Pharmacology: Chapter 33

A 21-year-old pregnant woman comes into the clinic complaining of extreme "morning sickness." She has not been able to keep down any food or drink for 2 days. The nurse understands that these treatments are available. (Select all that apply.) 1. Hospitalization with management of fluids and electrolytes by the IV route 2. NPO until the nausea and vomiting passes 3. Antihistamines such as diphenhydramine 4. Ginger (herb) to treat the nausea and vomiting 5. Scopolamine transdermal patch

1. Hospitalization with management of fluids and electrolytes by the IV route 3. Antihistamines such as diphenhydramine 4. Ginger (herb) to treat the nausea and vomiting *Treatments for pregnant women with morning sickness include: hospitalization with IV fluids and electrolytes, and nutritional therapy if the vomiting is persistent and severe and interferes with nutrition, fluid, and electrolyte balance. The women may have hyperemesis gravidarum, a condition in which starvation, dehydration, and acidosis are superimposed on the vomiting syndrome. Drugs such as vitamin B6, antihistamines (doxylamine, diphenhydramine, dimenhydrinate, meclizine), and phenothiazines such as promethazine and prochlorperazine may be used. Also, the herb ginger (see Chapter 47) is used in many cultures to treat pregnancy-induced nausea and vomiting. Vitamin B6 and doxylamine are generally recommended first.*

The nurse was discussing with a patient different ways to deal with anticipatory nausea and vomiting and included in the discussion the following: (Select all that apply.) 1. "We generally administer antiemetic drugs as soon as nausea develops, as this will adequately control your symptoms." 2. "You can expect that anticipatory nausea to become more severe as your chemotherapy treatments progress." 3. We can teach you nonpharmacologic management of your nausea that includes progressive muscle relaxation and self-hypnosis." 4. "It is recommended that we use antiemetic therapy prior to chemotherapy so that the nausea does not occur." 5. "The triggers for this type of nausea are often brushing teeth, seeing food, or standing up too quickly."

2. "You can expect that anticipatory nausea to become more severe as your chemotherapy treatments progress." 3. We can teach you nonpharmacologic management of your nausea that includes progressive muscle relaxation and self-hypnosis." 4. "It is recommended that we use antiemetic therapy prior to chemotherapy so that the nausea does not occur." *Anticipatory nausea and vomiting is a conditioned response triggered by the sight or smell of the clinic or hospital or by the knowledge that treatment is imminent. The onset of this response is usually 2-4 hours before treatment and is most severe at the time of chemotherapy administration. Some treatments for this conditioned response include progressive muscle relaxation, guided imagery, hypnosis, self-hypnosis, systematic desensitization, music therapy, and acupressure. Nurses need to make sure that patients receive antiemetic therapy before each course of chemotherapy. Brushing teeth, seeing food or standing up too quickly do not trigger this response. In order to be effective, antiemetic drugs must be administered before nausea symptoms develops and not wait until nausea begins.*

The patient with chemotherapy-induced nausea and vomiting was receiving benzodiazepines because these drugs will (Select all that apply.) 1. act through several mechanisms to inhibit pathways to the vomiting center (VC). 2. reduce anxiety associated with chemotherapy-induced nausea and vomiting. 3. be used to counterbalance the excessive amounts of acetylcholine believed to be present. 4. depress the VC. 5. inhibit dopamine receptors that are part of the pathway to the VC

2. reduce anxiety associated with chemotherapy-induced nausea and vomiting. 4. depress the VC. *Benzodiazepines used as an antiemetic for chemotherapy-induced nausea and vomiting reduce anxiety associated with chemotherapy-induced nausea and vomiting and depress the vomiting center (VC). They do not inhibit pathways to the VC. Antiemetic agents include dopamine antagonists, anticholinergic agents, and serotonin antagonists. They do not counterbalance the excessive amounts of acetylcholine or inhibit dopamine receptors in the pathway to the VC. These antiemetic agents work through a combination of effects including sedation and an amnesic effect. The amnesic effect appears to be most important in treating cancer patients, and in this respect, lorazepam and midazolam are superior to diazepam.*

The anticholinergic agents are used to prevent this type of nausea. 1. Anticipatory nausea and vomiting 2. Radiation-induced nausea and vomiting 3. Chemotherapy-induced nausea and vomiting 4. Motion sickness

4. Motion Sickness *Anticholinergic agents, such as scopolamine, and antihistamines (e.g., diphenhydramine, dimenhydrinate, cyclizine, meclizine, promethazine) are used to treat motion sickness and nausea and vomiting associated with pregnancy. Anticholinergic agents are also used to prevent postoperative nausea and vomiting.*

Chemotherapy Induced Nausea & Vomiting

Acute- within 1-6 hrs of treatment Delayed- from 12-24 hrs of treatment Anticipatory- anticipation of treatment causes N/V

Drug Therapy: Pregnancy

Diet is the *first option* in controlling morning sickness. -Ginger Antihistamines & Phenothiazines (a class of major tranquilizers) may be used.

Vomiting

Emesis. Ejection through the mouth of the gastric content. *Hyperemesis* can cause an electrolyte imbalance.

Vomiting Center

Located in medulla, coordinates vomiting reflex. Connected via Vagus & Splanchnic Nerves

Drug Therapy: Motion Sickness

Medications used are chemically similar to *antihistamines* & have anticholinergic properties. *can cause dehydration*

Drug Therapy: Psychogenic Vomiting

Metoclopramide or anti-anxiety drug may be prescribed. Diagnosis made when *all other causes of emesis are fulminated*

Psychogenic Vomiting

Self-Induced or Involuntary emesis in response to threatening or distasteful situations

Nausea

Sensation of abdominal discomfort intermittently accompanied by a desire to vomit.

Drug Therapy: Chemo. Induced

The medications should be used *prophylactically* - 30-60 mins. before chemo and continuously for 1-2 days afterward. Combinations of drugs are used because the emesis is caused by more than one mechanism.

Nursing Process: N&V

Upon Assessment: baseline vs, hydration status, and lab studies. Implementation: gradual progression of diet: stop solid foods>oral rehydration>NPO/NG tube if severe. -In infants, milk/solid foods should be discontinued and small volumes of liquids should be given every 30-60 mins. *Schedule anti-emetic drugs*

Regurgitation

Wretching/Dry Heaving Rising of gastric or esophageal contents to the pharynx as a result of stomach pressure

Drug Class: Neurokinin-1 Receptor Antagonists

aprepi*tant*, fosaprepi*tant*, rolapi*tant* *Blocks the effects of substance P, a neuropeptide in the CNS, responsible for vomiting* Prevents acute and delayed Chemo. Induced N&V *Side Effects*: tiredness, nausea, hiccups, constipation, diarrhea, loss of appetite, headache, hair loss. *numerous drug interactions*.

Drug Class: Anticholinergic Agents

cycli*zine*, diphenhydra*mine*, dimenhydra*nate* *Counterbalance excessive amounts of acetylcholine thought to cause motion sickness* Treat motion sickness & NV associated with pregnancy. *Side Effects*: sedative effects, anticholinergic effects (dry mouth, constipation, drowsiness, difficulty urinating/sweating)

Drug Class: Corticosteroids

dexametha*sone*, methylpredniso*lone* *Mechanism of action is unknown, but corticosteroids can increase mood, appetite, and sense of well being.* Used in combination with other anti-emetics to relieve N&V; can be used alone. *Side Effects*: increased risk of infections, hypertension, headache, loss of Potassium, muscle weakness, edema.

Drug Class: Serotonin Antagonists

dolase*tron*, granisetron, ondansetron, etc. *Block the serotonin 5-HT3 receptors located in the chemoreceptor trigger zone of the medulla and in specialized cells of the GI tract* Treat N&V associated with: chemo., radiation, & PONV. *Side Effects*: headache, diarrhea, constipation, sedation.

Drug Class: Cannabinoids

dronab*inol* (THC), nabilone *Inhibit pathways to the VC by several mechanisms* Used in patients refractory to other anti-emetic regimens, *only* for patients receiving chemotherapy. *Side Effects*: dysphoric effects.

Drug Class: Benzodiazepines

loraz*epam* *Enhance the effect of the neurotransmitter gamma-aminobutyric acid (GABA), resulting in sedative, hypnotic (sleep-inducing), anxiolytic (anti-anxiety), anticonvulsant, and muscle relaxant properties.* Used in combination with other anti-emetics to treat vomiting/nausea, and anxiety associated with chemotherapy. *Side Effects*: drowsiness, confusion, dizziness, blurred vision, weakness, slurred speech, lack of coordination, difficulty breathing.

Drug Class: Dopamine Antagonists

phentothiazines, butyrophenones, metoclopramide (Reglan). *Inhibit dopamine receptors that are part of the pathway to the vomiting center* Used as anti-emetics to treat mild>moderate nausea/vomiting associated with anesthesia, surgery, radiation therapy and cancer chemotherapy. *Side Effects*: orthostatic hypotension, sedation, drowsiness, tachycardia, agranulocytosis. -for injections: burning, stinging, or pain.