Inhaled bronchodilators are the primary medications used, and result in a small overall benefit. The two major types are β2 agonists and anticholinergics; both exist in long-acting and short-acting forms. They reduce shortness of breath, wheeze, and exercise limitation, resulting in an improved quality of life. It is unclear if they change the progression of the underlying disease.In those with mild disease, short-acting agents are recommended on an as needed basis. In those with more severe disease, long-acting agents are recommended. Long-acting agents partly work by reducing hyperinflation. If long-acting bronchodilators are insufficient, then inhaled corticosteroids are typically added. Which type of long-acting agent, tiotropium (a long-acting anticholinergic) or a long-acting beta agonist (LABA) is better is unclear, and trying each and continuing with the one that works best may be advisable. Both types of agent appear to reduce the risk of acute exacerbations by 15–25%. While both may be used at the same time, any added benefit is of questionable significance.Several short-acting β2 agonists are available, including salbutamol (albuterol) and terbutaline. They provide some relief of symptoms for four to six hours. LABAs such as salmeterol, formoterol, and indacaterol are often used as maintenance therapy. Some feel the evidence of benefits is limited, while others view the evidence of benefit as established. Long-term use appears safe in COPD with adverse effects include shakiness and heart palpitations. When used with inhaled steroids they increase the risk of pneumonia. While steroids and LABAs may work better together, it is unclear if this slight benefit outweighs the increased risks. There is some evidence that combined treatment of LABAs with long-acting muscarinic antagonists (LAMA), an anticholinergic, may result in less exacerbations, less pneumonia, an improvement in forced expiratory volume (FEV1%), and potential improvements in quality of life when compared to treatment with LABA and an inhaled corticosteriod (ICS). All three together, LABA, LAMA, and ICS, have some evidence of benefits. Indacaterol requires an inhaled dose once a day, and is as effective as the other long-acting β2 agonist drugs that require twice-daily dosing for people with stable COPD.Two main anticholinergics are used in COPD, ipratropium and tiotropium. Ipratropium is a short-acting agent, while tiotropium is long-acting. Tiotropium is associated with a decrease in exacerbations and improved quality of life, and tiotropium provides those benefits better than ipratropium. It does not appear to affect mortality or the overall hospitalization rate. Anticholinergics can cause dry mouth and urinary tract symptoms. They are also associated with increased risk of heart disease and stroke. Aclidinium, another long-acting agent, reduces hospitalizations associated with COPD and improves quality of life. The LAMA umeclidinium bromide is another anticholinergic alternative. When compared to tiotropium, the LAMAs aclidinium, glycopyrronium, and umeclidinium appear to have a similar level of efficacy; with all four being more effective than placebo. Further research is needed comparing aclidinium to tiotropium.

Question: what are the two major types of asthma?
Answer: β2 agonists and anticholinergics

Question: What is the duration of time that agonists are potent for?
Answer: four to six hours