Comprehensive Nursing Pharmacology Q 164
Nurse Gretchen is discussing the use of cocaine as a local anesthetic with a nursing student. Which statement by the student indicates understanding of this agent?
A. "Anesthetic effects develop slowly and persist for several hours."
B. "Cocaine is a local anesthetic administered by injection."
C. "Vasoconstrictors should not be used as adjunct agents with this drug."
D. "When abused, cocaine causes physical dependence."
Correct Answer: C. “Vasoconstrictors should not be used as adjunct agents with this drug.”
Cocaine should not be combined with epinephrine or other vasoconstrictors, because it causes vasoconstriction itself, and the combination could precipitate severe hypertension. The principal action of cocaine on the mucosa is anesthesia and vasoconstriction, however significant systemic absorption may occur; this may adversely affect the cardiovascular system, after which alpha- and beta 1-adrenoceptor stimulation results in increased heart rate, systemic arterial pressure, and myocardial contractility, which are major determinants of myocardial oxygen demand.
Option A: Cocaine has a rapid onset of effects, which last about 1 hour. Cocaine and its metabolites may cause arterial vasoconstriction hours after use. Epicardial coronary arteries are especially vulnerable to these effects, leading to a decreased myocardial oxygen supply.
Option B: It is used only topically for anesthesia. Topical cocaine has an anesthetic effect similar to local anesthetics (such as lidocaine) from sodium channel blockade and interference with action potential propagation. This Vaughn-Williams class IC effect also increases the risk of conduction disturbance and tachyarrhythmias.
Option D: Although subject to widespread abuse with profound psychological dependence, it does not cause substantial physical dependence. The fatal dose of cocaine has been estimated to be 1.2 g, but there are reports of severe adverse effects from doses as low as 20 mg. The single-use vial contains four mL of a 40 mg/mL solution, thus 160 mg in total. There is also a multi-use vial containing 10 mL of 4% cocaine. As mucosal absorption is variable, the possibility of receiving the entire amount of cocaine is low, especially when delivered by cotton pledgets or gauze.