Does Gardiomac tablet or spray reduce the effectiveness of Microgynon 21?

Since there is no such product as "gardiomac", I suppose that perhaps you are referring to Gardimax Medica - a throat spray or lozenges containing chlorhexidine and lidocaine. There is no information that these substances react negatively with hormonal contraception such as Microgynon 21. However, it is worth keeping an interval for the reason that for some time after sucking a tablet or aerosol application, you should not drink or eat - the anesthetic effect of lidocaine can reduce the sensitivity to the heat of meals and be the cause of burns. In addition, a feeling of anesthesia or numbness in the mouth and throat, although helpful in connection with pain, can cause difficulty in swallowing. I enclose information that may be helpful: https://www.gdziepolek.pl/produkty/31921/gardimax-medica-spray-aerozol/apteki https://www.gdziepolek.pl/produkty/31920/gardimax-medica-tabletki-do-ssania-gryzienia-zucia/apteki