Methacholine (trade name Provocholine) is a synthetic choline ester that acts as a muscarinic receptor agonist. Methacholine is primarily used to diagnose bronchial hyperreactivity, which is the hallmark of asthma and also occurs in chronic obstructive pulmonary disease. This is accomplished through the bronchial challenge test, or methacholine challenge, in which a subject inhales aerosolized methacholine, leading to bronchoconstriction.

Iohexol is a nonionic, water-soluble radiographic contrast medium. Organic iodine compounds block x-rays as they pass through the body, thereby allowing body structures containing iodine to be delineated in contrast to those structures that do not contain iodine. It is used in myelography, arthrography, nephroangiography, arteriography, and other radiographic procedures. Drugs which lower seizure threshold, especially phenothiazine derivatives including those used for their antihistaminic or antinauseant properties, are not recommended for use with Iohexol. Others include monoamine oxidase (MAO) inhibitors, tricyclic antidepressants, CNS stimulants, psychoactive drugs described as analeptics, major tranquilizers, or antipsychotic drugs. The most frequently reported adverse reactions are headache, mild to moderate pain including backache, neckache and stiffness, nausea, and vomiting.

Iopamidol is a nonionic, low-osmolar iodinated contrast agent. Iopamidol is indicated for angiography, pediatric angiocardiography, selective visceral arteriography and aortography, peripheral venography, and adult and pediatric intravenous excretory urography and intravenous adult and pediatric contrast enhancement of computed tomographic. Renal toxicity has been reported in a few patients with liver dysfunction who were given oral cholecystographic agents followed by intravascular contrast agents. Intravascular injection of contrast media is frequently associated with the sensation of warmth and pain especially in peripheral arteriography and venography. In angiocardiography the adverse reactions are: hot flashes, angina pectoris, flushing, bradycardia, hypotension, hives.

Malathion is an organophosphate insecticide, an inhibitor of cholinesterase. In low doses (0.5%) malathion is used for treatment of pediculosis and scabies.

Sincalide is a synthetically-prepared C-terminal octapeptide of naturally occurring hormone cholecystokinin. Sincalide causes gallbladder contraction and stimulates secretion of pancreatic enzymes, and this property of the drug is used in diagnostic purposes. It is discussed that the drug acts by binding and stimulating the CCK-A receptor which is expressed in the target tissues. FDA approved sincalide under the name KINEVAC.

Iothalamic Acid is an iodine-containing organic anion used as a radiocontrast agent. It is available as sodium iothalamate (Iothalamate sodium) and meglumine iothalamate (Iothalmate meglumine). It can be administered intravenously or intravesically (into the urinary bladder). Iothalamate is indicated to visualize specific regions of the vascular system and blood flow in these areas to help in the diagnosis and evaluation of neoplasms (known or suspected) or vascular diseases (congenital or acquired) that may cause changes in normal vascular anatomy or physiology. Iothalamate meglumine injection is indicated for use in cerebral angiography, peripheral arteriography or venography, arterial digital subtraction angiography1 , and intravenous digital subtraction angiography. Iothalamate meglumine and iothalamate sodium injection is indicated for use in selective coronary arteriography, selective renal arteriography, and in intravenous digital subtraction angiography. othalamate meglumine and iothalamate sodium injection and iothalamate sodium injection are indicated to visualize the aorta and its major branches. However, the injection of iothalamate meglumine and iothalamate sodium is preferred because it generally causes less severe hemodynamic, neurotoxic, and cardiotoxic effects than the individual injection of iothalamate sodium. Radioactive formulation is also available as sodium iothalamate I-125 Injection (GLOFIL-125). It is indicated for evaluation of glomerular filtration in the diagnosis or monitoring of patients with renal disease.

Tropicamide (Mydriacyl) is an anticholinergic used as a mydriatic.Tropicamide belongs to the group of medicines called anti-muscarinics. Tropicamide blocks the receptors in the muscles of the eye (muscarinic receptors). These receptors are involved controlling the pupil size and the shape of the lens. By blocking these receptors, tropicamide produces dilatation of the pupil (mydriasis) and prevents the eye from accommodating for near vision (cycloplegia). Tropicamide is given as eye drops to dilate the pupil and relax the lens so that eye examinations can be carried out thoroughly.

Fluorescein is a synthetic organic compound available as a dark orange/red powder slightly soluble in water and alcohol. It is widely used as a fluorescent tracer for many applications. Fluorescein was first synthesized by Adolf von Baeyer in 1871. It can be prepared from phthalic anhydride and resorcinol in the presence of zinc chloride via the Friedel-Crafts reaction. Fuorescein sodium is used intravenously in diagnostic fluorescein angiography or angioscopy of the retina and iris vasculature. Fluorescein sodium responds to electromagnetic radiation and light between the wavelengths of 465-490 nm and fluoresces, i.e., emits light at wavelengths of 520-530 nm. Thus, the hydrocarbon is excited by blue light and emits light that appears yellowish-green. Following intravenous injection of fluorescein sodium in an aqueous solution, the unbound fraction of the fluorescein can be excited with a blue light flash from a fundus camera as it circulates through the ocular vasculature, and the yellowish green fluorescence of the dye is captured by the camera. In the fundus, the fluorescence of the dye demarcates the retinal and/or choroidal vasculature under observation, distinguishing it from adjacent areas/structures. Topical, oral, and intravenous use of fluorescein can cause adverse reactions, including nausea, vomiting, hives, acute hypotension, anaphylaxis and related anaphylactoid reaction, causing cardiac arrest and sudden death due to anaphylactic shock. The most common adverse reaction is nausea, due to a difference in the pH from the body and the pH of the sodium fluorescein dye; a number of other factors however, are considered contributors as well. The nausea usually is transient and subsides quickly. Intravenous use has the most reported adverse reactions, including sudden death, but this may reflect greater use rather than greater risk. Both oral and topical uses have been reported to cause anaphylaxis, including one case of anaphylaxis with cardiac arrest (resuscitated) following topical use in an eye drop. Reported rates of adverse reactions vary from 1% to 6%. The higher rates may reflect study populations that include a higher percentage of persons with prior adverse reactions. The risk of an adverse reaction is 25 times higher if the person has had a prior adverse reaction. The risk can be reduced with prior (prophylactic) use of antihistamines and prompt emergency management of any ensuing anaphylaxis. A simple prick test may help to identify persons at greatest risk of adverse reaction

This compound belongs to the class of organic compounds known as aminobenzoic acids. These are benzoic acids containing an amine group attached to the benzene moiety. A commonly used x-ray contrast medium. 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. 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.

Barium sulfate, an insoluble in water substance, which was approved under the brand name E-Z-HD for use in double-contrast radiographic examinations of the esophagus, stomach and duodenum to visualize the gastrointestinal (GI) tract in patients 12 years and older. Due to its high atomic number, barium is opaque to x-rays and therefore acts as a positive contrast agent for radiographic studies.