Pharmacology Of Diatrizoate

Indication	Used, alone or in combination, for a wide variety of diagnostic imaging methods, including angiography, urography, cholangiography, computed tomography, hysterosalpingography, and retrograde pyelography. It can be used for imaging the gastrointestinal tract in patients allergic to barium.
Pharmacodynamics	Diatrizoate is the most commonly used water-soluble, iodinated, radiopaque x-ray contrast medium. Radiopaque agents are drugs used to help diagnose certain medical problems. They contain iodine, which blocks x-rays. Depending on how the radiopaque agent is given, it localizes or builds up in certain areas of the body. The resulting high level of iodine allows the x-rays to make a "picture" of the area. The areas of the body in which the radiopaque agent localizes will appear white on the x-ray film. This creates the needed distinction, or contrast, between one organ and other tissues. The contrast will help the doctor see any special conditions that may exist in that organ or part of the body.
Mechanism of action	Diatrizoate is an iodine-containing X-ray contrast agent. Iodated contrast agents were among the first contrast agents developed. Iodine is known to be particular electron-dense and to effectively scatter or stop X-rays. A good contrast agent requires a high density of electron-dense atoms. Therefore, the more iodine, the more "dense" the x-ray effect. Iodine based contrast media are water soluble and harmless to the body. These contrast agents are sold as clear colorless water solutions, the concentration is usually expressed as mg I/ml. Modern iodinated contrast agents can be used almost anywhere in the body. Most often they are used intravenously, but for various purposes they can also be used intraarterially, intrathecally (the spine) and intraabdominally - just about any body cavity or potential space.
Absorption	Not Available
Volume of distribution	Not Available
Protein binding	Not Available
Metabolism	Not Available
Route of elimination	However, it is not metabolized but excreted unchanged in the urine, each diatrizoate molecule remaining "obligated" to its sodium moiety. The liver and small intestine provide the major alternate route of excretion for diatrizoate. Injectable radiopaque diagnostic agents are excreted unchanged in human milk. Saliva is a minor secretory pathway for injectable radiopaque diagnostic agents.
Half life	Not Available
Clearance	Not Available
Toxicity	High osmolal radiocontrast agents like diatrizoate are cytotoxic to renal cells. The toxic effects include apoptosis, cellular energy failure, disruption of calcium homeostasis, and disturbance of tubular cell polarity, and are thought to be linked to oxidative stress.

Pharmacology Of Gadodiamide

Indication	For intravenous use in MRI to visualize lesions with abnormal vascularity (or those thought to cause abnormalities in the blood-brain barrier) in the brain (intracranial lesions), spine, and associated tissues.
Pharmacodynamics	Not Available
Mechanism of action	Based on the behavior of protons when placed in a strong magnetic field, which is interpreted and transformed into images by magnetic resonance (MR) instruments. Paramagnetic agents have unpaired electrons that generate a magnetic field about 700 times larger than the proton's field, thus disturbing the proton's local magnetic field. When the local magnetic field around a proton is disturbed, its relaxation process is altered. MR images are based on proton density and proton relaxation dynamics. MR instruments can record 2 different relaxation processes, the T1 (spin-lattice or longitudinal relaxation time) and the T2 (spin-spin or transverse relaxation time). In magnetic resonance imaging (MRI), visualization of normal and pathological brain tissue depends in part on variations in the radiofrequency signal intensity that occur with changes in proton density, alteration of the T1, and variation in the T2. When placed in a magnetic field, gadodiamide shortens both the T1 and the T2 relaxation times in tissues where it accumulates. At clinical doses, gadodiamide primarily affects the T1 relaxation time, thus producing an increase in signal intensity. Gadodiamide does not cross the intact blood-brain barrier; therefore, it does not accumulate in normal brain tissue or in central nervous system (CNS) lesions that have not caused an abnormal blood-brain barrier (e.g., cysts, mature post-operative scars). Abnormal vascularity or disruption of the blood-brain barrier allows accumulation of gadodiamide in lesions such as neoplasms, abscesses, and subacute infarcts.
Absorption	Not Available
Volume of distribution	200 ± 61 mL/kg
Protein binding	Not Available
Metabolism	There is no detectable biotransformation or decomposition of gadodiamide.
Route of elimination	Gadodiamide is eliminated primarily in the urine.
Half life	Two-compartment model with mean distribution and elimination half-lives (reported as mean ± SD) of 3.7 ± 2.7 minutes and 77.8 ± 16 minutes, respectively.
Clearance	Renal cl=1.7 mL/min/kg Plasma cl=1.8 mL/min/kg
Toxicity	Not Available

Pharmacology Of Metyrapone

Indication	Used as a diagnostic drug for testing hypothalamic-pituitary ACTH function. Occasionally used in Cushing's syndrome.
Pharmacodynamics	Metopirone is an inhibitor of endogenous adrenal corticosteroid synthesis.
Mechanism of action	The pharmacological effect of Metopirone is to reduce cortisol and corticosterone production by inhibiting the 11-ß-hydroxylation reaction in the adrenal cortex. Removal of the strong inhibitory feedback mechanism exerted by cortisol results in an increase in adrenocorticotropic hormone (ACTH) production by the pituitary. With continued blockade of the enzymatic steps leading to production of cortisol and corticosterone, there is a marked increase in adrenocortical secretion of their immediate precursors, 11-desoxycortisol and desoxycorticosterone, which are weak suppressors of ACTH release, and a corresponding elevation of these steroids in the plasma and of their metabolites in the urine. These metabolites are readily determined by measuring urinary 17-hydroxycorticosteroids (17-OHCS) or 17-ketogenic steroids (17-KGS). Because of these actions, metopirone is used as a diagnostic test, with urinary 17-OHCS measured as an index of pituitary ACTH responsiveness. Metopirone may also suppress biosynthesis of aldosterone, resulting in a mild natriuresis.
Absorption	Absorbed rapidly and well when administered orally. Peak plasma concentrations are usually reached 1 hour after administration.
Volume of distribution	Not Available
Protein binding	Not Available
Metabolism	Hepatic. The major biotransformation is reduction of the ketone to metyrapol, an active alcohol metabolite. Metyrapone and metyrapol are both conjugated with glucuronide.
Route of elimination	After administration of 4.5 g metyrapone (750 mg every 4 hours), an average of 5.3% of the dose was excreted in the urine in the form of metyrapone (9.2% free and 90.8% as glucuronide) and 38.5% in the form of metyrapol (8.1% free and 91.9% as glucuronide) within 72 hours after the first dose was given.
Half life	1.9 ±0.7 hours.
Clearance	Not Available
Toxicity	Oral LD50 in rats is 521 mg/kg. One case has been recorded in which a 6-year-old girl died after two doses of Metopirone, 2 g. Symptoms of overdose include cardiac arrhythmias, hypotension, dehydration, anxiety, confusion, weakness, impairment of consciousness, nausea, vomiting, epigastric pain, and diarrhea.

Pharmacology Of Histamine Phosphate

Indication	Histamine phosphate is indicated as a diagnostic aid for evaluation of gastric acid secretory function.
Pharmacodynamics	Histamine stimulates gastric gland secretion, causing an increased secretion of gastric juice of high acidity. This action is probably due mainly to a direct action on parietal and chief gland cells.
Mechanism of action	Histamine acts directly on the blood vessels to dilate arteries and capillaries; this action is mediated by both H 1- and H 2-receptors. Capillary dilatation may produce flushing of the face, a decrease in systemic blood pressure, and gastric gland secretion, causing an increased secretion of gastric juice of high acidity. Increased capillary permeability accompanies capillary dilatation, producing an outward passage of plasma protein and fluid into the extracellular spaces, an increase in lymph flow and protein content, and the formation of edema. In addition, histamine has a direct stimulant action on smooth muscle, producing contraction if H 1-receptors are activated, or mostly relaxation if H 2-receptors are activated. Also in humans, the stimulant effect of histamine may cause contraction of the intestinal muscle. However, little effect is noticed on the uterus, bladder, or gallbladder. Histamine has some stimulant effect on duodenal, salivary, pancreatic, bronchial, and lacrimal glands. Histamine also can bind to H3 and H4 receptors which are involved in the CNS/PNS neurotransmitter release and immune system chemotaxis, respectively.
Absorption	Readily absorbed after parenteral administration
Volume of distribution	Not Available
Protein binding	Not Available
Metabolism	Primarily hepatic. Histamine is rapidly metabolized by methylation and oxidation. Methylation involves ring methylation and catalyzation by the enzyme histamine-N-methyltransferase, producing N-methylhistamine, which is mostly converted to N-methyl imidazole acetic acid. 2 to 3% excreted as free histamine, 4 to 8% as N-methylhistamine, 42 to 47% as N-methyl imidazole acetic acid, 9 to 11% as imidazole acetic acid, and 16 to 23% as imidazole acetic acid riboside
Route of elimination	Not Available
Half life	Not Available
Clearance	Not Available
Toxicity	LD50=807 mg/kg (mouse, oral). Side effects can lead to hypertension, hypotension, headache, dizziness, nervousness and tachycardia. Large overdoses can lead to seizures

Pharmacology Of Inulin

Indication	Historically used in an important medical test of renal function, specifically a measure of glomerular filtration rate. Sometimes used to help relieve symptoms of diabetes mellitus - a condition characterised by hyperglycemia and/or hyperinsulinemia.
Pharmacodynamics	The inulin test is a procedure by which the filtering capacity of the glomeruli (the main filtering structures of the kidney) is determined by measuring the rate at which inulin, the test substance, is cleared from blood plasma. Inulin is one of the more suitable and accurate substance to measure because it is a small, inert polysaccharide molecule that readily passes through the glomeruli. The inulin clearance test is performed by injecting inulin, waiting for it to be distributed, and then measuring plasma and urine inulin concentrations by various assays. As nutraceutical agents inulins may have antitumor, antimicrobial, hypolipidemic and hypoglycemic actions. They may also help to improve mineral absorption and balance and may have antiosteoporotic activity.
Mechanism of action	As a diagnostic agent, inulin is readily soluble and essentially indigestible. It readily passes through the blood and into the urine. It is neither secreted nor resorbed by the kidney making it an excellent indicator for renal clearance rates. The inulin clearance test has largely been succeeded by the creatinine clearance test as a measure of glomerular filtration rate. As a hypoglycemic agent, inulin is not digestible by human enzymes ptyalin and amylase, which are designed to digest starch. As a result, inulin passes through much of the digestive system intact. It is only in the colon that bacteria metabolise inulin, with the release of significant quantities of carbon dioxide and/or methane. Because inulin is not broken down into simple sugars (monosaccharides) by normal digestion, it does not elevate blood sugar levels, hence, helping diabetics regulate blood sugar levels.
Absorption	Poorly absorbed, passes through to urine unmetabolized
Volume of distribution	Not Available
Protein binding	None
Metabolism	Metabolized into carbon dioxide and methane by colonic bacteria
Route of elimination	Not Available
Half life	2-4 hours
Clearance	Not Available
Toxicity	Not Available

Pharmacology Of Bentiromide

Indication	Used as a screening test for exocrine pancreatic insufficiency and to monitor the adequacy of supplemental pancreatic therapy.
Pharmacodynamics	Bentiromide is a peptide used as a screening test for exocrine pancreatic insufficiency and to monitor the adequacy of supplemental pancreatic therapy. It is given by mouth as a noninvasive test. The amount of p-aminobenzoic acid and its metabolites excreted in the urine is taken as a measure of the chymotrypsin-secreting activity of the pancreas. Headache and gastrointestinal disturbances have been reported in patients taking bentiromide. Bentiromide is not available in the U.S. or Canada.
Mechanism of action	Bentiromide is a peptide that is broken down in the pancreas by chymotrypsin. By determining the output of unchanged bentiromide in the urine following oral administration, it is possible to determine the sufficiency of pancreatic activity.
Absorption	Not Available
Volume of distribution	Not Available
Protein binding	Not Available
Metabolism	Primarily hepatic. Enzymatic activity capable of hydrolyzing bentiromide has also been found in normal small intestine.
Route of elimination	Not Available
Half life	Not Available
Clearance	Not Available
Toxicity	Symptoms of overdose include shortness of breath and troubled breathing.

Pharmacology Of Ceruletide

Indication	Caerulein stimulates gastric, biliary, and pancreatic secretion; and certain smooth muscle. As such, it is used in paralytic ileus and as diagnostic aid in pancreatic malfunction.
Pharmacodynamics	Caerulein is a specific decapeptide similar in action and composition to the natural gastrointestinal peptide hormone cholecystokinin. It stimulates gastric, biliary, and pancreatic secretion; and certain smooth muscle.
Mechanism of action	Caerulein acts according to its similarity to the natural gastrointestinal peptide hormone cholecystokinin. Cholecystokinin is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein. Cholecystokinin is secreted by the duodenum, the first segment of the small intestine. There it binds to CCK receptors, activating them and causing downstream effects. Specifically, it results in the release of digestive enzymes and bile from the pancreas and gall bladder, respectively. It also acts as a hunger suppresant. Cholecystokinin is secreted by the duodenum when fat- or protein-rich chyme leaves the stomach and enters the duodenum. The hormone acts on the pancreas to stimulate the secretion of the enzymes lipase, amylase, trypsin, and chymotrypsin. Together these pancreatic enzymes catalyze the digestion of fat and protein. Cholecystokinin also stimulates both the contraction of the gall bladder, and the relaxtion of the Sphincter of Oddi (Glisson's Sphinctor), which delivers, (not secretes) bile into the small intestine. Bile salts serve to emulsify fats, thereby increasing the effectiveness with which enzymes can digest them.
Absorption	Absorbed following intravenous administration.
Volume of distribution	Not Available
Protein binding	Not Available
Metabolism	Not Available
Route of elimination	Not Available
Half life	Not Available
Clearance	Not Available
Toxicity	Not Available