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Ondansetron: Pharmacokinetics & Drug Interactions

Instructor: Alyssa Campbell

Alyssa is an active RN and teaches Nursing and Leadership university courses. She also has a Doctorate in Nursing Practice and a Master's in Business Administration.

Ondansetron is particularly helpful in treating and preventing nausea. Read this lesson to learn how ondansetron is absorbed and broken down in the body, as well as its potentially life-threatening interactions with other medications.

Medicating for Nausea

Saul, a medical resident on a hospital rotation, is shadowing a senior doctor on a medical floor. The pair work closely throughout the day discussing patient cases, cutting-edge procedures, and the use of various medications. By mid-morning, Saul is comfortable working along with the senior resident and asks many questions to broaden his knowledge.

While preparing to assess their next patient, a 72-year-old man undergoing chemotherapy treatment for cancer, they speak with the nurse outside of the room. The nurse explains that the patient has been experiencing nausea, or stomach upset and discomfort, resulting in several episodes of vomiting. Saul and the resident both agree that ondansetron, a serotonin receptor antagonist, may need to be prescribed to treat the man's stomach upset.

Ordering Ondansetron

Ondansetron, a powerful antiemetic, is known for its abilities to decrease symptoms of nausea and prevent vomiting. Using this drug helps people maintain a healthy water balance and remain hydrated all while improving their comfort level and decreasing stomach upset. Ondansetron is usually ordered for individuals who:

  • Are taking chemotherapy, powerful cancer fighting drugs
  • Have undergone recent surgery
  • Are exposed to radiation, high levels of energy meant to target cancer tumors
  • Experience unresolving nausea

This medication works by effectively blocking a specific receptor located on the nerves of the gastrointestinal system, more specifically the stomach, to inhibit the intake of serotonin. Serotonin is a powerful chemical produced by the body that is linked to causing nausea and upset stomach.

Pharmacokinetics: What to Know About the Drug

Before ordering ondansetron for their patient suffering from nausea, the senior doctor prompts Saul to consider researching the pharmacokinetics of the drug prior to prescribing it. In doing so, Saul learns some important information regarding how the drug is processed by the body.

Absorption

There are several options for Saul to consider when ordering ondansetron for his patient. First, he must choose what form of the drug to prescribe. When he researches absorption, or how well the body takes the drug in, he finds that ondansetron in pill form is absorbed well. When any drug is ingested, some of the pill's materials are eliminated by the body. In the case of ondansetron, about 56% of the drug is available for use.

Potential for Toxicity

Saul also learns that ondansetron is largely processed by the liver, an organ in the body responsible for many metabolic processes and is important in preparing waste for elimination. This means if the liver is damaged, not working well, or is overburdened by breaking down other drugs, perhaps ondansetron should not be ordered. Fortunately, the liver function in Saul's patient is normal, enabling ondansetron to be ordered.

Drug Interactions

Knowing that he is likely to encounter patients with complications, Saul's mentoring doctor pushes him a step further to find drugs that cause dangerous interactions with ondansetron. Medications that particularly should not be used in conjunction with ondansetron include:

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