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DROPERIDOL

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mechanism of action
structure-activity relationship
pharmacokinetics
effects on organ systems
drug interactions

MECHANISM OF ACTION

Central effects:
-dopamine receptor antagonist
-interferes with serotonin, norepinephrine, and GABA transmission
-therefore leads to tranquilizing and antiemetic effects

Peripheral effects:
-alpha adrenergic blockade
-therefore may lead to decreased mean arterial pressure

STRUCTURE-ACTIVITY RELATIONSHIPS
-butyrophenone
-structurally related to haloperidol

PHARMACOKINETICS

Absorption
-usually give intravenously although may occasionally be given intramuscularly as a premedication regimine

Distribution
-rapid redistribution phase of 10 minutes
-delayed sedative effects due to relatively large molecular weight and extensive protein binding
-large molecular weight and extensive protein binding slows the pentration of the BBB
-prolonged duration of action due to strong receptor binding

Biotransformation
metabolized extensively in the liver
-rapid hepatic clearance

Excretion
-excreted primarily by the kidney into the urine

PHARMACODYNAMICS
Effects on Organ Systems

Central nervous system
-CMR02 not reduced unlike the effects of other induction agents (excluding ketamine)
-decreases CBF
-decreases ICP secondary to vasoconstriction of cerebral vasculature
-potent antiemetic activity
-delayed awakening therefore intraoperative use may be limited to small doses (ex. 0.05 mg/kg - 2.5 mg)
-may rarely precipitate extrapyramidal reactions (ex. oculogyric crises, torticollis)
-avoided in parkinsonian patients

Cardiovascular system
-decreases mean arterial pressure by peripheral vasodilation from mild alpha adrenergic blockade
-may have exaggerated hypotensive effects in hypovolemic patients
-antidysrhythmic effects possibly from alpha adrenergic blockade
-should be avoided inpatients with pheochromocytoma due to associated catecholamine release from the adrena medulla

Respiratory system
-when given alone at usuall doses: no significant ventilatory depression
-possibly may stimulate hypoxic ventilatory drive

Drug Interactions
-may preciptate parkinson symptoms
-may antagonize effects of levodopa