Antiemetics: Nursing pharmacology

Antiemetics are a group of medications that are used to treat nausea and vomiting. These include ondansetron, metoclopramide, aprepitant, prochlorperazine, and promethazine, as well as antihistamines like diphenhydramine, and cannabinoids, such as dronabinol.

Let’s start with ondansetron, which can be administered orally, intravenously, and intramuscularly. Once administered, ondansetron acts as a 5-HT3 receptor antagonist peripherally by decreasing vagal nerve stimulation, but it is also a very powerful central acting antiemetic blocking an area in the brain called chemoreceptor trigger zone, or CTZ for short.

Ondansetron is primarily used to control nausea and vomiting after surgical anesthesia, as well in individuals undergoing chemotherapy or radiotherapy.

Next, metoclopramide can be administered orally, intranasally, intravenously, and intramuscularly, and subcutaneously. Once administered, it acts by blocking dopamine receptors in the CTZ.

As a result, the levels of dopamine decrease, preventing nausea and vomiting after surgical anesthesia as well as chemotherapy-induced nausea and vomiting.

Okay, another antiemetic is aprepitant, which can be given orally, as well as intravenously in the form of fosaprepitant. Once administered, it acts as a neurokinin receptor antagonist that blocks neurokinin-1, or NK-1, receptors in the CTZ, and thus, it can be used to prevent chemotherapy-induced nausea and vomiting.

Alright, moving onto prochlorperazine, which is a phenothiazine, and can be given orally, rectally, intravenously, and intramuscularly. Phenothiazines block dopamine receptors in the CNS and they’re mostly used as antipsychotics.