<prompt> All of the following statements regarding theophylline are true, except:Increases cAMPInhibits phosphodiesteraseIncrease in dose is required in smokersIncrease in dose is required in cardiopulmonary disease  <response>: Theophylline is a methylxanthine, used in the treatment of bronchial asthma. Its dose has to be reduced in elderly age 60 years, in congestive hea failure, pneumonia and liver failure. 