**Core Concept**
Theophylline is a methylxanthine derivative used in the management of asthma and COPD. It acts as a phosphodiesterase inhibitor, thereby increasing cAMP levels and relaxing smooth muscle. However, its narrow therapeutic index and potential for toxicity necessitates careful monitoring.

**Why the Correct Answer is Right**
Theophylline overdose can lead to a range of systemic effects, primarily due to its inhibition of cytochrome P450 enzymes and subsequent accumulation of toxic metabolites. The primary toxic effects of theophylline include:

* Increased sympathetic activity, leading to tachycardia, hypertension, and cardiac arrhythmias
* Central nervous system (CNS) stimulation, resulting in anxiety, restlessness, and seizures
* Diuresis and hypokalemia due to its diuretic effects

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect because theophylline does not typically cause hepatotoxicity at therapeutic doses. While it can cause liver enzyme elevations, severe hepatotoxicity is rare.

**Option B:**
This option is incorrect because theophylline does not primarily cause cardiac ischemia. While it can cause cardiac arrhythmias, the primary mechanism is related to its sympathetic effects rather than direct myocardial ischemia.

**Option C:**
This option is incorrect because theophylline does not typically cause hypoglycemia. In fact, it can cause hyperglycemia due to its effects on glycogenolysis and gluconeogenesis.

**Clinical Pearl / High-Yield Fact**
Theophylline has a narrow therapeutic index, and levels above 20 mg/L can increase the risk of toxicity. Regular monitoring of serum theophylline levels is essential in patients receiving this medication.

**Correct Answer: C. Diuresis and hypokalemia due to its diuretic effects.**