Is it normal for Spironolactone to affect your monthly cycle?

Spironolactone and trinessa do not have any specific interactions with each other.  However, spironolactone can cause menstrual irregularities. Triphasic birth control pills such as your trinessa can also sometimes cause menstrual irregularities on their own, altho it sounds like your issue only started when the spironolactone was added.  Sometimes in our practice, we switch the patient to a monophasic birth control pill such as loestrin and this works to stop the menstrual irregularities with the spironolactone.  In our practice, we tend to use the 100mg dose of spironolactone instead of the 50 mg and we have not seen much incidence of the period issues.  If neither one of these suggestions work and the menstrual irregularity becomes too much of an issue, you may have to stop the spironolactone.