For ziprasidone, which baseline labs are recommended for at-risk individuals or those on diuretics?

• A. Baseline serum K and Mg
• B. Baseline liver enzymes
• C. Baseline calcium
• D. No labs required

Answer: (A)

The main concept here is identifying factors that influence QT interval risk with ziprasidone. QT prolongation can lead to dangerous arrhythmias, and electrolyte disturbances—especially low potassium (hypokalemia) and low magnesium (hypomagnesemia)—exacerbate this risk. People taking diuretics are more prone to losing these electrolytes, so checking baseline serum potassium and magnesium helps detect and correct deficiencies before starting ziprasidone, reducing the chance of QT-related problems during treatment.

Baseline liver enzymes aren’t chosen because they don’t directly predict QT risk, though liver function can affect drug metabolism in other contexts. Baseline calcium isn’t the key determinant of QT risk in this scenario, and saying no labs are required would miss an important safety step for those at risk.