Among 31 human newborns exposed to spironolactone in the first trimester, there were no signs of any specific birth defects. A case report described a woman who was prescribed spironolactone during pregnancy with triplets and delivered all three (one boy and two girls) healthy; there was no feminization in the boy. In addition, spironolactone has been used at high doses to treat pregnant women with Bartters syndrome, and none of the infants (three boys, two girls) showed toxicity, including feminization in the male infants. There are similar findings, albeit also limited, for another antiandrogen, cyproterone acetate (prominent genital defects in male rats, but no human abnormalities (including feminization of male fetuses) at both a low dose of 2 mg/day or high doses of 50 to 100 mg/day). In any case, spironolactone is nonetheless not recommended during pregnancy due to theoretical concerns relating to feminization of males and also to potential alteration of fetal potassium levels.A 2019 systematic review found insufficient evidence that spironolactone causes birth defects in humans. However, there was also insufficient evidence to be certain that it does not. Overdose
Spironolactone is relatively safe in acute overdose. Symptoms following an acute overdose of spironolactone may include drowsiness, confusion, maculopapular or erythematous rash, nausea, vomiting, dizziness, and diarrhea. In rare cases, hyponatremia, hyperkalemia, or hepatic coma may occur in individuals with severe liver disease. However, these adverse reactions are unlikely in the event of an acute overdose. Hyperkalemia can occur following an overdose of spironolactone, and this is especially so in people with decreased kidney function.
Other general side effects include dehydration, hyponatremia (low sodium levels), mild hypotension (low blood pressure), ataxia (muscle incoordination), drowsiness, dizziness, dry skin, and rashes. Because of its antiandrogenic activity, spironolactone can, in men, cause breast tenderness, gynecomastia (breast development), feminization in general, and demasculinization, as well as sexual dysfunction including loss of libido and erectile dysfunction, although these side effects are usually confined to high doses of spironolactone. At very high doses (400 mg/day), spironolactone has also been associated with testicular atrophy and reversibly reduced fertility, including semen abnormalities such as decreased sperm count and motility in men. However, such doses of spironolactone are rarely used clinically. In women, spironolactone can cause menstrual irregularities, breast tenderness, and breast enlargement. Aside from these adverse effects, the side effects of spironolactone in women taking high doses are minimal, and it is well tolerated.The most important potential side effect of spironolactone is hyperkalemia (high potassium levels), which, in severe cases, can be life-threatening. Hyperkalemia in these people can present as a normal anion-gap metabolic acidosis. It has been reported that the addition of spironolactone to loop diuretics in patients with heart failure was associated with a higher risk of hyperkalemia and acute kidney injury (AKI). Spironolactone may put people at a heightened risk for gastrointestinal issues like nausea, vomiting, diarrhea, cramping, and gastritis. In addition, there has been some evidence suggesting an association between use of the medication and bleeding from the stomach and duodenum, though a causal relationship between the two has not been established.