Contraindications/Precautions
Cyclizine should not be given to those patients with a known hypersensitivity to cyclizine.
Cyclizine is extensively metabolized in the liver, and caution is recommended in dosing those with hepatic disease; some
manufacturers recommend avoidance of the drug in liver disease.[44423] Less than 1% of the drug is excreted unchanged in
the urine; however, metabolites are extensively excreted in the urine and some manufacturers recommend cautious dosing
in those with significant renal impairment, such as patients with renal failure.[44423]
The anticholinergic activity of H antagonists (antihistamines) like cyclizine may result in thickened bronchial secretions in
the respiratory tract thereby aggravating an acute asthmatic attack, or chronic obstructive pulmonary disease (COPD) such as
emphysema or bronchitis. Although H antagonists should generally be avoided during an acute asthmatic attack, the use of
antihistamines is not precluded in all asthmatic or COPD patients. Because histamine is known to be a bronchoconstricting
substance in asthma, it is logical that antihistamines could reverse some of the harmful effects of histamine in patients with an
allergic component to their asthma. Antihistamines are typically not contraindicated in asthma unless previous adverse
reactions to the drugs have been observed.
Cyclizine should be used conservatively in patients with closedangle
glaucoma. Increased intraocular pressure may occur
from the anticholinergic actions of the drug, precipitating an acute attack of glaucoma. Elderly patients are more susceptible
to the anticholinergic effects of H antagonists, including possible precipitation of undiagnosed glaucoma. Other ocular
effects resulting from the anticholinergic effects of cyclizine include dry eyes or blurred vision. This may be of significance in
the elderly and wearers of contact lenses.
Because of the anticholinergic effects inherent to H antagonists like cyclizine, a worsening of symptoms may be seen in
patients with bladder obstruction, GI obstruction or ileus, benign prostatic hypertrophy, or urinary retention. Geriatric patients
are more susceptible to the anticholinergic effects of drugs since there is a decline in endogenous cholinergic activity that
occurs with age.
Drowsiness may occur during cyclizine use. Patients receiving this drug should be advised to avoid driving or operating
machinery or performing other tasks that require mental alertness until they know how the drug affects them. Because
ethanol or other CNS depressants may have additive effects with antihistamines, ethanol intoxication should be avoided
while taking cyclizine.[43278]
Although cardiovascular effects of piperazine antihistamines like cyclizine are uncommon, H antagonists should generally