Day traders are having fun with Palatin Technologies (PTN) - Get Report  following the penny drug stock's announcement that injections of its experimental drug bremelanotide increased the libido in women with low sex drive.

Palatin shares are up 71% to 83 cents per share in premarket trading Wednesday morning on the belief that the two bremelanotide phase III clinical trials achieved their primary efficacy endpoints. Palatin made the announcement Tuesday night after the markets closed.

Not so fast.

Palatin appears be to playing a game of bait and switch with the design of its phase III studies. What looks like a clean win for bremelanotide as a female libido enhancer might more honestly be described as a Palatin spin job aimed at masking the drug's disappointing inability to improve the frequency of sexual intercourse.

Here's how Palatin describes the primary endpoints of the dual phase III studies in Tuesday night's press release:

Based on discussions with the FDA, it was decided that the co-primary endpoints for the Phase 3 clinical trials were the Female Sexual Function Index: Desire Domain (FSFI-D) and Female Sexual Distress Scale-Desires/Arousal/Orgasm (FSDS-DAO) Item 13. Satisfying sexual events is a secondary endpoint.

Hmmm. That's not what Palatin has claimed in the past. lists "satisfying sexual events" and FSFI-D as co-primary endpoints of the bremelanotide phase III studies. FSDS-DAO is the secondary efficacy endpoint. Moreover, the co-primary endpoints are supposed to be measured after 32 weeks, not 24 weeks as claimed by Palatin on Tuesday night.

Palatin's most recent 10-K filing with the Securities and Exchange Commission describes the phase III studies this way:

The double blind or efficacy portion of each study consisted of a 24-week treatment evaluation period, with primary and key secondary endpoints of satisfying sexual events, or SSEs, the Female Sexual Function Index, or FSFI, desire subdomain (a 28 day recall), and question 13 of the Female Sexual Distress Scale-Desire/Arousal/Orgasm, or FSDS-DAO, questionnaire.

And here's the description of the studies in Palatin's 10-K filed for 2014:

A 24-week treatment evaluation period is being conducted, with co-primary endpoints of satisfying sexual events and the FSFI desire subdomain (a 28 day recall), and a key secondary endpoint utilizing question 13 of a revised FSDS questionnaire.

On Tuesday, Palatin emphasized the ability of bremelanotide to improve women's desire to have sex and decrease the distress associated with sex, but the company said nothing about increasing the frequency of sex, even though this was supposed to be at least one of two co-primary efficacy measures in the phase III studies.

By its own admission, Palatin acknowledged Tuesday the bremelanotide study results, while statistically significant, only just barely met the threshold for a clinically meaningful improvement in sexual desire and reduction in sexual distress.

When you add in the inability to increase the frequency at which women are engaging in satisfying sex and the requirement that women inject themselves 45 minutes before engaging in sex, bremelanotide's libido-boosting qualities look decidedly less hot.

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.