<prompt> Which of the following statements about theophylline is TRUEIts use in asthma has declined because of narrow safety marginIts dose needs to be reduced in the smokersIt acts by increasing the formation of cAMPIts plasma half life is longer in children as compared to that in adults  <response>: Theophylline has a narrow therapeutic index. Its use has been declined due to narrow safety margin.It inhibits the enzyme phosphodiesterase and thus decreases the metabolism of cAMP. It does not increase the formation of cAMP.Smoking is a powerful enzyme inducer. Dose of theophylline should be increased in smokers.Children metabolize theophylline faster than adults whereas elderly metabolize it slowly. Therefore, the half-life of theophylline is shorter in children as compared to adults. 