0071483446.pdf

(^278) CHAPTER 15 Nervous System Drugs
TOPICAL ANESTHETIC AGENTS
Topical anesthetic agents (see chart) are solutions, liquid sprays, ointments,
creams, and gels that are applied to mucous membranes, broken or unbroken
skin surfaces, and burns to decrease the sensitivity of nerve endings in the
affected area.
The first topical anesthetic agent was TAC, which is a combination of tetra-
caine, adrenaline (epinephrine), and cocaine, and was used for face and scalp
lacerations. A version of TAC called LET is used today. LET is a combination
of lidocaine, epinephrine, and tetracaine. Lidocaine replaced cocaine. LET gel is
Commonly administered intravenous anesthetic agents
Ketamine Affects the senses, and produces a dissociative anesthesia (catatonia,
(Ketalar) amnesia, analgesia) in which the patient may appear awake and
reactive, but cannot respond to sensory stimuli. These properties
make it especially useful in developing countries and during warfare
medical treatment. Ketamine is frequently used in pediatric patients
because anesthesia and analgesia can be achieved with an intramus-
cular injection. It is also used in high-risk geriatric patients and in
shock cases, because it also provides cardiac stimulation.
Thiopental A barbiturate that induces a rapid hypnotic state of short duration.
(Pentothal) Because thiopental is slowly metabolized by the liver, toxic
accumulation can occur; therefore, it should not be continuously
infused. Side effects include nausea and vomiting upon awakening.
Opioids Fentanyl, sufentanil, and alfentanil are frequently used prior to
anesthesia and surgery as a sedative and analgesic, as well as a
continuous infusion for primary anesthesia. Because opioids rarely
affect the cardiovascular system, they are particularly useful for
cardiac surgery and other high-risk cases. Opioids act directly on
spinal cord receptors, and are frequently used in epidurals for spinal
anesthesia. Side effects may include nausea and vomiting, itching,
and respiratory depression.
Propofol Nonbarbiturate hypnotic agent and the most recently developed
(Diprivan) intravenous anesthetic. Its rapid induction and short duration of
action are identical to thiopental, but recovery occurs more quickly
and with much less nausea and vomiting. Also, propofol is rapidly
metabolized in the liver and excreted in the urine, so it can be used
for long durations of anesthesia, unlike thiopental. Hence, propofol
is rapidly replacing thiopental as an anesthetic agent.