A client with a diagnosis of cancer is scheduled for chemotherapy. The nurse anticipates administering which of the following medications, 30-60 minutes prior to chemotherapy treatment?

A. Diabetes mellitus.: Timolol, a non-selective beta-blocker, can mask symptoms of hypoglycemia such as tachycardia, but it is not absolutely contraindicated in diabetes. Diabetic clients require close monitoring, the medication can still be used with caution.

B. Chronic kidney disease.: Timolol is administered topically as eye drops and has minimal systemic absorption, so it does not worsen kidney function. It is generally considered safe for clients with chronic kidney disease when used as prescribed.

C. Asthma.: Timolol can cause bronchoconstriction by blocking beta-2 receptors in the lungs, leading to respiratory distress in clients with asthma or COPD. Because of this risk, it is contraindicated in these patients, as even topical administration may trigger bronchospasm.

D. Hyperthyroidism.: Timolol may help manage some symptoms of hyperthyroidism, such as tremors or tachycardia, due to its beta-blocking effects. Therefore, it can be beneficial in controlling adrenergic symptoms in these clients.

A. Scopolamine.: Scopolamine is an anticholinergic primarily used to prevent motion sickness or postoperative nausea related to anesthesia. It is not the preferred agent for chemotherapy-induced nausea and vomiting because it does not target serotonin receptors involved in chemotherapy-related emesis.

B. Metoclopramide.: Metoclopramide is a prokinetic and antiemetic that enhances gastric motility and is sometimes used for mild to moderate nausea. However, it is less effective against the severe nausea caused by chemotherapy and may cause extrapyramidal side effects

C. Methylcellulose.: Methylcellulose is a bulk-forming laxative used to treat constipation by increasing stool volume and water content. It has no antiemetic properties and would not be useful in preventing chemotherapy-related nausea or vomiting.

D. Ondansetron.: Ondansetron is a serotonin 5-HT3 receptor antagonist that effectively prevents chemotherapy-induced nausea and vomiting. Administering it 30–60 minutes before treatment blocks serotonin release from the gastrointestinal tract, reducing nausea severity.