They both are mixed oral contraceptive pills. Femodene ED contains estrogen and progesterone and Trigestrel contains Ethinyl estradiol and Levonornorgestrel. As they both are hormonal medications a possibility of gaining weight is present, but there's nothing to suggest that the medicine will induce this as it depends from one person's body to another so there isn't a definitive manner to say you can develop a side effect. If you do develop kindly visit your treating gynecologist and inform the changes so that the medications can be changed accordingly.