Cinchonism, quinidine causing

Quinidine causes cinchonism (headache, vertigo, tinnitus) cardiac depression gastrointestinal upset and allergic reactions (eg, thrombocytopenic purpura). As noted in Chapter 13, quinidine reduces the clearance of digoxin and may increase the serum concentration of the glycoside to dangerous levels. Procainamide causes hypotension (especially when used parenterally) and a reversible syndrome similar to lupus erythematosus. Disopyramide has... 

Answer D. The symptoms described are those of cinchonism, which usually include tinnitus and, when more severe, CNS effects including hallucinations. Cinchonism is characteristic of quinidine and its optical isomer, the antimalarial drug quinine. Like most antiarrhythmic drugs, quinidine can cause cardiac arrhythmias heralded by the ECG changes described. 

C. Other effects. Quinidine commonly causes nausea, vomiting, and diarrhea after acute ingestion and, especially with chronic doses, cinchonism (tinnitus, vertigo, deafness, or visual disturbances). Procainamide may cause gastrointestinal upset and, with chronic therapy, a lupus-like syndrome. 

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