Mass production has rendered this once-rare serum easy and inexpensive to obtain. Upon drinking this elixir, your biology instantly transforms to take on a set of sexual characteristics of your choice, changing both your appearance and physiology accordingly. You have some mild control over the details of this change, but you retain a strong “family resemblance” to your former appearance.
The elixir’s magic functions instantaneously and cannot be dispelled. Your new anatomy is as healthy and functional as your previous body’s, potentially allowing you to conceive, carry, or bear children (depending on your species’ biology). Drinking a second elixir of sex shift either reverts you back to a former form or allows you to adopt other sexual characteristics, as you choose. The elixir has no effect if you are unwilling, and the presence of certain sex-specific biological processes, such as gestation, may prevent this serum from taking effect.