A known case of COPD is on treatment with theophylline. Which of the following side effect will be commonly seen due to inhibition of PDE4?

The most common side effects are headache, nausea, and vomiting (due to inhibition of PDE4), abdominal discomfo, and restlessness. There may also be increased acid secretion (due to PDE inhibition) and diuresis (due to inhibition of adenosine A1 receptors). At high concentrations, cardiac arrhythmias may occur as a consequence of inhibition of cardiac PDE3 inhibition and antagonism of cardiac A1 receptors. At very high concentrations, seizures may occur due to central A1 receptor antagonism. Ref: Barnes P.J. (2011). Chapter 36. Pulmonary Pharmacology. In L.L. Brunton, B.A. Chabner, B.C. Knollmann (Eds), Goodman & Gilman's The Pharmacological Basis of Therapeutics, 12e.