Dicycloverine, also known as dicyclomine, sold under the brand name Bentyl in the US, is a medication that is used to treat spasms of the intestines such as occur in irritable bowel syndrome. It is taken by mouth or by injection into a muscle. While it has been used in baby colic and enterocolitis, evidence does not support these uses. Common side effects include dry mouth, blurry vision, weakness, sleepiness, and lightheadedness. Serious side effects may include psychosis and breathing problems in babies. Use in pregnancy appears to be safe while use during breastfeeding is not recommended. How it works is not entirely clear. Dicycloverine was approved for medical use in the United States in 1950. It is available as a generic medication. In 2020, it was the 147th most commonly prescribed medication in the United States, with more than 4million prescriptions. Medical uses Dicyclomine is used to treat the symptoms of irritable bowel syndrome, specifically hypermotility, in adults. As of 2016, clinical guidelines recommended dicycloverine and other antispasmodics for IBS with diarrhea as a first line treatment. Contraindications This medicine should not be used for people who have an obstructive GI or urinary condition, severe ulcerative colitis, reflux, any unstable cardiac condition, glaucoma, myasthenia gravis, and anyone who is acutely bleeding. It should not be given to children or infants with colic due to the risks of convulsions, difficult breathing, irritability, and restlessness, and there is little evidence to support the efficacy in such use in any case. Because dicycloverine is known to impair thinking and coordination, people taking the drug should avoid driving or operating machinery. The effect on the baby during pregnancy or breastfeeding is not well understood. Adverse effects Dicycloverine can cause a range of anticholinergic side effects such as dry mouth, nausea, blurred vision, dizziness, confusion, severe constipation, stomach pain, heart palpitations, difficulty urinating, and seizures. Pharmacology Dicycloverine blocks the action of acetylcholine on cholinergic receptors on smooth muscles in the GI tract, relaxing the smooth muscle. History Dicycloverine was first synthesized chemically in the United States circa 1945 by scientists at William S. Merrell Company. It was first marketed in 1952 for gastrointestinal disorders, including colic in infants. The INN name "dicycloverine" was recommended in 1959. It was included in the combination drug for morning sickness called Bendectin, along with doxylamine and vitamin B6 which was launched in the US 1956; dicyclomine was removed