Cyclizine
Class: antiemetic – antihistaminic, antimuscarinic
Indications: nausea/vomiting (including motion sickness, vertigo). Nausea related to vestibular system irritation or raised intracranial pressure
Contraindications/cautions: prostatic hypertrophy, urinary retention, narrow angle glaucoma
Adverse reactions: common: drowsiness, headache, psychomotor impairment, restlessness, dry mouth, blurred vision, constipation; less common: insomnia, hallucinations (more common: in elderly), cardiac arrhythmias
Metabolism/clearance: extensively hepatically metabolised mainly to inactive metabolites that are predominantly renally excreted
Interactions:
- additive CNS effects with other CNS depressants e.g. benzodiazepines (e.g. lorazepam), phenothiazines (e.g. chlorpromazine), tricyclic antidepressants (e.g. amitriptyline), opioids, alcohol
| Dosing: | |
|---|---|
| oral: | 50 mg 2 to 3 times a day (cyclizine hydrochloride) & 50 mg prn – usual maximum dose 200 mg/24 hours |
| subcut: | bioavailability is 50% so subcut dose 75 to 150 mg/24 hours (cyclizine lactate) (well diluted) |
| rectal: | not available |
Syringe driver: see syringe driver compatibility table. Diluent WFI. Incompatible with NaCl
Mechanism of action: An H1 and muscarinic antagonist thought to act on the vestibular system & in the vomiting centre in the CNS and has anticholinergic properties
Onset of action: 30 to 60 minutes Duration of action: 4 to 6 hours
Peak concentration: approx 2 hours
Notes:
- although there is a theoretical interaction with prokinetic antiemetics (prokinetics stimulate the gut while cyclizine slows it down) use together is common and may be justified on the basis of central nervous system receptors antagonism
- can accumulate in repeated use – caution in elderly & in hepatic & renal impairment & reduce dosing frequency to twice daily