Spironolactone has been studied at extremely high oral doses of up to 2,400 mg per day in clinical trials. Its oral median lethal dose (LD50) is more than 1,000 mg/kg in mice, rats, and rabbits.There is no specific antidote for overdose of spironolactone. Treatment may consist of induction of vomiting or stomach evacuation by gastric lavage. The treatment of spironolactone overdose is supportive, with the purpose of maintaining hydration, electrolyte balance, and vital functions. Spironolactone should be discontinued in people with impaired kidney function or hyperkalemia. Interactions
Spironolactone often increases serum potassium levels and can cause hyperkalemia, a very serious condition. Therefore, it is recommended that people using this medication avoid potassium supplements and salt substitutes containing potassium. Physicians must be careful to monitor potassium levels in both males and females who are taking spironolactone as a diuretic, especially during the first twelve months of use and whenever the dosage is increased. Doctors may also recommend that some patients may be advised to limit dietary consumption of potassium-rich foods. However, recent data suggests that both potassium monitoring and dietary restriction of potassium intake is unnecessary in healthy young women taking spironolactone for acne. Spironolactone together with trimethoprim/sulfamethoxazole increases the likelihood of hyperkalemia, especially in the elderly. The trimethoprim portion acts to prevent potassium excretion in the distal tubule of the nephron.Spironolactone has been reported to induce the enzymes CYP3A4 and certain UDP-glucuronosyltransferases (UGTs), which can result in interactions with various medications. However, it has also been reported that metabolites of spironolactone irreversibly inhibit CYP3A4.
Current recommendations from the American Heart Association are to use spironolactone in patients with NYHA Class II-IV heart failure who have a left ventricular ejection fraction of less than 35%.In a randomized evaluation which studied people with severe congestive heart failure, people treated with spironolactone were found to have a relative risk of death of 0.70 or an overall 30% relative risk reduction compared to the placebo group, indicating a significant death and morbidity benefit of the medication. People in the studys intervention arm also had fewer symptoms of heart failure and were hospitalized less frequently. Likewise, it has shown benefit for and is recommended in patients who recently had a heart attack and have an ejection fraction less than 40%, who develop symptoms consistent with heart failure, or have a history of diabetes mellitus. Spironolactone should be considered a good add-on agent, particularly in those patients "not" yet optimized on ACE inhibitors and beta-blockers. Of note, a recent randomized, double-blinded study of spironolactone in patients with symptomatic heart failure with "preserved" ejection fraction (i.e. >45%) found no reduction in death from cardiovascular events, aborted cardiac arrest, or hospitalizations when spironolactone was compared to placebo.It is recommended that alternatives to spironolactone be considered if serum creatinine is greater than 2.5 mg/dL (221 μmol/L) in males or greater than 2 mg/dL (176.8 μmol/L) in females, if glomerular filtration rate is below 30 mL/min or with a serum potassium of greater than 5.0 mEq/L given the potential for adverse events detailed elsewhere in this article.