Cyclizine
Encyclopedia
Cyclizine is an antihistamine
Antihistamine
An H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...

 drug used to treat nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...

 and dizziness
Dizziness
Dizziness refers to an impairment in spatial perception and stability. The term is somewhat imprecise. It can be used to mean vertigo, presyncope, disequilibrium, or a non-specific feeling such as giddiness or foolishness....

 associated with motion sickness
Motion sickness
Motion sickness or kinetosis, also known as travel sickness, is a condition in which a disagreement exists between visually perceived movement and the vestibular system's sense of movement...

, vertigo
Vertigo (medical)
Vertigo is a type of dizziness, where there is a feeling of motion when one is stationary. The symptoms are due to a dysfunction of the vestibular system in the inner ear...

 and post-operatively following administration of general anaesthesia
General anaesthesia
General anaesthesia is a state of unconsciousness and loss of protective reflexes resulting from the administration of one or more general anaesthetic agents...

 and opioid
Opioid
An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract...

s.

Indications

Nausea
Nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

, vomiting
Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...

 and dizziness
Dizziness
Dizziness refers to an impairment in spatial perception and stability. The term is somewhat imprecise. It can be used to mean vertigo, presyncope, disequilibrium, or a non-specific feeling such as giddiness or foolishness....

 associated with motion sickness
Motion sickness
Motion sickness or kinetosis, also known as travel sickness, is a condition in which a disagreement exists between visually perceived movement and the vestibular system's sense of movement...

, vertigo
Vertigo (medical)
Vertigo is a type of dizziness, where there is a feeling of motion when one is stationary. The symptoms are due to a dysfunction of the vestibular system in the inner ear...

 and post-operatively following administration of general anaesthesia
General anaesthesia
General anaesthesia is a state of unconsciousness and loss of protective reflexes resulting from the administration of one or more general anaesthetic agents...

 and opioid
Opioid
An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract...

s.
It is sometimes given in hyperemesis gravidarum (morning sickness) although the manufacturer advises avoid in pregnancy. Off licence use often occurs with specialists in hospitals to treat inpatients who have become severely dehydrated in pregnancy.
An off-label use is as an opioid/opiate potentiator.

The drug Diconal is a combination of cyclizine with the opioid dipipanone
Dipipanone
Dipipanone is a strong opioid analgesic drug, used for very severe pain in cases where other analgesics are unsuitable, for instance where morphine is indicated but cannot be used due to the patient being allergic to morphine.-Dosage forms:...

.
Dipipanone is a schedule I controlled substance in the US, due to its high abuse potential.

Contraindications

Its antimuscarinic action warrants caution in patients with prostatic hypertrophy
Benign prostatic hyperplasia
Benign prostatic hyperplasia also known as benign prostatic hypertrophy , benign enlargement of the prostate , and adenofibromyomatous hyperplasia, refers to the increase in size of the prostate....

, urinary retention, or glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...

. Liver disease exacerbates its sedative effects.

Adverse effects

Common (over 10%) – Drowsiness, xerostomia
Xerostomia
Xerostomia is the medical term for the subjective complaint of dry mouth due to a lack of saliva. Xerostomia is sometimes colloquially called pasties, cottonmouth, drooth, or doughmouth. Several diseases, treatments, and medications can cause xerostomia. It can also be exacerbated by smoking or...

 (dry mouth)

Uncommon (1% to 10%) – Headache, psychomotor impairment, and antimuscarinic effects such as urinary retention
Urinary retention
Urinary retention, also known as ischuria, is a lack of ability to urinate. It is a common complication of benign prostatic hyperplasia , although it can also be caused by nerve dysfunction, constipation, infection, or medications...

, diplopia (blurred vision), dermatitis, and gastro-intestinal disturbances.

Rare – Hypersensitivity reactions (bronchospasm, angioedema, anaphylaxis, rashes and photosensitivity reactions), extrapyramidal
Extrapyramidal
Extrapyramidal can refer to:* Extrapyramidal system* Extrapyramidal symptoms...

 effects, dizziness, confusion, depression, sleep disturbances, tremor, liver dysfunction and hallucinations

Formulations

As cyclizine hydrochloride 50 mg tablets and cyclizine lactate solution for intramuscular or intravenous injection (brand names: Valoid in UK and Marezine, Marzine and Emoquil in US). Cyclizine HCl 25 mg is marketed as Bonine for Kids in the US.

Pharmacology

Cyclizine is a piperazine
Piperazine
Piperazine is an organic compound that consists of a six-membered ring containing two opposing nitrogen atoms. Piperazine exists as small alkaline deliquescent crystals with a saline taste....

 derivative with histamine H1-receptor antagonist (antihistamine
Antihistamine
An H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...

) activity. The precise mechanism of action in inhibiting the symptoms of motion sickness is not well understood. It may have effects directly on the labyrinthine apparatus and on the chemoreceptor trigger zone
Chemoreceptor trigger zone
The chemoreceptor trigger zone , is an area of the medulla that receives inputs from blood-borne drugs or hormones, and communicates with the vomiting center, to initiate vomiting. The CTZ is close to the area postrema on the floor of the fourth ventricle and is outside of the blood-brain barrier...

. Cyclizine exerts a central anticholinergic
Anticholinergic
An anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. An example of an anticholinergic is dicycloverine, and the classic example is atropine....

 (antimuscarinic) action.

History

Cyclizine was developed in the American division of pharmacy company Burroughs Wellcome (today GlaxoSmithKline
GlaxoSmithKline
GlaxoSmithKline plc is a global pharmaceutical, biologics, vaccines and consumer healthcare company headquartered in London, United Kingdom...

) during a research involving many drugs of the antihistamine group. Cyclizine was quickly clinically found as a potent and long-acting antiemetic. Company named the substance – or more precisely cyclizine's hydrochloride
Hydrochloride
In chemistry, hydrochlorides are salts resulting, or regarded as resulting, from the reaction of hydrochloric acid with an organic base . This is also known as muriate, derived from hydrochloric acid's other name: muriatic acid....

 form which it usually appears in – "marezine hydrochloride" and started to sell it in the United States under trade name Marezine. Selling was begun in France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 under trade name Marzine in 1965.

The substance received more credit when NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 chose it as a space antiemetic for the first occupied moon flight
Apollo 11
In early 1969, Bill Anders accepted a job with the National Space Council effective in August 1969 and announced his retirement as an astronaut. At that point Ken Mattingly was moved from the support crew into parallel training with Anders as backup Command Module Pilot in case Apollo 11 was...

. Cyclizine was introduced to many countries as a common antiemetic. It is an over-the-counter drug in many countries because it has been well tolerated, although it has not been very much studied.

Recreational use

Some people using methadone recreationally combine cyclizine with their methadone dose, a combination that is known to produce strong psychoactive effects.
It has also been used recreationally by teenagers for its anticholinergic
Anticholinergic
An anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. An example of an anticholinergic is dicycloverine, and the classic example is atropine....

effects to induce hallucinations.
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