Cinnarizine

Cinnarizine belongs to the diphenylmethylpiperazine class and works as both an antihistamine and a calcium channel blocker. It is used to treat nausea and vomiting stemming from motion sickness, chemotherapy, vertigo, or Ménière’s disease. It is also a major cause of drug-induced parkinsonism.

First synthesized in 1955 by Janssen Pharmaceutica under the code R1575, its nonproprietary name combines the cinnamyl group attached to the benzhydrylpiperazine core with the suffix “-rizine,” which is standard for antihistamines and cerebral or peripheral vasodilators. It is not sold in the United States or Canada. The British Royal Navy has cited it as one of the most commonly used drugs for seasickness.

For medical use, cinnarizine mainly addresses nausea and vomiting from motion sickness, vertigo, Ménière’s disease, or Cogan’s syndrome. It is one of the few drugs that helps with chronic vertigo and tinnitus in Ménière’s disease. In a clinical study of 181 patients, treatment reduced moderate vertigo episodes by 65.8% and severe vertigo by 89.8%.

The drug works by blocking signal transmission between the inner ear’s vestibular apparatus and the hypothalamus’s vomiting center. It does this by limiting activity in vestibular hair cells that detect movement. This reduces the mismatch between signals from inner ear motion receptors and visual input, so the brain is less confused about whether the body is moving or still. The vomiting that occurs in motion sickness may be a physiological compensation to keep the person still while the brain adjusts, though the evolutionary reason remains unknown.

For balance problems and vertigo, cinnarizine is usually taken two or three times daily, depending on the dose. For motion sickness, it is taken at least two hours before travel and then every four hours during the trip. A 2012 study comparing it to transdermal scopolamine for seasickness found scopolamine significantly more effective and with fewer side effects, making it likely a better choice for naval crews and sea travelers. However, because cinnarizine causes drowsiness, it is generally not suitable for pilots or aircrew who need to stay alert.

Cinnarizine can be used by scuba divers without raising the risk of central nervous system oxygen toxicity, which can cause seizures and is a concern in closed-circuit oxygen diving.