A nurse is completing a medication history for a client who reports using over-the-counter calcium carbonate antacid. Which of the following recommendations should the nurse make about taking this medication?

Choice A reason: Peak level is the correct term to describe the highest concentration of a drug in the blood after it is administered. Peak level is also known as peak plasma concentration or Cmax, and it reflects the rate and extent of drug absorption. Peak level is influenced by factors such as the route of administration, the dose, the formulation, and the bioavailability of the drug. Peak level is important to monitor for drugs that have a narrow therapeutic range, meaning that there is a small difference between the effective and toxic doses. The nurse should measure the peak level at the appropriate time after the drug administration, and adjust the dose or the frequency as needed to achieve the desired therapeutic effect and avoid adverse effects .

Choice B reason: Halflife is not the correct term to describe the highest concentration of a drug in the blood after it is administered. Halflife is the time it takes for the concentration of a drug in the blood to decrease by 50%. Halflife reflects the rate of drug elimination, which depends on factors such as the metabolism and excretion of the drug. Halflife is important to determine the dosing interval and the time to reach steady state. The nurse should consider the halflife of the drug when prescribing or administering the drug, and avoid drug accumulation or subtherapeutic levels .

Choice C reason: Trough level is not the correct term to describe the highest concentration of a drug in the blood after it is administered. Trough level is the lowest concentration of a drug in the blood before the next dose is given. Trough level reflects the balance between drug absorption and elimination, and it indicates the minimum effective concentration of the drug. Trough level is important to monitor for drugs that have a narrow therapeutic range, meaning that there is a small difference between the effective and toxic doses. The nurse should measure the trough level just before the next dose of the drug, and adjust the dose or the frequency as needed to achieve the desired therapeutic effect and avoid adverse effects .

Choice D reason: Steady state is not the correct term to describe the highest concentration of a drug in the blood after it is administered. Steady state is the condition when the rate of drug administration is equal to the rate of drug elimination, and the concentration of the drug in the blood remains constant. Steady state is usually reached after four to five halflives of the drug, and it reflects the optimal therapeutic level of the drug. Steady state is important to maintain for drugs that have a long halflife or a narrow therapeutic range, meaning that there is a small difference between the effective and toxic doses. The nurse should ensure that the drug is administered at regular intervals and at the appropriate dose to achieve and maintain steady state.

Choice A reason: “This medication should be taken after eating to reduce nausea.” is not a correct statement that demonstrates understanding about ondansetron. Ondansetron is a medication that prevents nausea and vomiting by blocking the action of serotonin, a chemical that stimulates the vomiting center in the brain. Ondansetron can be taken with or without food, and it does not affect the digestion or absorption of food. Ondansetron is usually taken before the start of chemotherapy, radiation, or surgery, which are the common causes of nausea and vomiting.

Choice B reason: “This medication should not be taken with starfruit.” is not a correct statement that demonstrates understanding about ondansetron. Ondansetron is a medication that prevents nausea and vomiting by blocking the action of serotonin, a chemical that stimulates the vomiting center in the brain. Ondansetron does not interact with starfruit, which is a tropical fruit that contains substances that can inhibit the enzyme CYP3A4, which is involved in the metabolism of many drugs. Ondansetron is mainly metabolized by another enzyme, CYP1A2, and it has a low potential for drug interactions¹.

Choice C reason: “This medication may make me tired and confused.” is a correct statement that demonstrates understanding about ondansetron. Ondansetron is a medication that prevents nausea and vomiting by blocking the action of serotonin, a chemical that stimulates the vomiting center in the brain. Ondansetron can also cross the blood brain barrier and affect other serotonin receptors in the brain, which are involved in regulating mood, cognition, and sleep. Ondansetron can cause side effects such as fatigue, drowsiness, headache, and confusion, which can impair the mental alertness and performance of the client. The client should be advised to avoid driving, operating machinery, or doing other tasks that require attention after taking ondansetron.

Choice D reason: “This medication may cause rebound nausea.” is not a correct statement that demonstrates understanding about ondansetron. Ondansetron is a medication that prevents nausea and vomiting by blocking the action of serotonin, a chemical that stimulates the vomiting center in the brain. Ondansetron does not cause rebound nausea, which is a condition of nausea that occurs after the discontinuation of a medication that suppresses nausea. Ondansetron is not a medication that suppresses nausea, but rather prevents it by blocking the stimulation of the vomiting center. Ondansetron does not cause dependence or withdrawal symptoms, and it can be stopped without causing rebound nausea.