Tutaev and Makarova. ... 

Sympathomimetic. A drug that produces effects similar to stimulating the sympathetic nervous system, that is, increased blood pressure, dilated bronchi, and mydriasis. 

Prostacyclin (epoprostanol) is one of the few drugs effective for the treatment of Primary Pulmonary Hypertension (PPH) a rare but frequently fatal illness of young adults. Increased blood pressure in the pulmonary circulation leads to right-heart failure. Continuous infusion of epoprostanol leads to a decrease in blood pressure however, it is unclear whether this is due to direct dilator activity of the IP receptor acting on smooth muscle, or a more indirect mechanism. 

The onset of symptoms of barbiturate toxicity may not occur until several hours after the drug is administered. Symptoms of acute toxicity include CNSand respiratory depression, constriction or paralytic dilation of the pupils tachycardia, hypotension, lowered body temperature, oliguria, circulatory collapse, and coma. The nurse should report any symptoms of toxicity to the primary health care provider immediately. 

A broncho dilator is a drug used to relieve bron-chospasm associated with respiratory disorders, such as bronchial asthma, chronic bronchitis, and emphysema These conditions are progressive disorders characterized by a decrease in die inspiratory and expiratory capacity of die lung. Collectively, tiiey are often referred to as COPD. The patient with COPD experiences dyspnea (difficulty breatiiing) with physical exertion, has difficulty inhaling and exhaling, and may exhibit a chronic cough. 

Diseases of the arteries can cause serious problems, namely coronary artery disease, cerebral vascular disease, and peripheral vascular disease Drug therapy for vascular diseases may include dragp that dilate blood vessels and thereby increase blood supply to an area... 

Systemic and coronary arteries are influenced by movement of calcium across cell membranes of vascular smooth muscle. The contractions of cardiac and vascular smooth muscle depend on movement of extracellular calcium ions into these walls through specific ion channels. Calcium channel blockers, such as amlodipine (Norvasc), diltiazem (Cardizem), nicardipine (Cardene), nifedipine (Procardia), and verapamil (Calan), inhibit die movement of calcium ions across cell membranes. This results in less calcium available for the transmission of nerve impulses (Fig. 41-1). This drug action of the calcium channel blockers (also known as slow channel blockers) has several effects on die heart, including an effect on die smooth muscle of arteries and arterioles. These drug dilate coronary arteries and arterioles, which in turn deliver more oxygen to cardiac muscle. Dilation of peripheral arteries reduces die workload of die heart. The end effect of these drug is the same as that of die nitrates. 

FIGURE 41 -1. Calcium channel blockers inhibit the movement of caldum ions across the cell membrane. When calcium channels are blocked by drug molecules, musde contraction is decreased, causing the smooth musdes of the arteries and arterioles to dilate. 

The nitrate antianginal drug all have the same adverse reactions, although the intensify of some reactions may vary with the drug and the dose. A common adverse reaction seen with diese drug is headache, especially early in therapy. Hypotension, dizziness, vertigo, and weakness may also be associated with headache. Flushing caused by dilatation of small capillaries near the surface of the skin may also be seen. 

Adverse reactions associated with these drugs are variable Some of tire more common adverse reactions are listed in tire Summary Drag Table Peripheral Vasodilators and Miscellaneous Vasodilating Drags. Because these drugs dilate peripheral arteries, some degree of hypotension may be associated with their... 

Many antihypertensive drug lower the blood pressure by dilating or increasing the size of the arterial blood vessels (vasodilatation). Vasodilatation creates an increase in the lumen (the space or opening within an arteiy) of the arterial blood vessels, which in turn increases the amount of space available for the blood to circulate Because blood volume (the amount of blood) remains relatively constant, an increase in the space in which the blood circulates (ie, the blood vessels) lowers the pressure of the fluid (measured as blood pressure) in the blood vessels. Although the method by which anti-hypertensive drug dilate blood vessels varies, the result... 

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