Gadopentetic acid
Gd- DTPA
V08CA01
Paramagnetic contrast agents
9411 mg · kg -1 ( LD50, rat, i.v.)
Template: Infobox chemical / molecular formula search available
Gadopentetate dimeglumine is a drug which is used as contrast agents in magnetic resonance imaging ( MRI). It is the dimeglumine salt of gadopentetic (Gd - DTPA). The gadolinium ions contained enhance the contrast in imaging.
Structure and operating principle of the contrast agent
Gadopentetic is a chelate complex of a gadolinium ion and the complexing agent diethylene triamine pentaacetic acid ( DTPA). The complex is extremely rigid and very stable, because free, not complexed gadolinium ions are toxic for human and most animal organisms. The stability constant of DTPA is, at a pH value of 7, above 1020.
Gadolinium has on the outer -shell (f- shell ) seven unpaired electrons, which gives the element a strong paramagnetism. Protons, as they occur in the water of body fluids such as, relax much more rapidly near to gadolinium. In particular, the so-called T1 - time is significantly reduced by gadolinium. Areas in which the contrast agent accumulates, are therefore presented in T1 - weighted images brighter than other structures. Thus, the image quality of a MRI scan is significantly improved.
As a highly polar and relatively large molecule gadopentetic can not be overcome in a healthy person in a position the blood- brain barrier after it was administered intravenously. However, in some diseases, such as in a glioblastoma, it can overcome the damaged blood -brain barrier and penetrate into the affected tissue. Thus, it is possible a more precise information on the nature and location of the tumor to win. Also, the tumor in the imaging borders better off compared to the healthy tissue. The effect of overcoming the blood -brain barrier is an important diagnostic method for brain tumors.
In the joint diagnostics gadopentetate dimeglumine is administered in the interior of joint ( intra-articular ).
Gadopentetic diffuses after intraarticular administration quickly into the blood and the extracellular space. From there it is almost completely excreted by the kidney, the half-life is approximately 1.5 hours.
Side effects
Gadopentetate dimeglumine is very well tolerated. Allergic reactions occur rarely or allergiforme ( at 0.1 to 0.01 percent of the patients) on. In patients with kidney dysfunction may nephrogenic systemic fibrosis are triggered. In such patients should be apart of a contrast agent.
History of development
The diagnostic agent gadopentetate dimeglumine was developed in 1984 with Schering AG in 1988 and approved under the name Magnevist ® as a first contrast agent for magnetic resonance imaging. Although there are now a wide variety of approved modifications ( both the DTPA itself, as well as totally different gadolinium chelators ), it is still the most commonly used contrast agents in MRI. Approx. 40 to 50 % of all magnetic resonance images in Germany are performed with gadopentetate dimeglumine.
From 1984 to 2005, the agent was applied nearly 60 million copies worldwide. Schering AG achieved in 2005 with a turnover of over 300 million euros.
Since patent expiry in late 2007 cheaper generics were introduced.