Q Will 5-HTP lower my sex drive because of serotonin's conflict with dopamine?

A The effects of serotonin on sex drive is directly related to the relative amount (as is the case with most compounds) and especially to the type of serotonergic receptors that are stimulated. In rat studies, stimulation of the 5-HT1 receptors increases sexual facilitation, and stimulation of 5-HT2 receptors produces sexual inhibition.1 In a particular study with male rats, 5-HTP produced an increased number of mounts and intromissions to ejaculation. When the lab animals were pretreated with benserazide, a carboxylase inhibitor that causes serotonin production to decrease peripherally and to increase in the brain, there was a further delay in the length of time to ejaculation. [This might be positive depending on the state of your libido.] The effect of 25 mg of 5-HTPdelivered intraperitoneally to female rats reduced lordosis, or sexual posturing. This is the equivalent of many times this amount given orally.

Rest assured that the amount of 5-HTP needed to reduce the sex drive is large, and that according to one study, the subthreshold was 12.5 mg/kg of body weight for rats. All other things equal, this would translate to about 850 mg of 5-HTP for a 150-lb. human.2Since "garden variety" deficiency-syndrome usage is 50 to 200 mg, sexual inhibition is unlikely to occur.


  1. Ahlenius S, Larsson K. Opposite effects of 5-methoxy-N,N-di-methyl-tryptamine and 5 hydroxytryptophan on male rat sexual behavior. Pharmacol Biochem Behav 1991;38:201-205.
  2. Fernandez-Guasti A, Rodriguez-Manzo G. Further evidence showing that the inhibitory action of serotonin on rat masculine Sexual behavior is mediated after the stimulation of 5-HT1B receptors. Pharmacol Biochem Behav 1992; 42:529-533.