Make them more suggestible.

"The first three orgasms during a refractory period causes the mind to loose any trains of thought. After the fourth, they cannot think about anything other than sex and pleasure. With each orgasm they also become more passive and submissive, until the seventh, when they become incredibly suggestible. Effects of suggestions can carry over after they leave this state, and work best when reinforced with orgasms. More complicated or unusual suggestions may require more repetition or orgasms. However, even if a command cannot manifest normally, it will take control with the first orgasm in the refractory period, replacing the normal effects, although after seven they will still become suggestible. It is difficult to remember what happened during the refractory period, like when you are very drunk."