Editing Digoxin (section)

== Side effects ==
{{Main|List of side effects of digoxin}}
{{See|Digoxin toxicity}}
The occurrence of [[adverse drug reaction]]s 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 (chemistry)|moiety]] of the digoxin molecule,<ref name=Moscovitz>{{cite journal | vauthors = Moscovitz T, Aldrighi JM, Abrahanshon PA, Zorn TM, Logullo AF, Gebara OC, Rosano GG, Ramires JF | display-authors = 6 | title = Repercussions of digoxin, digitoxin and estradiol on the endometrial histomorphometry of oophorectomized mice | journal = Gynecological Endocrinology | volume = 20 | issue = 4 | pages = 213–20 | date = April 2005 | pmid = 16019364 | doi = 10.1080/09513590400021219 | s2cid = 22855158 }}</ref> but when systematically sought, the evidence for this is equivocal {{as of|2005|lc=1}}.<ref name=Ptherapy1993>{{cite journal | vauthors = Thompson DF, Carter JR | title = Drug-induced gynecomastia | journal = Pharmacotherapy | volume = 13 | issue = 1 | pages = 37–45 | year = 1993 | pmid = 8094898 | doi = 10.1002/j.1875-9114.1993.tb02688.x | s2cid = 30322620 }}</ref> The combination of increased ([[atrial]]) [[arrhythmia|arrhythmogenesis]] and inhibited [[atrioventricular node|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 digoxin toxicity.<ref name=Doering1977>{{cite journal | vauthors = Doering W, König E, Sturm W | title = [Digitalis intoxication: specifity and significance of cardiac and extracardiac symptoms. part I: Patients with digitalis-induced arrhythmias (author's transl)] | language = de | journal = Zeitschrift für Kardiologie | volume = 66 | issue = 3 | pages = 121–8 | date = March 1977 | pmid = 857452 | trans-title = ''Digitalis'' intoxication: specificity and significance of cardiac and extracardiac symptoms. Part I: Patients with ''[[Digitalis]]''-induced [[Heart arrhythmia|arrhythmia]]s }}</ref>

Digoxin can lead to cardiac arrhythmias when given with thiazides and loop diuretics. This is because co-administration of digoxin 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 arrhythmias 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 arrhythmias.<ref>{{cite book | vauthors = Ritter J, Lewis L, Mant T, Ferro A |title=A Textbook of Clinical Pharmacology and Therapeutics |date=2008 |publisher=Hodder Arnold |location=London |isbn=978-0-340-90046-8 |page=75 |edition=5th}}</ref>  It can also cause visual disturbances as well as dizziness or fainting.

Several other drugs associated with adverse drug reactions in concomitant use include [[verapamil]], [[amiodarone]], [[quinidine]], [[tetracycline]], and [[erythromycin]].