Air and Breathing
Asthma & Drugs
The three asthma treatment choices are:
A shift in treatment strategy has occurred in the past decade toward prevention and primary treatment of asthma with blocking medications taken orally and inhaled steroids. Previously, drug treatment relied on bronchodilator drugs that dilate the small tubes in the lung which constrict during an asthma attack; these drugs relieve the wheezing and shortness of breath quickly. Many patients inhaled bronchodilators continuously and relied on them to control their asthma This is symptomatic therapy which does not address the cause or mechanisms of the asthma. Better treatment strategies emphasize drugs which prevent the allergic response or treat the inflammation that keeps asthma going.
Major classes of asthma medications
Drug treatment strategies have shifted away from drugs which relax smooth muscle and dilate the branching tubes in the lung to drugs which block allergic reactions and reduce inflammation.
Cromoglycate (Intal, fivent) or nedocromil (Tilade) by inhalation or ketotifen (Zaditen) orally have been favored to block allergic reactions as preventative measures. Ketotifen is an antihistamine that block other mediators of the inflammatory response such as tumor necrosis factor and can be taken once or twice daily as a preventive medication; it is approved in Canada for the preventative treatment of asthma in children.
Inhaled steroids (Flovent, Pulmicort) have become "first line of defense" in treating chronic asthma.
The bronchodilators (e.g. ventolin, bricanyl, berotec, salmeterol) are used to treat the acute wheezing attacks, along with steroids which block the delayed inflammatory swelling effects. Since it is possible that the bronchodilator sprays make asthma worse in the long run, their use should be limited.
Antileukotrienes (montelukast, zafirlukast, zileuton)
Taking orally these agents inhibit leukotrienes, mediators of the inflammatory response. Their potential use is not well-defined but is considered to be preventive medication taken on a daily basis to prevent the early stages of an inflammatory response. Zafirlukast (Accolate) is taken as 20mg tablets twice daily. Montelukast (Singulair) has been studied in children ( 6 -14 years of age) and adults; taken once a day, the most favorable results are a 37% reduction in the frequency of asthma attacks; 30 % had no response to the drug.
Prednisone orally is prescribed if the asthma eludes control by inhaled steroids.
Metered Dose Inhalers (MDI)
The mainstay of asthma treatment has been drugs delivered into the lungs through pressurized inhalers - a metered doses of the drug was supposed to be delivered with each press of the inhaler trigger. There have always been problems with this methods of drug deliver and they are poised to be replaced in the US and Canada in 98 and 99. The irony is that cholorohydrocarbons were uses as propellants and these substances have been banned to protect the ozone layer. Some of the MDIs have been reformulated with other propellants.
The other major problem with MDIs wasan unreliable delivery of drug to the lungs - even when used properly, up to 2/3's of the drug dose would end up in the throat, esophagus and stomach. The MDI user would have to be skilled in coordinating inhalation with squeezing the MDI trigger to get the drug into the lungs. As the MDI approached empty, the dose delivered would decrease and the user would not know.
MDIs are replaced with powder inhalers that are breath actuated - they depend on the user's inhalation to get the drug into the lungs. Intal has always been available with a "spinhaler" delivery and Ventolin Rotohaler has been in use for some time. In Canada, the steroid, budesonide, has been available for several years as a powder inhaler (Pulmicort Turbuhaler). Pulmicort has been y effective; the only disadvantage is that the inhaled powder is so fine that users do not notice drug inhalation. GlaxoWellcome has introduced their steroid medication, fluticasone*, in a newly designed powder inhaler - the FloVent Diskus and their long-acting bronchodilator, salmeterol, as the SereVent Diskus. The diskus design has addresses some problems with powder inhalers and comes with a dose counter and lactose has been added provide more of a sensation that the powder is being inhaled. Flovent is also available as a metered dose inhaler. * Sept. 1999 fluticasone replaced the once popular steroid inhaler, Beclovent and Becloforte