July 25, 2016
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Provocholine® (methacholine chloride) (methacholine i chloride powder for inhalation) is to be administered only by inhalation. When administered orally or by injection, overdosage with methacholine chloride can result in a syncopal reaction, with cardiac arrest and loss of consciousness. Serious toxic reactions should be treated with 0.5 mg to 1 mg of atropine sulfate, administered IM or IV.

The acute (24 hour) oral LD50 of methacholine chloride and related compounds is 1100 mg/kg in the mouse and 750 mg/kg in the rat.

Cynomolgus monkeys were exposed to a 2% (20 mg/mL) aerosol of methacholine chloride in acute (10 minute) and subchronic (7 day) inhalation toxicity studies. In the former study, animals exposed to the aerosol for up to 10 minutes demonstrated an increase in respiratory rate and decrease in tidal volume after 30 seconds. These changes peaked at 2 minutes and were followed by a rise in pulmonary resistance and a decrease in compliance. Pulmonary function returned to normal 20 to 25 minutes after exposure ended. In the 7 day study, monkeys were given daily inhalations equivalent to the maximum and roughly five times the maximum standard human dose. Although the typical pulmonary response/recovery sequence was observed, distinct changes in airway resistance were noted at the end of the study. These changes were not rapidly reversed in the maximum equivalent standard dose group, which was observed for 9 weeks.


Provocholine® (methacholine chloride powder for inhalation) is contraindicated in patients with known hypersensitivity to this drug or to other parasympathomimetic agents.

Repeated administration of Provocholine® (methacholine chloride) by inhalation other than on the day that a patient undergoes challenge with increasing doses is contraindicated.

Inhalation challenge should not be performed in patients receiving any beta-adrenergic blocking agent because in such patients responses to methacholine chloride can be exaggerated or prolonged, and may not respond as readily to accepted modalities of treatment (see WARNINGS box).

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 9/25/2008


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