Mechanism of Action Flashcards
Drug Quiz #2
Neostigmine (Bloxiverz)
Inhibits destruction of acetylcholine by acetylcholinesterase which facilitates transmission of impulses across myoneural junction; direct cholinomimetic effect on skeletal muscle and possible on autonomic ganglion cells and neurons of the CNS
Phenylephrine (Sudafed, Niorphen, Immphentiv, Medi-Phenyl, Vazculep
Potent, direct-acting alpha-adrenergic agonist with virtually no beta-adrenergic activity; produces systemic arterial vasoconstriction. Such increases in systemic vascular resistance may result in dose-dependent increases in systolic and diastolic blood pressure and reductions in heart rate and cardiac output (most noticeable in patients with preexisting cardiac dysfunction).
Hydralazine (Apresoline)
Direct vasodilation of arterioles (with little effect on veins) with decreased systemic resistance. Although exact mechanism unknown, arterial vasodilation may occur via inhibition of calcium release from the sarcoplasmic reticulum and inhibition of myosin phosphorylation in arterial smooth muscle cells.
Bupivacaine (Sensorcaine, Xaracol)
Blocks both the initiation and conduction of nerve impulses by decreasing the neuronal membrane’s permeability to sodium ions, which results in inhibition of depolarization with resultant blockade of conduction
Atracurium (Tracurium)
Blocks neural transmission at the myoneural junction by binding with cholinergic receptor sites
Oxytocin (Pitocin)
Stimulates uterine contractions by acting on receptors that trigger the release of intracellular calcium and local prostaglandin production. Oxytocin specific receptors are not present in the uterus until ~13 weeks’ gestation and increase as pregnancy progresses and reach maximum concentration at term. Therefore, term pregnancies are more sensitive to lower oxytocin doses. The action of oxytocin is limited by the concentration of receptors in the smooth muscle of the uterus. Repeated doses may cause desensitization of the receptors and decreased response.
Methylergonovine (Methergine)
Increases the tone, rate and amplitude of contractions on the smooth muscles of the uterus, producing sustained contractions which shortens the third stage of labor and reduces blood loss.
Esmolol (Brevibloc)
Competitively blocks response to beta1-adrenergic stimulation with little or no effect of beta2-receptors except at high doses, no intrinsic sympathomimetic activity, no membrane stabilizing activity
Adenosine (Adenocard)
Antiarrhythmic actions: Slows conduction time through the AV node, interrupting the re-entry pathways through the AV node, restoring normal sinus rhythm. Myocardial perfusion scintigraphy: Adenosine also causes coronary vasodilation and increases blood flow in normal coronary arteries with little to no increase in stenotic coronary arteries; thallium-201 uptake into the stenotic coronary arteries will be less than that of normal coronary arteries revealing areas of insufficient blood flow.
Isoproterenol (Isuprel)
Stimulates beta1- and beta2-receptors resulting in relaxation of bronchial, GI, and uterine smooth muscle, increased heart rate and contractility, vasodilation of peripheral vasculature
Antithrombin 3 (Thrombate iII)
Antithrombin is the primary physiologic inhibitor of in vivo coagulation. It is an alpha2-globulin. Its principal actions are the inactivation of thrombin, plasmin, and other active serine proteases of coagulation, including factors IXa, Xa, XIa, and XIIa. The inactivation of proteases is a major step in the normal clotting process. The strong activation of clotting enzymes at the site of every bleeding injury facilitates fibrin formation and maintains normal hemostasis. Thrombosis in the circulation would be caused by active serine proteases if they were not inhibited by antithrombin after the localized clotting process
