Macrolides fall into the class of anti-bacterial drugs. These are the most widely used antibacterial drugs. They show an activity against a very broad range of bacteria. Before we comment upon whether macrolides are responsible for QT elongation, let us first have a quick look at what they are and what their mechanism of action is.
Macrolides have been present in the medical market since quite a long time and since after their discovery, they have proven to be amazingly successful in treating a wide variety of bacterial infections.
Some of the most commonly prescribed macrolides are azithromycin, clarithromycin, erythromycin etc.
Though macrolides are widely used for the treatment of gram-positive bacteria, they also show their action on a limited range of gram-negative bacteria. Also, they are a relatively good option in those patients who have an allergy to penicillin. They also cover a few other organisms; which penicillin does not cover.
Macrolides are widely used for the treatment of respiratory tract infections, skin infections, soft tissue infections, pneumonia etc.
Macrolides do their work by acting as bacteriostatic agents. It means that they stop the growth of the bacteria, and thus they give our body a chance to fight over the bacterial infection. Erythromycin was the first macrolide to be introduced and is effective against a great variety of gram-positive organisms. Its action on gram-negative bacteria, though, is a bit limited.
Do Macrolides Cause QT Prolongation?
Macrolides may also be responsible for causing QT prolongation is some individuals. Macrolides are known to interact with statins, e.g., atorvastatin. This can result in very dangerous myopathy. Macrolides are also to be used very cautiously in patients taking other medications which may prolong QT interval, like quinolones, anti-psychotic drugs, etc.
Macrolides are otherwise a wonderful class of antibiotics. They are proven to be immensely successful in treatment of a number of bacterial infections. However, as with any medications, caution is very important here, especially when pairing macrolides with other potential QT prolonging drugs. Proper consultation is always recommended before taking any medications.
Let us now have a quick look at what a normal QT interval is and what is meant by a long QT syndrome.
Our heart follows a particular cycle, which is an electric cycle. Every time when the heart beats, with every heartbeat an electrical signal is sent from the top of the heart or the sinus node to its bottom. This results in contraction and relaxation of atriums and ventricles in the heart. This results in pumping of blood from the heart to the whole body. This whole phenomenon is very expertly and carefully orchestrated. The electrical conduction system of the heart causes the contraction of the heart muscles. It involves the depolarisation and repolarisation of the ventricles of the heart. These signals are responsible for the contraction of right and left atrium first and then the right and left ventricles. This process is responsible for the proper and regular pumping of the blood throughout the body. The hearts electrical activity is measured by an electrocardiogram, also known commonly as ECG. This depolarisation and repolarisation of ventricles is represented by the QT interval on an ECG. There are five electrical waves for every heartbeat-p, q, r, s and t. all this is recorded on a graph. Studying this graph can help a physician to gauge the hearts electrical activity and find any abnormalities in it. If this qt interval is prolonged, it may be a potential indicator of ventricular tachycardia. (Tachycardia is increased rate of the heartbeats in a resting phase of the body).
This QT interval can get prolonged due to a number of reasons. Some of them include congenital heart disease, or a history in the family of the same, renal failure, cardiac failure, other disturbances like diarrhea and vomiting, as there may be a loss of potassium, hypokalaemia, hypomagnesaemia, and some medicines even, like antipsychotic or antidepressants.
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