Antihistamine overdosage reactions may vary from central nervous system depression to stimulation especially in pediatric patients. Also, atropine-like signs and symptoms (dry mouth; fixed, dilated pupils; flushing, etc.) as well as gastrointestinal symptoms may occur.

If vomiting has not occurred spontaneously the patient should be induced to vomit with syrup of ipecac. If the patient is unable to vomit, perform gastric lavage followed by activated charcoal. Isotonic or 1/2 isotonic saline is the lavage of choice. Precautions against aspiration must be taken especially in infants and children.

When life threatening CNS signs and symptoms are present, intravenous physostigmine salicylate may be considered. Dosage and frequency of administration are dependent on age, clinical response, and recurrence after response. (See package circulars for physostigmine products.)

Saline cathartics, as milk of magnesia, by osmosis draw water into the bowel and, therefore, are valuable for their action in rapid dilution of bowel content. Stimulants should not be used.

Vasopressors may be used to treat hypotension.

The oral LD₅₀ of cyproheptadine (cyproheptadine hydrochloride) is 123 mg/kg, and 295 mg/kg in the mouse and rat, respectively.

Newborn or Premature Infants

This drug should not be used in newborn or premature infants.

Nursing Mothers

Because of the higher risk of antihistamines for infants generally and for newborns and prematures in particular, antihistamine therapy is contraindicated in nursing mothers.

Other Conditions

Hypersensitivity to cyproheptadine (cyproheptadine hydrochloride) and other drugs of similar chemical structure:

Monoamine oxidase inhibitor therapy (see PRECAUTIONS: DRUG INTERACTIONS)
Angle-closure glaucoma
Stenosing peptic ulcer
Symptomatic prostatic hypertrophy
Bladder neck obstruction
Pyloroduodenal obstruction
Elderly, debilitated patients

Last reviewed on RxList: 4/3/2009
This monograph has been modified to include the generic and brand name in many instances.