The occurrence of adverse drug reactions is common, owing to its narrow therapeutic index (the margin between effectiveness and toxicity). Gynaecomastia (enlargement of breast tissue) is mentioned in many textbooks as a side effect, thought to be due to the estrogen-like steroid moiety of the<unk>  molecule, but when systematically sought, the evidence for this is equivocal . The combination of increased (atrial) arrhythmogenesis and inhibited atrioventricular (AV) conduction (for example paroxysmal atrial tachycardia with AV block – so-called "PAT with block") is said to be pathognomonic (that is, diagnostic) of<unk>  toxicity.<unk>  can lead to cardiac arrhythmias when given with thiazides and loop diuretics. This is because co-administration of<unk>  with drugs such as thiazides and loop diuretics which can cause hypokalemia, low serum levels of potassium in the blood. This exacerbates the potential for cardiac arrythmias because the low levels of potassium reduces the amount of K+ at the ATPase pump and increase calcium levels too much which leads to these arrythmias. It can also cause visual disturbances as well as dizziness or fainting. Several other drugs associated with ADRs in concommitant use include verapamil, amiodarone, quinidine, tetracycline, and erythromycin.
Digoxin
Digitoxin
Amiodarone
Metoprolol
Carvedilol
Sotalol
Bisoprolol
Captopril