Pirbuterol

Pronunciation

(peer BYOO ter ole)

Index Terms

• Maxair Autohaler
• Pirbuterol Acetate

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Aerosol Breath Activated, Inhalation, as acetate:

Maxair Autohaler: 200 mcg/INH (14 g [DSC])

Brand Names: U.S.

• Maxair Autohaler [DSC]

Pharmacologic Category

• Beta₂ Agonist

Pharmacology

Pirbuterol is a beta₂-adrenergic agonist with a similar structure to albuterol, specifically a pyridine ring has been substituted for the benzene ring in albuterol. The increased beta₂ selectivity of pirbuterol results from the substitution of a tertiary butyl group on the nitrogen of the side chain, which additionally imparts resistance of pirbuterol to degradation by monoamine oxidase and provides a lengthened duration of action in comparison to the less selective beta-agonist agents.

Metabolism

Hepatic (by sulfate conjugation)

Excretion

Urine (10% as unchanged drug; 51% as pirbuterol plus its sulfate conjugate)

Onset of Action

5 minutes; Peak effect: Therapeutic: 0.5 to 1 hour

Duration of Action

5 hours

Half-Life Elimination

~2 hours

Use: Labeled Indications

Prevention and treatment of reversible bronchospasm including asthma

Contraindications

Hypersensitivity to pirbuterol or any component of the formulation

Dosing: Adult

Note: Maxair Autohaler has been discontinued in the US for more than 1 year.

Bronchospasm, prevention and treatment: Inhalation: 1 to 2 inhalations every 4 to 6 hours; not to exceed 12 inhalations daily. Patients should be advised to promptly consult healthcare provider or seek medical attention if no relief from acute treatment

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Bronchospasm, prevention and treatment: Children ≥12 years and Adolescents: Inhalation: Refer to adult dosing.

Dosing: Renal Impairment

No dosage adjustment provided in manufacturer’s labeling. However, dosage adjustment unlikely due to low systemic absorption.

Dosing: Hepatic Impairment

No dosage adjustment provided in manufacturer’s labeling. However, dosage adjustment unlikely due to low systemic absorption.

Administration

Inhalation: Metered-dose inhaler: Shake well before use; prime prior to first use, and whenever inhaler has not been used for >48 hours by releasing 2 test sprays into the air (away from face). Inhaler should be cleaned with a clean, dry cloth (mouthpiece) and a dry cotton swab (spray hole) at least once per week.

Storage

Store between 15°C and 30°C (59°F and 86°F).

Drug Interactions

AtoMOXetine: May enhance the tachycardic effect of Beta2-Agonists. Monitor therapy

AtoMOXetine: May enhance the hypertensive effect of Sympathomimetics. AtoMOXetine may enhance the tachycardic effect of Sympathomimetics. Monitor therapy

Atosiban: Beta2-Agonists may enhance the adverse/toxic effect of Atosiban. Specifically, there may be an increased risk for pulmonary edema and/or dyspnea. Monitor therapy

Beta-Blockers (Beta1 Selective): May diminish the bronchodilatory effect of Beta2-Agonists. Of particular concern with nonselective beta-blockers or higher doses of the beta1 selective beta-blockers. Monitor therapy

Beta-Blockers (Nonselective): May diminish the bronchodilatory effect of Beta2-Agonists. Avoid combination

Betahistine: May diminish the therapeutic effect of Beta2-Agonists. Monitor therapy

Cannabinoid-Containing Products: May enhance the tachycardic effect of Sympathomimetics. Exceptions: Cannabidiol. Monitor therapy

Cocaine: May enhance the hypertensive effect of Sympathomimetics. Management: Consider alternatives to use of this combination when possible. Monitor closely for substantially increased blood pressure or heart rate and for any evidence of myocardial ischemia with concurrent use. Consider therapy modification

Doxofylline: Sympathomimetics may enhance the adverse/toxic effect of Doxofylline. Monitor therapy

Guanethidine: May enhance the arrhythmogenic effect of Sympathomimetics. Guanethidine may enhance the hypertensive effect of Sympathomimetics. Monitor therapy

Iobenguane I 123: Sympathomimetics may diminish the therapeutic effect of Iobenguane I 123. Avoid combination

Linezolid: May enhance the hypertensive effect of Sympathomimetics. Management: Reduce initial doses of sympathomimetic agents, and closely monitor for enhanced pressor response, in patients receiving linezolid. Specific dose adjustment recommendations are not presently available. Consider therapy modification

Loop Diuretics: Beta2-Agonists may enhance the hypokalemic effect of Loop Diuretics. Monitor therapy

Loxapine: Agents to Treat Airway Disease may enhance the adverse/toxic effect of Loxapine. More specifically, the use of Agents to Treat Airway Disease is likely a marker of patients who are likely at a greater risk for experiencing significant bronchospasm from use of inhaled loxapine. Management: This is specific to the Adasuve brand of loxapine, which is an inhaled formulation. This does not apply to non-inhaled formulations of loxapine. Avoid combination

MAO Inhibitors: May enhance the adverse/toxic effect of Beta2-Agonists. Monitor therapy

Sympathomimetics: May enhance the adverse/toxic effect of other Sympathomimetics. Monitor therapy

Tedizolid: May enhance the hypertensive effect of Sympathomimetics. Tedizolid may enhance the tachycardic effect of Sympathomimetics. Monitor therapy

Thiazide and Thiazide-Like Diuretics: Beta2-Agonists may enhance the hypokalemic effect of Thiazide and Thiazide-Like Diuretics. Monitor therapy

Tricyclic Antidepressants: May enhance the adverse/toxic effect of Beta2-Agonists. Monitor therapy

Adverse Reactions

1% to 10%:

Cardiovascular: Palpitations (2%), tachycardia (1%)

Central nervous system: Nervousness (7%), tremor (6%), headache (2%), dizziness (1%)

Endocrine & metabolic: Decreased serum potassium, increased serum glucose

Gastrointestinal: Nausea (2%)

Respiratory: Cough (1%)

<1% (Limited to important or life-threatening): Chest pain, confusion, depression, hypotension, insomnia, numbness of extremities, pruritus, skin rash, sore throat, syncope

Warnings/Precautions

Concerns related to adverse effects:

• Bronchospasm: Rarely, paradoxical bronchospasm may occur with use of inhaled bronchodilating agents (may occur more frequently with the first use of a new canister); this should be distinguished from inadequate response.

Disease-related concerns:

• Asthma: Appropriate use: Optimize anti-inflammatory treatment before initiating maintenance treatment with pirbuterol. Do not use as a component of chronic therapy without an anti-inflammatory agent. Only the mildest forms of asthma (Step 1 and/or exercise-induced) would not require concurrent use based upon asthma guidelines.

• Cardiovascular disease: Use with caution in patients with cardiovascular disease (arrhythmia or hypertension or heart failure); beta-agonists may cause elevation in blood pressure, heart rate and result in CNS stimulation/excitation. Beta₂-agonists may also increase risk of arrhythmias.

• Diabetes: Use with caution in patients with diabetes mellitus; beta₂-agonists may increase serum glucose.

• Glaucoma: Use with caution in patients with glaucoma; may elevate intraocular pressure.

• Hyperthyroidism: Use with caution in hyperthyroidism; may stimulate thyroid activity.

• Hypokalemia: Use with caution in patients with hypokalemia; beta₂-agonists may decrease serum potassium.

• Seizures: Use with caution in patients with seizure disorders; beta-agonists may result in CNS stimulation/excitation.

Other warnings/precautions:

• Appropriate use: Do not exceed recommended dose; serious adverse events, including fatalities, have been associated with excessive use of inhaled sympathomimetics.

• Patient information: Patients must be instructed to seek medical attention in cases where acute symptoms are not relieved or a previous level of response is diminished. The need to increase frequency of use may indicate deterioration of asthma, and treatment must not be delayed. All patients should utilize a spacer device when using a metered-dose inhaler.

Monitoring Parameters

Respiratory rate; FEV₁, peak flow, and/or other pulmonary function tests; blood pressure, heart rate; CNS stimulation; serum glucose, serum potassium

Pregnancy Risk Factor

C

Pregnancy Considerations

Adverse events have been observed in some animal reproduction studies. Beta-agonists may interfere with uterine contractility if administered during labor.

Uncontrolled asthma is associated with adverse events on pregnancy (increased risk of perinatal mortality, pre-eclampsia, preterm birth, low birth weight infants). Other beta₂-receptor agonists are preferred for the treatment of asthma during pregnancy (NAEPP, 2005).