Montelukast (Singulair): Drug Whys

A selective leukotriene receptor antagonist, Montelukast's competitive activity is associated with reduced bronchospasm and lessened airway smooth muscle contraction

Generic Name: Montelukast (no generic available, U.S. patent expires August 2012)
Common Brand Name: Singulair® (Merck & Company – U.S.)
Popularity: 24th most commonly prescribed drug between 2002-2009 (U.S.)
Class: Anti-inflammatory, leukotriene inhibitor (also known as leukotriene receptor antagonist or LTRA)

Treatment Uses — For treatment of asthma, prophylaxis (i.e., prevention) against exercise-induced asthma, and perennial and seasonal allergic rhinitis (runny nose). May be effective for prophylaxis against aspirin-induced asthma (AIA), discovered when treating rhinitis is asthma patients who occasionally present with a triad of asthma, aspirin sensitivity, and nasal polyps (hence rhinitis).

May be helpful in cases of atopic dermatitis and eosinophilic gastroenteritis. Montelukast does not work and is not indicated for reversal of bronchospasm in acute asthma attacks, including status asthmaticus or acute bronchiolitis (in pediatric patients). May have some benefit in prophylaxis against certain migraine headaches and possibly in treatment of urticaria. Montelukast has been studied and shown not effective at reducing symptoms of dysmenorrhea.

EMS providers commonly use beta2 agonists such as albuterol (and perhaps anticholinergic agents like ipratropium) used to manage acute bronchospasm. Long term control of recurrent asthma symptoms is best accomplished with inhaled corticosteroids (ICS) as first-line therapy.

ICS include medications such as Flovent®, Azmacort®, QVAR ®, etc. Use of ICS is emphasized in treatment guidelines published by the National Asthma Education and Prevention Program (NAEPP) and the National Institutes of Health, (NIH) National, Heart, Lung, Blood Institute (NHLBI) and includes both children and adults.

When LTRAs first hit the market, many believed they would revolutionize asthma treatment and quickly jump to first line therapy. While conceptually LTRAs seem ideal (most nasty asthma effects are mediated by leukotriene receptor activation), widespread use has shown considerable variability in individual patient response.

The current challenge is best identifying patients who will benefit from LTRAs. Long acting beta agonists (LABAs), which are sustained action versions of beta agonists used in emergencies, hit the market with similar vigor, but have also failed to capture first line recommendation for asthma management.

In fact, LABA use may increase risk of asthma related deaths even when used in conjunction with currently recommended meds. At the recommendation of the FDA (Food and Drug Administration), prescribers have backed away from LABAs except in situations where asthma remains poorly controlled with ICS and other asthma-controller meds.

Dosing and Administration — The recommended dose of montelukast for asthma, or perennial and seasonal allergic rhinitis in adults and children aged 15 and older, is 10 milligrams orally, taken each evening. There is no added advantage to daily doses over 10 milligrams. For exercise-induced asthma in adults and children over 15, the recommended dose is 10 milligrams taken orally at least two hours prior to exercise.

Additional doses should not be taken within 24 hours and patients using daily dosing for another indication should not take additional doses to prevent exercise-induced asthma. Any patient with asthma or reactive airway disease of any kind should always have a short acting beta agonist (such as albuterol) available as a rescue medication.

For children aged 6 to 14 years, the recommended daily oral dosing for all indications is 5 milligrams and for children from 2 to 5 years, 4 milligrams. One 4 milligram packet of montelukast granules is recommended for children aged 6 to 23 months, given once daily. As with adults, all pediatric doses should be taken in the evening.

Montelukast comes in 10 milligram oral tablets which should not be broken, crushed or chewed. It also comes in 4 and 5 milligram chewable oral tablets and a 4 milligram oral granules packet. The oral granules can be given directly into the mouth or mixed with room temperature or cold, soft foods including applesauce, carrots, rice or ice cream.

For infants, the granules can be mixed with breast milk or formula. Granules should not be dissolved in any other liquids. Stability when mixed with other foods is unknown.

Food does not interfere with absorption of montelukast but does decrease available drug by 10 percent. Studies have clearly shown best results fare achieved when montelukast is taken in a single daily dose during evening hours.

Dosage adjustments do not appear necessary in older patients, persons with mild-to-moderate liver failure or in patients with kidney disease.

Overdoses in humans of up to 1,000 milligrams have been reported without fatalities or serious adverse effects. The most common symptoms associated with overdoses have been abdominal pain, sleepiness, headache, dizziness, thirst, vomiting and psychomotor hyperactivity. Studies of up to 5,000 milligrams per kilogram in mice produced no fatalities. It is unknown whether montelukast is removed by dialysis. Treatment of overdoses should be supportive.

Pharmacology/Pharmacokinetics/Stability — Following oral administration, initial effects of montelukast are seen in three to four hours, with peak blood levels seen between two and four hours. Effects continue for up to 24 hours.

Montelukast is metabolized extensively in the liver. Nearly all of montelukast (86 percent) is excreted in the feces with a very small quantity (0.2 percent) excreted in urine.

The safety of montelukast in pregnant women has not been studied sufficiently. Human studies to date have not shown any association with increased risk of adverse perinatal effects associated with LTRAs. Studies in animals have not shown any direct harmful effects on fetuses.

Until more is known, montelukast should be used during pregnancy only when benefits outweigh potential fetal risks. Montelukast is excreted in the breast milk of lactating rats; no human studies have been conducted. Infant risk, therefore, cannot be ruled out – caution is advised when breastfeeding.

Montelukast is a selective leukotriene receptor antagonist whose competitive activity is associated with reduced bronchospasm, lessened airway smooth muscle contractions, and reduction in inflammatory processes.

Montelukast 10 milligram film-coated tablets are beige, square-shaped with code number MRK 117 on one side. The 5 milligram chewable tablets are pink, round tablets with code MRK 275 on one side. The 3 milligram chewable tablets are pink, oval tablets with MRK 711 on one side.

All tablets have SINGULAIR embossed on the side opposite the pill code. The 4 milligram packet contains white granules in a foil child-resistant packet. Montelukast should be stored at room temperature (77 F), with excursions permitted between 59 to 86F.

Cautions and Warnings — The most important caution for patients with asthma is to reinforce that montelukast is not effective for reversing bronchospasm in acute asthma attacks. All patients with reactive airway disease should have an appropriate rescue medication available (such as a short acting beta agonist).

Note that LABAs such as Serevent® are not indicated for acute asthma attacks either. EMS services that have armed their members with knowledge and patient informational brochures describing appropriate medical management of asthma have not only reduced frequent fliers with acute asthma attacks, but saved lives by directing asthma patients to discuss their medication regimens with their prescribers.

Important Side Effects and Interactions — Abdominal pain (2.9 percent), rash (2 percent), GI upset/nausea/diarrhea (2 percent) and dizziness (1.9 percent) have been the most commonly reported side effects associated with montelukast. Headache had a reported 18.4 percent incidence in drug trials but also occurred in 18.1 percent of patients given placebo. Headache has not been recognized as a common side effect in any other studies of montelukast.

Two sets of side effects, although rare, are worth noting for reference. Neuropsychiatric effects that may be drug related including agitation, aggressive behavior, depression, and suicide have been reported. Patients and clinicians should be alert to the occurrence of any neuropsychiatric symptoms. Additionally, even rarer but equally troubling have been occasional reports of a systemic inflammatory condition known as Churg-Strauss syndrome that may or may not be drug related.

Currently, there are five drugs reported to interact with montelukast. Of these, none are significant to prehospital and emergency medicine providers.

Average Costs – U.S.
• 10 mg tablet (brand name Singulair)*
Patient cost: $5.37 each
Large Hospital cost: $3.99 each
*(Wal Mart® and Target don’t include this med in their $4/month programs)

1. MICROMEDEX® Healthcare Series: Thomson Micromedex, Greenwood Village, Colorado (accessed October, 2010).
2. Albany Medical Center Pharmacy, Albany, New York.

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