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The following rates of adverse reactions to pirbuterol are based on single- and multiple-dose clinical trials involving 761 patients, 400 of whom received multiple doses (mean duration of treatment was 2.5 months and maximum was 19 months).

The following were the adverse reactions reported more frequently than 1 in 100 patients:

CNS: nervousness (6.9%), tremor (6.0%), headache (2.0%), dizziness (1.2%).

Cardiovascular: palpitations (1.7%), tachycardia (1.2%).

Respiratory: cough (1.2%).

Gastrointestinal: nausea (1.7%).

The following adverse reactions occurred less frequently than 1 in 100 patients and there may be a causal relationship with pirbuterol:

CNS: depression, anxiety, confusion, insomnia, weakness, hyperkinesia, syncope.

Cardiovascular: hypotension, skipped beats, chest pain.

Gastrointestinal: dry mouth, glossitis, abdominal pain/cramps, anorexia, diarrhea, stomatitis, nausea and vomiting.

Ear, Nose and Throat: smell/taste changes, sore throat.

Dermatological: rash, pruritus.

Other:numbness in extremities, alopecia, bruising, fatigue, edema, weight gain, flushing.

Other adverse reactions were reported with a frequency of less than 1 in 100 patients but a causal relationship between pirbuterol and the reaction could not be determined: migraine, productive cough, wheezing, and dermatitis.

The following rates of adverse reactions during three-month controlled clinical trials involving 310 patients are noted. The table does not include mild reactions.


Reaction Pirbuterol Metaproterenol
N=157 N=153
Central Nervous System
  tremors 1.3% 3.3%
  nervousness 4.5% 2.6%
  headache 1.3% 2.0%
  weakness .0% 1.3%
  drowsiness .0% 0.7%
  dizziness 0.6% .0%
  palpitations 1.3% 1.3%
  tachycardia 1.3% 2.0%
  chest pain/tightness 1.3% .0%
  cough .0% 0.7%
  nausea 1.3% 2.0%
  diarrhea 1.3% 0.7%
  dry mouth 1.3% 1.3%
  vomiting .0% 0.7%
  skin reaction .0% 0.7%
  rash .0% 1.3%
  bruising 0.6% .0%
  smell/taste change 0.6% .0%
  backache .0% 0.7%
  fatigue .0% 0.7%
  hoarseness .0% 0.7%
  nasal congestion .0% 0.7%

Electrocardiograms: Electrocardiograms, obtained during a randomized, double-blind, crossover study in 57 patients, showed no observations or findings considered clinically significant, or related to drug administration. Most electrocardiographic observations, obtained during a randomized, double-blind, cross-over study in 40 patients, were judged not clinically significant or related to drug administration. One patient was noted to have some changes on the one hour postdose electrocardiogram consisting of ST and T wave abnormality suggesting possible inferior ischemia. This abnormality was not observed on the predose or the six hours postdose ECG. A treadmill was subsequently performed and all the findings were normal.