HYPAQUE SODIUM- diatrizoate meglumine injection, solution
Amersham Health Inc.
Sterile Aqueous Injection
For Excretory Urography
Contrast Enhancement of Computed Tomographic Head Imaging
|NOT FOR INTRATHECAL USE|
HYPAQUE meglumine, brand of diatrizoate meglumine, is a water-soluble, radiopaque diagnostic medium. It is a triiodinated benzoic acid derivative containing 47.06 percent organically bound iodine. It is constituted as an iodinated anion (diatrizoate) and a radiolucent cation (meglumine).
HYPAQUE meglumine 60 percent (w/v) is a sterile aqueous solution containing 60 g of the meglumine salt of diatrizoic acid per 100 mL of solution. The solution is a clear-colorless to pale yellow liquid, and the pH is adjusted between 6.5 and 7.7 with diatrizoic acid or meglumine solution. It is a relatively thermostable solution and may be autoclaved without harmful effects, although it should be protected from strong light. The 60 percent solution contains edetate calcium disodium 1:10,000 as a sequestering stabilizing agent. Each 1 mL contains approximately 282 mg of organically bound iodine. The viscosity of the solution is 6.17 cp at 25°C and 4.12 cp at 37°C.
It is hypertonic to blood with an osmolality of 1415 mosm/kg (determined by VPO). A 13 percent solution (w/v) is isotonic.
It is a colorless, microcrystalline solid which is readily soluble in water.
It is meglumine 3,5-diacetamido-2,4,6-triiodobenzoate (C11 H9 I3 N2 O4 • C7 H17 NO5 ) with a molecular weight of 809.13, and has the following structural formula:
Intravascular injection of a radiopaque diagnostic agent opacifies those vessels in the path of the flow of the contrast medium, permitting radiographic visualization of the internal structures of the human body until significant hemodilution occurs.
At physiologic pH, the water soluble contrast media are completely dissociated into a radiopaque anion and a solubilizing cation. While circulating in tissue fluids, the compound remains ionized. However, it is not metabolized but excreted unchanged in the urine, each diatrizoate molecule remaining “obligated” to its meglumine moiety.
Following intravenous injection, the radiopaque diagnostic agents are immediately diluted in the circulating plasma. Equilibrium is reached with the extracellular compartment at about 10 minutes. Hence, the plasma concentration at 10 minutes is closely related to the dose corrected to body size.
The pharmacokinetics of the intravenously administered radiopaque contrast media are usually best described by a two compartment model with a rapid alpha phase for drug distribution and a slow beta phase for drug elimination. In patients with normal renal function, the alpha and beta half-lives were respectively 30 minutes and 120 minutes for diatrizoate. But in patients with renal functional impairment, the elimination half-life for the beta phase can be prolonged up to several days.
Injectable radiopaque diagnostic agents are excreted either through the liver or through the kidneys. The two excretory pathways are not mutually exclusive, but the main route of excretion seems to be governed by the affinity of the contrast medium for serum albumin. From 0% to 10% of diatrizoate sodium is bound to serum protein.
Diatrizoate salts are excreted unchanged predominantly through the kidneys by glomerular filtration. The amount excreted by the kidney during any period of time is determined by the filtered load; ie, the product of plasma contrast media concentration and glomerular filtration rate. The plasma concentration is dependent upon the dose administered and the body size. The glomerular filtration rate varies with the body size, sex, age, circulatory dynamics, diuretic effect of the drug, and renal function. In patients with normal renal function the maximum urinary concentration of diatrizoate meglumine occurs within 10 minutes with 12 percent of the administered dose being excreted. The mean values of cumulative urinary excretion for diatrizoate meglumine expressed as percentage of administered dose are 38 percent at 60 minutes, 45 percent at 3 hours, and 94 to 100 percent at 24 hours.
Urinary excretion of contrast media is delayed in infants younger than 1 month and in patients with urinary tract obstruction. The urinary iodine concentration is higher with the sodium salt of diatrizoic acid than with the meglumine salt.
The liver and small intestine provide the major alternate route of excretion for diatrizoate. In patients free of severe renal disease, the fecal recovery is less than 2 percent of the administered dose. In patients with severe renal impairment the excretion of these contrast media through the gallbladder and into the small intestine sharply increases; up to 20 percent of the administered dose has been recovered in the feces in 48 hours.
Saliva is a minor secretory pathway for injectable radiopaque diagnostic agents. In patients with normal renal function, minimal amounts of contrast media are secreted unchanged. However, in uremic patients small amounts of free iodides resulting from deiodination prior to administration or in vivo , have been detected in the saliva.
Diatrizoate salts cross the placental barrier in humans by simple diffusion and appear to enter fetal tissue passively. No apparent harm to the fetus was observed when diatrizoate sodium and diatrizoate meglumine were injected intravenously 24 hours prior to delivery. However, abnormal neonatal opacification of the small intestine and colon were detected 4 to 6 days after delivery. Procedures including radiation involve a certain risk related to the exposure of the fetus. (See PRECAUTIONS—General, Pregnancy Category C.)
Injectable radiopaque diagnostic agents are excreted unchanged in human milk. (See PRECAUTIONS-General, Nursing Mothers.)
HYPAQUE meglumine 60 percent can be administered as an intravenous bolus for brain tissue enhancement using computerized tomography. Increased tissue contrast differential for the scan is achieved either because of increased vascular (arterial, venous, or capillary bed) contrast or by blood brain barrier penetration of the medium (or its absence) in certain localized areas of disrupted vascular permeability. The degree of tissue enhancement caused by increased blood contrast is directly related to blood iodine content. However, the degree of enhancement due to extravascular accumulation of iodine resulting from blood brain barrier disruption will depend on the extent of disruption, the blood level of iodine, and the time delay prior to scanning. The nature of the pathology will determine whether an immediate or delayed scan is optimal.
The anti-inflammatory and antiedema effects in patients receiving steroid therapy have interfered with the expected distribution of CT tissue enhancement on the scan in certain diseases.
Hypaque Sodium Indications and Usage
HYPAQUE meglumine 60 percent is indicated for excretory urography; cerebral angiography; peripheral arteriography; venography; operative, T-tube, or percutaneous transhepatic cholangiography; splenoportography; arthrography; discography; and contrast enhancement of computed tomographic head imaging.
Diatrizoate salts are used in small, medium, and large dose urography (see Dosage and Administration-EXCRETORY UROGRAPHY). Visualization of the urinary tract can be achieved by either direct intravenous bolus injection, intravenous drip infusion, or incidentally following intra-arterial procedures. Visualization of the urinary tract is delayed in infants less than 1 month old, and in patients with urinary tract obstruction (see CLINICAL PHARMACOLOGY).
Injectable radiopaque contrast media may be used to refine diagnostic precision in areas of the brain which may not otherwise have been satisfactorily visualized.
Radiopaque diagnostic agents may be useful to investigate the presence and extent of certain malignancies such as: gliomas including malignant gliomas, glioblastomas, astrocytomas, oligodendrogliomas and gangliomas, ependymomas, medulloblastomas, meningiomas, neuromas, pinealomas, pituitary adenomas, craniopharyngiomas, germinomas, and metastatic lesions.
The usefulness of contrast enhancement for the investigation of the retrobulbar space and in cases of low grade or infiltrative glioma has not been demonstrated.
In calcified lesions, there is less likelihood of enhancement. Following therapy, tumors may show decreased or no enhancement.
The opacification of the inferior vermis following contrast media administration has resulted in false-positive diagnosis in a number of normal studies.
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