Risperidone increases the risk of :
**Core Concept**
Risperidone is an atypical antipsychotic medication primarily used to treat schizophrenia and bipolar disorder. Its mechanism of action involves antagonism of dopamine D2 receptors, serotonin 5-HT2A receptors, and norepinephrine α1 and α2 receptors, which contributes to its therapeutic effects and side-effect profile.
**Why the Correct Answer is Right**
The correct answer is related to risperidone's potential to cause QT interval prolongation, a cardiac arrhythmia risk factor. This is due to its blockade of potassium channels, particularly the hERG channel, which is responsible for the rapid component of the delayed rectifier potassium current (IKr). By blocking this channel, risperidone increases the duration of the QT interval, thereby increasing the risk of torsades de pointes, a potentially life-threatening arrhythmia.
**Why Each Wrong Option is Incorrect**
* **Option A:** While risperidone can cause orthostatic hypotension due to its α1 receptor blockade, this is not the most significant risk factor.
* **Option B:** Risperidone is not primarily associated with an increased risk of agranulocytosis, a condition more commonly linked to clozapine.
* **Option C:** Although risperidone can cause weight gain and metabolic changes, it is not specifically known for increasing the risk of type 2 diabetes.
**Clinical Pearl / High-Yield Fact**
When prescribing atypical antipsychotics like risperidone, it's essential to monitor patients for signs of QT interval prolongation, such as prolonged QTc intervals on the electrocardiogram, and to consider concomitant medications that may further increase this risk.
**Correct Answer: D. QT interval prolongation**