Cyclobenzaprine Extended-Release Capsules and Terbutaline Sulfate

• Generic Name: cyclobenzaprine
• Dosage Forms: n.a.
• Other Brand Names: Amrix, Comfort Pac with Cyclobenzaprine, Fexmid, Flexeril

• It is used to relax muscles.

• Generic Name: terbutaline
• Dosage Forms: n.a.
• Other Brand Names: Brethine

Symptomatic management or prevention of bronchospasm in patients with reversible, obstructive airway disease (e.g., asthma).

Some experts suggest use of oral β2-adrenergic agonist therapy principally in patients unable to use inhaled bronchodilators (e.g., young children). Other experts do not recommend oral β2-agonists for relief of acute asthma symptoms. Oral administration associated with slower onset of action and increased incidence of adverse effects.

Sub-Q terbutaline reserved for prehospital management of severe asthma exacerbations when inhaled β2-selective agents are not readily available. Sub-Q terbutaline not used routinely for treatment of severe exacerbations of asthma in hospitalized patients. No proven advantage of sub-Q administration compared with oral inhalation (no longer commercially available in US).

Symptomatic management of reversible bronchospasm associated with chronic bronchitis and emphysema.

Inhaled β2-adrenergic agonists preferred over oral β2-adrenergic agonist therapy for treatment of COPD; long-acting inhaled bronchodilators more effective and convenient than short-acting agents. Oral β2-adrenergic agonist use associated with slower onset of action and increased incidence of adverse effects compared with inhaled therapy.

Role of oral β2-adrenergic agonists in treatment of COPD limited.

Has been used for acute IV or sub-Q therapy in selected women to inhibit uterine contractions in preterm labor (tocolysis) and prolong gestation when beneficial.

Manufacturers and FDA warn that injection is not FDA labeled for and is contraindicated for prolonged tocolysis (beyond 48–72 hours), because of the potential for serious maternal cardiac effects and death. (See Preterm Labor under Cautions.)

Manufacturers and FDA also warn that oral tablets are not FDA labeled for and are contraindicated for acute or maintenance tocolysis, because efficacy not proven and safety concerns similar to injection. (See Preterm Labor under Cautions.)

Do not use terbutaline sulfate (injection or oral tablets) for maintenance tocolysis, particularly in the outpatient or home setting. (See Preterm Labor under Cautions.)

However, available data suggest that acute β-adrenergic agonist treatment may forestall labor for 48 hours, providing time for patients to be transferred to other (e.g., tertiary-care) facilities and/or receive corticosteroids to increase fetal lung maturation. Any other potential benefits of such drugs in prolonging pregnancy are unclear.

ACOG states that because of conflicting results, there is no clear first-line tocolytic agent.