20.11d Medications Used to Treat Emesis

Emesis

(?) is a complex process that involves different parts of the brain, as well as receptors and muscles in the stomach and inner ear.

vomiting center

The two involved parts of the brain include the (?) in the medulla and the chemoreceptor trigger zone (CTZ).

directly

The vomiting center stimulates vomiting (?) whereas the CTZ does so indirectly.

H1

The vomiting center is stimulated by (?) and ACh receptors in the pathway between itself and the inner ear, by sensory input from the eyes and nose (unpleasant or disturbing sights and smells), and by other parts of the brain in response to anxiety or fear.

serotonin receptors

The CTZ stimulates the vomiting center in response to stimuli from (?) in the stomach and bloodborne substances such as opioids and ipecac.

Stimulating emesis

(?) is seldom desired, but it can be useful in treating certain types of overdoses or poisonings.

Ipecac

(?) is the medication of choice when stimulating emesis is indicated.

CTZ

It stimulates the (?) which, in turn, stimulates the vomiting center.

preventing emesis

Unlike causing emesis, (?) is frequently desirable.

Antiemetics

(?) are indicated in conjunction with chemotherapy, which can cause violent nausea and vomiting.

motion sickness

Antiemetics are also indicated in the prophylactic treatment of (?).

Multiple transmitters

(?) are involved in the vomiting reflex.

serotonin

They include (?), dopamine, acetylcholine, and histamine.

decrease or prevent nausea and vomiting

Medications that interfere with any of these transmitters can (?).

serotonin antagonists

This functional class includes several pharmacologic subclasses: (?), dopamine antagonists, anti-cholinergics, and cannabinoids.

ondansetron (Zofran)

The prototype serotonin antagonist is (?).

serotonin receptors

It blocks the (?) in the CTZ, the stomach, and the small intestine.

extrapyramidal effects

It is very effective in the treatment of nausea and vomiting associated with chemotherapy, and, unlike the dopamine antagonists, it does not cause (?) such as dystonia and ataxia.

headache

Its most common side effects are (?) and diarrhea.

dopamine receptors

Both phenothiazines and butyrophenones effectively block (?) in the CTZ.

prochlorperazine (Compazine)

(This chapter’s section on psychotherapeutic medications discusses both of these medications at length.) The phenothiazines include (?) and promethazine (Phenergan) whereas the butyrophenones include haloperidol (Haldol) and droperidol (Inapsine).

extrapyramidal effects

Agents from both classes cause side effects of (?) and sedation.

metoclopramide (Reglan)

Another dopamine antagonist, (?), is neither a phenothiazine nor a butyrophenone.

serotonin and dopamine receptors

It is unique in that it blocks both (?) in the CTZ.

Table 20-25

(?) details common antiemetics.

cannabinoids

The (?) are derivatives of tetrahydrocannabinol (THC) and are effective antiemetics used to treat chemotherapy-induced nausea and vomiting.

dronabinol (Marinol)

The two available agents are (?) and nabilone (Cesamet).

THC

Because both agents are essentially the same as (?) (the active ingredient in marijuana), their side effects include euphoria similar to that of marijuana.

intensely unpleasant

While those effects can be desirable for some, they can be (? ) for others.