Drug Quiz #4: Mechanism of Action

Question 1

Sugammadex (Bridion)

Answer 1

A modified gamma cyclodextrin which is a selective relaxant binding agent. It forms a complex with the neuromuscular-blocking agents rocuronium or vecuronium in plasma, reducing the amount of neuromuscular-blocking agent available to bind to nicotinic receptors in the neuromuscular junction. This results in the reversal of neuromuscular blockade induced by rocuronium or vecuronium.

Question 2

Prothrombin Complex Concentrate (Human) [(Factors II, VII, IX, X), Protein C, and Protein S (Kcentra, Balfaxar)

Answer 2

Provides an increase in the levels of the vitamin K-dependent coagulation factors (II, VII, IX, and X) with the addition of protein C and protein S. Coagulation factors II, IX, and X are part of the intrinsic coagulation pathway, while factor VII is part of the extrinsic coagulation pathway. In the extrinsic pathway, damaged blood vessels release endothelial tissue factor (TF) which complexes with factor VII to form TF-factor VIIa. Within the intrinsic pathway, factor IX is converted to IXa. Factor IXa (as well as TF-factor VIIa) converts factor X to factor Xa in the final common pathway of coagulation.

Question 3

Bupivacaine (Liposomal) (Exparel)

Answer 3

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.

Question 4

Dexmedetomidine (Precedex)

Answer 4

Selective alpha2-adrenoceptor agonist with anesthetic and sedative properties thought to be due to activation of G-proteins by alpha2a-adrenoceptors in the brainstem resulting in inhibition of norepinephrine release; peripheral alpha2b-adrenoceptors are activated at high doses or with rapid IV administration resulting in vasoconstriction.

Question 5

Abciximab (Reopro)

Answer 5

A chimeric human-murine monoclonal antibody Fab (fragment antigen binding) fragment. It inhibits platelet aggregation by specifically binding to the glycoprotein GPIIb/IIIa receptor, the major surface receptor involved in the final common pathway for platelet aggregation. Abciximab binding to the GPIIb/IIIa receptor prevents fibrinogen, von Willebrand factor, vitronectin, and other adhesive molecules from binding to the receptor, thereby inhibiting platelet aggregation.

Question 6

Tirofiban (Aggrastat)

Answer 6

A reversible antagonist of fibrinogen binding to the glycoprotein (GP) IIb/IIIa receptor, the major platelet surface receptor involved in platelet aggregation. When administered intravenously, it inhibits ex vivo platelet aggregation in a dose- and concentration-dependent manner. When given according to the recommended regimen, >90% inhibition is attained within 10 minutes after initiation. Platelet aggregation inhibition is reversible following cessation of the infusion.

Question 7

Cocaine (C-Topical, Goprelto, Numbrino)

Answer 7

Ester local anesthetic 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; interferes with the uptake of norepinephrine by adrenergic nerve terminals producing vasoconstriction

Question 8

Mannitol (Osmitrol, Resectisol)

Answer 8

Produces an osmotic diuresis by increasing the osmotic pressure of glomerular filtrate, which inhibits tubular reabsorption of water and electrolytes and increases urinary output . Mechanism of action in reduction of intracranial pressure (ICP) is less clear. However, it is thought that mannitol reduces ICP by reducing blood viscosity which transiently increases cerebral blood flow and oxygen transport and constricts pial arterioles. This in turn reduces cerebral blood volume and ICP. Furthermore, mannitol reduces ICP by withdrawing water from the brain parenchyma and excretes water in the urine

Question 9

Tranexamic Acid (Cyklokapron; Lysteda)

Answer 9

Forms a reversible complex that displaces plasminogen from fibrin resulting in inhibition of fibrinolysis; it also inhibits the proteolytic activity of plasmin. With reduction in plasmin activity, tranexamic acid also reduces activation of complement and consumption of C1 esterase inhibitor (C1-INH), thereby decreasing inflammation associated with hereditary angioedema.

Question 10

Ketamine (Ketalar)

Answer 10

Produces a cataleptic-like state in which the patient is dissociated from the surrounding environment by direct action on the cortex and limbic system. Ketamine is a noncompetitive NMDA receptor antagonist that blocks glutamate. Low (subanesthetic) doses produce analgesia, and modulate central sensitization, hyperalgesia and opioid tolerance. Reduces polysynaptic spinal reflexes.