Drug General Information (ID: DDIYP621U5)
Drug Name			Guanethidine		Drug Info		Iobenguane (I-131)		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Antihypertensive Agents				Therapeutic Radiopharmaceuticals
Structure

Mechanism of Guanethidine-Iobenguane (I-131) Interaction (Severity Level: Major)
Interference of cell/tissue uptake Click to Show/Hide Mechanism Graph
Drug Name		Guanethidine				Iobenguane (I-131)
Mechanism		Interference with radiolabeled norepinephrine analog effects				Radiolabeled norepinephrine analog
Key Mechanism Factor 1
		Factor Name		Pharmacokinetics
		Factor Description		Alters the distribution of the drug, leading to changes in the plasma concentration of the drug and affecting the pharmacological effects.
Mechanism Description		Interference of cell/tissue uptake of Iobenguane (I-131) by Guanethidine

Recommended Action
Management		Drugs that reduce catecholamine uptake or deplete catecholamine stores should be discontinued for at least five biological half-lives before administration of either the dosimetry dose or a therapeutic dose of iobenguane I-131. Do not administer these drugs until at least 7 days after each iobenguane I-131 dose. Patients should be monitored for the occurrence of clinically significant withdrawal symptoms, especially patients with elevated levels of circulating catecholamines and their metabolites.

References
1	Product Information. Azedra (iobenguane I-131). Progenics Pharmaceuticals, Inc., New York, NY.