Do Fluoroquinolones Prolong QT Interval?

Quinolones have been in the medical market since a very long time. Modern day quinolones are known as Fluoroquinolones. They are an important class of antibiotics in the medical world. Fluoroquinolones are broad spectrum antibacterial agents, with a significant ability to treat both gram positive and gram-negative bacteria. However, their best effect is seen while treating the gram-negative bacteria. Fluoroquinolones are successfully and widely used to treat many urinary tract infections, gastrointestinal infections and respiratory tract infections. Some of the commonly prescribed fluoroquinolones are ciprofloxacin, ofloxacin, norfloxacin and levofloxacin.

Fluoroquinolones work by interfering in the process of DNA replication. However, though they are such a great option for treating a wide variety of infections, they are known for their rapid onset of resistance. Hence, they are usually reserved as a second or third line of treatment by most physicians.

Do Fluoroquinolones Prolong QT Interval?

Fluoroquinolones are a generally well tolerated set of medicines in most of the people. However, they are seen to prolong the QT interval in some individuals. This effect is mostly seen with the use of moxifloxacin. Hence, they have to be carefully administered in people taking any anti-depressants, or any medicines related to the cardiac disorders, as these can increase the risk of prolonged QT interval.

QT Interval

A QT interval is the time duration measured from the start of the Q wave to the end of the T wave, on an ECG. An ECG is a pictorial graph used to represent the process of conduction system of the heart on the paper. This graph is used by the physician to evaluate the health of the heart and gauge any potential harmful findings. The heart follows a complex electrical cycle. This cycle includes a careful contraction and relaxation of the left and right atrium and the left and right ventricles. By way of this mechanism, the left and right atriums contract first and then left and the right ventricles contract, thus pumping the blood to the various parts of the body. This is a very complex phenomenon and is very carefully carried out by the body. The QT interval represents the depolarization and repolarization of the ventricles of the heart. The electrical activity of the heart is measured by an electrocardiogram, also known commonly as ECG. When the heart beats, with its every beat, an electrical signal is sent from the top of the heart to its bottom. This results in contraction and relaxation of atriums and ventricles in the heart, thereby resulting in programmed and an organized pumping of blood from the heart to the whole body. This whole activity is recorded in an ECG. There are five electrical waves for each heartbeat-p, q, r, s and t. all this is recorded on a graph, and a detailed study of this graph can help a physician determine the hearts electrical activity and find any abnormalities in it. This helps in preventing and curing many heart related issues that can otherwise prove to be fatal.

This programmed and organized activity of the heart’s contraction and relaxation can be disturbed by many reasons. Some factors like congenital heart disease, a history in the family for congenital heart disease, renal failure, cardiac failure, exercise and stress, as well as certain medicines are some of the risk factors that can cause a disturbance in this electrical activity. As a result, the functioning of the heart gets compromised. And the pumping action of the heart can be severely disturbed.

This disturbance in the heart’s electrical activity can be caused by a variety of medicines. Many medicines that are commonly used and well tolerated by many people are known to cause this effect in some people, and also if they are combined with any other such drugs.

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Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:October 3, 2018

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