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Why Does Quinidine Cause Diarrhea?

Maya Lin-Takahashi • • 6 min read
Why Does Quinidine Cause Diarrhea?

In conclusion, the present evidence suggests that the diarrhea caused by class I antiarrhythmic drugs

antiarrhythmic drugs
Class I antiarrhythmics are fast sodium channel blockers. They are responsible for phase 0 of fast-response cardiac action potentials. The three subclasses differ in their efficacy for reducing the slope of phase 0, with Ic drugs having the greatest and Ib drugs having the smallest effect on phase 0.
such as quinidine and propafenone is a result of a reduction in basolateral K+ conductance and inhibition of BK(Ca) channels, thereby impeding transepithelial Na+ and water absorption.

How does quinidine cause arrhythmia?

Mechanism of action

Like all other class I antiarrhythmic agents, quinidine primarily works by blocking the fast inward sodium current (INa). Quinidine's effect on INa is known as a 'use dependent block'. This means at higher heart rates, the block increases, while at lower heart rates, the block decreases.

What is the adverse effect of quinidine?

Diarrhea, nausea, vomiting, loss of appetite, stomach pain/cramps, or a burning feeling in throat or chest (e.g., heartburn) may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Maya Lin-Takahashi
Author

Maya Lin-Takahashi

Maya is a hardware enthusiast who tests and reviews smart home devices, smartphones, wearables, and audio gear. She focuses on practical consumer value and build quality.