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Chloral betaine
Chloral betaine (cloral betaine, Welldorm, Beta-Chlor) is a 1:1 chloral hydrate-betaine complex prodrug tablet hypnotic for short-term severe insomnia, 707 mg equal to 414 mg chloral hydrate, UK paediatric use restricted since 2021.
Chlorambucil
Chlorambucil, sold as Leukeran, is an oral nitrogen mustard alkylating agent approved in the United States in 1957, used mainly to treat chronic lymphocytic leukemia and malignant lymphomas.
Chlorambucil and obinutuzumab regimen
The chlorambucil and obinutuzumab regimen is a chemoimmunotherapy combination pairing oral chlorambucil with the anti-CD20 antibody obinutuzumab, approved in 2013 for previously untreated chronic lymphocytic leukemia.
Chloramphenicol
Chloramphenicol (Chloromycetin) is a broad-spectrum bacteriostatic antibiotic from Streptomyces venezuelae, discovered 1947, that binds the 50S ribosome peptidyl transferase center; now rarely used because of aplastic anemia risk and IARC Group 2A classification.
Chlordiazepoxide
Chlordiazepoxide (Librium) is the first marketed benzodiazepine, synthesized by Leo Sternbach at Hoffmann-La Roche, FDA approved February 24, 1960; a long-acting Schedule IV anxiolytic with a 24–48 hour half-life, used for anxiety and alcohol withdrawal.
Chlorhexidine
Chlorhexidine (Hibitane) is a cationic bisbiguanide antiseptic developed by ICI in the UK in the early 1950s, used for surgical skin preparation, catheter care, mouthwash, and umbilical cord antisepsis; most effective combined with alcohol.
Chlorine gas poisoning
Chlorine gas poisoning: lung injury from inhaling Cl2, a heavier-than-air, water-soluble irritant gas that forms hydrochloric and hypochlorous acid in tissue. No antidote; supportive care. Civilian mortality about 0.6%; first used as a weapon at Ypres, 1915.
Chlormerodrin
Chlormerodrin (Neohydrin, Mercloran) is an organomercury urea-derivative diuretic, withdrawn from use, whose 197Hg/203Hg-labeled forms were the first radiopharmaceuticals for renal imaging.
Chlormezanone
Chlormezanone (Trancopal, CAS 80-77-3), a non-benzodiazepine anxiolytic and central muscle relaxant marketed from 1960, was discontinued worldwide in 1996 after links to toxic epidermal necrolysis and Stevens-Johnson syndrome.
Chloroprocaine
Chloroprocaine (2-chloroprocaine) is a short-acting ester local anesthetic of the PABA group, hydrolyzed by pseudocholinesterase within seconds, used for infiltration, nerve block, and epidural anesthesia but not spinal injection.
Chlorotrianisene
Chlorotrianisene (Tace, CAS 569-57-3) is a synthetic non-steroidal triphenylethylene estrogen and prodrug, once used for menopausal symptoms, prostate cancer palliation, and lactation suppression; now discontinued and Prop 65 listed.
Chlorphenamine
Chlorphenamine (chlorpheniramine), brand Piriton, Chlor-Trimeton: a first-generation sedating H1 antihistamine alkylamine used for hay fever, hives, and allergy symptoms; FDA approved 1950.
Chlorphenesin carbamate
Chlorphenesin carbamate (Maolate, Rinlaxer; CAS 886-74-8) is the carbamate ester of chlorphenesin, a centrally acting skeletal muscle relaxant for painful muscle spasm, FDA-approved in 1965 and still used in veterinary medicine.
Chlorphenoxamine
Chlorphenoxamine (Phenoxene, Systral) is a first-generation H1-antihistamine and anticholinergic, a diphenhydramine congener used as an antipruritic and formerly for parkinsonism; CAS 77-38-3, ATC D04AA34.
Chlorphentermine
Chlorphentermine (Pre-Sate, Desopimon, Avipron) is a chlorinated amphetamine-derived sympathomimetic formerly prescribed as an anorectic for obesity; withdrawn after causing phospholipidosis and pulmonary hypertension, it remains a DEA Schedule III substance.
Chlorproguanil
Chlorproguanil (Lapdap, with dapsone) is a biguanide antifolate antimalarial, a proguanil analog with an extra chlorine atom, developed at Liverpool as a cheap SP replacement and withdrawn in 2008 for G6PD-deficient hemolysis.
Chlorpromazine
Chlorpromazine is a phenothiazine antipsychotic, the first effective medication for schizophrenia, synthesized at Rhône-Poulenc and introduced into psychiatry in Paris in 1952; it remains available as an inexpensive generic.
Chlorpropamide
Chlorpropamide, formerly marketed as Diabinese, is a first-generation sulfonylurea introduced in 1960 for type 2 diabetes, distinguished by a roughly 36-hour half-life and also used for its antidiuretic effect in diabetes insipidus.
Chlorprothixene
Chlorprothixene (Taractan, Truxal) is a low-potency first-generation thioxanthene antipsychotic first marketed in 1959 by Lundbeck, a sedative D2 antagonist with 5-HT2C, H1 and M3 affinity, still used in Europe.
Chlortalidone
Chlortalidone (chlorthalidone) is a long-acting thiazide-like diuretic for hypertension, U.S.-approved since 1960, half-life 40-60 hours, the ALLHAT comparator drug, with hypokalemia and metabolic side effects.
Chlorzoxazone
Chlorzoxazone, formerly sold as Parafon Forte and Remular, is a centrally acting skeletal muscle relaxant approved in the United States in 1958 for acute, painful musculoskeletal conditions.
Choanal atresia
Choanal atresia: congenital bony or membranous obstruction of the posterior nasal openings (choanae), incidence 1:5000–8000, female-predominant, linked to CHARGE syndrome; bilateral form is a neonatal airway emergency treated by endoscopic transnasal repair, with stenting increasingly questioned.
CHOCO-PAD study
CHOCO-PAD (NCT06933992) is a prospective, multicenter, single-arm observational trial at eight Chinese centres testing the Chocolate PTA balloon catheter, a nitinol-constrained angioplasty balloon, in 171 PAD patients, with 12-month target lesion patency as the primary outcome.
Choking
Choking is airway obstruction by a foreign body. Covers partial versus complete obstruction, 2025 AHA and Red Cross first-aid sequences, hypoxia timelines, mortality statistics, complications, and the anti-choking device evidence.
Cholangiocarcinoma
Cholangiocarcinoma (bile duct cancer; iCCA, pCCA/Klatskin, dCCA): adenocarcinoma of biliary epithelium, second most common primary liver cancer. Risk: PSC, liver flukes, cirrhosis; drivers FGFR2 fusions, IDH1/2, KRAS; treated by resection, transplant protocols, chemoimmunotherapy.
Cholangiography
Cholangiography is the radiologic or endoscopic imaging of the bile ducts with contrast agents or MRI, performed to diagnose duct obstruction, stones, strictures, and leaks.
Cholangiopancreatography
Cholangiopancreatography visualizes the bile and pancreatic ducts to diagnose ductal disease, in two forms: noninvasive MRI (MRCP) and endoscopic retrograde contrast imaging (ERCP), which is mainly therapeutic.
Cholangioscopy
Cholangioscopy is an endoscopic technique in which a very thin endoscope is advanced into the bile ducts, most often during ERCP, to fragment difficult stones and biopsy indeterminate strictures.
Cholangitis
Cholangitis: inflammation of the bile ducts, intrahepatic or extrahepatic. Covers acute ascending cholangitis (obstruction plus infection, treated with antibiotics and ERCP drainage) and chronic sclerosing forms including PSC and IgG4-related disease.
Cholecalciferol
Cholecalciferol (vitamin D3), the animal form of vitamin D, is made in skin from 7-dehydrocholesterol by UVB, activated by liver and kidney hydroxylations, and raises serum 25(OH)D more effectively than ergocalciferol (D2).