Respiratory system sympathomimetics

Mechanism of Action A sympathomimetic amine that produces CNS and respiratory stimulation, mydriasis, bronchodilation, a pressor response, and contraction of the urinary sphincter Directly effects alpha and beta receptor sites in peripheral system. Enhancesreleaseof norepinephrine by blocking reuptake, inhibiting monoamine oxidase. Therapeutic Effect Increases motor activity, mental alertness decreases drowsiness, fatigue. 

Stimulants are classic examples of sympathomimetic drugs that is, they act to stimulate or mimic activity in the sympathetic branch of the autonomic nervous system. Thus, many of their physiological effects arc the same as those seen during emotional arousal heart rate is up, blood pressure is up, respiratory rate is up, and sweating increases meanwhile, blood flow decreases to the internal organs and extremities but increases to the large muscle groups and the brain. Finally, body temperature is elevated and pupils arc dilated. 

Sympathomimetics mimic the action of noradrenaline (norepinephrine), the principal neurotransmitter between the nerve endings of the sympathetic nervous system and the adrenergic receptors of the innervated tissues. They stimulate both alpha-adrenoceptors, causing constriction of smooth muscle and blood vessels, and beta-adrenoceptors, producing bronchodilatation. They are therefore useful in coughs where the tissues of the upper respiratory tract are congested, as they shrink swollen mucosa and open up the airways. 

Central nervous system (CNS) stimulants are drugs that produce generalized stimulation of the brain or spinal cord which may lead to eonvulsion. They are of limited therapeutic value beeause of their convulsant activities. There are, however, some that are used as respiratory stimulants (e.g., Nikethamide) and others like the xanthine derivatives have many pharmacological actions and uses. Sympathomimetic amines like amphetamines and ephedrine, which are potent CNS stimulants, are discussed elsewhere. 

Systemic (Listed in Table 10.2)) Decrease inflammation and edema in respiratory tract. Enhance activity of sympathomimetics in hypoxic and acidotic states. Asthma which can not be controlled by sympathomimetics (bronchodilators) alone. Sodium/water retention and subsequent cardiovascular problems, weakness, osteoporosis, peptic ulcers. 

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