Contrast agent

Contrast Media: A Pharmacist’s Perspective Peggy Bickham, PharmD I have no actual or potential conflict of interest in relation to this program Objectives z List three classes of contrast agents and the imaging procedures for which they are used z Explain how each class of contrast agent functions to enhance the image that is produced z Describe how to manage risk of adverse events for each of the classes of contrast agents z Describe areas in which pharmacist involvement can impact positively on medication safety as it relates to contrast media Iodinated Contrast: CT and Fluoroscopy Contrast Agents CT and Fluoroscopy z Both use x-rays to generate images of internal structures z CT generates “slices” or a 3-D image from a series of 2-D images taken around an axis of rotation z Fluoroscopy generates real-time images of functioning internal structures; used in surgery and interventional procedures How Does Iodinated Contrast Media Work? z Iodine’s high atomic weight allows it to block the x-ray z Area appears white on the x-ray film z Provides contrast with surrounding tissues z Barium also blocks the x-ray; may be used as oral preparation prior to pelvic or abdominal CT scans to delineate the GI tract Angiogram: ContrastEnhanced Fluoroscopic Image CT Pre and Post-Contrast: Brain Metastases Fluoroscopy: Angiogram of Left Internal Carotid CT Pre and Post: Neurofibromatosis Contrast Agents High Osmolar (HOCM) About 900 – 2000 mOsm/L z Diatrizoate meglumine or sodium (Hypaque, Renografin) z Iothalamate meglumine (Conray) Low Osmolar (LOCM) About 500 – 850 mOsm/L z Ioxaglate (Hexabrix) z Ioxilan (Oxilan) z Ioversol (Optiray) z Iopromide (Ultravist) z Iopamidol (Isovue) z Iohexol (Omnipaque) Iso-Osmolar (IOCM) 290 mOsm/L z Iodixanol (Visipaque) High Osmolar Agents z First agents introduced in 1950’s z All HOCM are ionic z Higher incidence of adverse effects: 12.6% in ionic agents vs 3.1% in nonionic CM z High osmolarity can cause fluid shifts z Alteration in blood cell morphology, possible problem in sickle cell patients Low Osmolar Agents z Introduced in mid-1980’s through 1990’s z All but one LOCM are non-ionic z Lower incidence of adverse effects, including allergic reactions and CIN z Less pain on injection z Fewer injection site reactions z Less fluid shifting Characteristics of Low- and Iso-Osmolar CM Product Brand Name Ionic yes/no Osmolality (mOsm/kg) Viscosity 20o* Or 25oC (cps) Viscosity 37oC (cps) Structure Iohexol Omnipaque 300 No 672 11.8* 6.3 Monomer 350 No 844 20.4* 10.4 Monomer 300 No 616 8.8* 4.7 Monomer 370 No 796 20.9* 9.4 Monomer 300 No 607 9.2* 4.9 Monomer 370 No 774 22.0* 10 Monomer Iopamidol Iopromide Isovue Ultravist Conc Mg I/ml Ioversol Optiray 320 No 702 9.9 5.8 Monomer Ioxaglate Hexabrix 320 Yes 600 15.7* 7.5 Monomer Ioxilan Oxilan 300 No 585 9.4* 5.1 Monomer Iodixanol Visipaque 320 No 290 26.6 11.8 Dimer Dosing and Administration z Volumes used are variable and depend on requirements of imaging procedure z CT scans typically use lower volumes z Fluoroscopy during procedures have potential to use high volumes, depending on the length of the procedure z Many routes: IV, intra-articular, intraarterial, oral, rectal, others Clearance z Excreted by glomerular filtration z Hemodialysis effective at removing z Peritoneal dialysis slower than hemodialysis, but also effective z Hemofiltration effective as well z Recommended to schedule CT just before dialysis Contrast Induced Nephropathy (CIN) z Increase in SCr of 25% or of greater than 0.5mg/dL within 24 hours after contrast administration z Peak within 48-72 hours, usually return to baseline within 10 days z Kidneys usually recover, but some patients never recover to baseline or require dialysis z Causes not well understood; possibly direct toxic effect on renal tubules and ischemic injury mediated by reactive oxygen species Patient Risk Factors for CIN z Poor kidney function (SCr >1.5 or GFR