Asthma Medicines

The B-adrenergic agonists available in tablet or elixir form are not for emergency use since they have slow onsets of action (up to one hour). Albuterol, terbutaline, and metaproterenol are available as oral medications. Since they are absorbed into the bloodstream in greater quantity than the inhaled form, there are greater chances of side effects. These include tremors, muscle cramps, nervousness, insomnia, and palpitations. The long-acting oral preparations of albuterol have proved useful for patients with nocturnal asthma, although the long-acting aerosol sprays that have become available also have been effective in this setting. Those patients who have difficulty using a metered-dose inhaler may benefit from the oral preparations.

Another potential advantage of oral preparations is that the medication carried in the blood may reach small bronchial tubes that may not have been reached by inhalation. These small airways are often inflamed and swollen in moderate and severe asthma and receive only a relatively small percentage of the medication inhaled. In addition, there may be thick mucus “plugs” that block the air passages. Aerosol medication may therefore be primarily distributed to the larger, more open passages which receive greater airflow on inhalation. It is conceivable, however, that medication deposited in these larger passages may be absorbed into blood vessels and reach the blood circulation, thereby eventually reaching the smaller airways.

In the asthmatic patient who does not appear to respond fully to aerosol medication, trial with an oral preparation is indicated. Peak flows or spirometry may be performed after a suitable trial of one to two weeks. If flow rates have increased and symptoms have diminished, then the oral preparation of the B2-adrenergic agonist may be used in conjunction with the aerosol. A drawback to this approach will be the greater likelihood of adverse effects from the increased absorption of the B-agonist. Of note, however, is that tolerance to these effects often develops after several days of use. Unfortunately, the elderly population with asthma may be adversely affected more than younger patients. Tremors may be especially severe in older patients. These patients are also more likely to have preexisting cardiac conditions that may increase the risk of adverse effects such as rapid or irregular heart rhythms.

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