PT-141 vs Viagra for Women: Desire vs Blood Flow

Why "Viagra for women" is the wrong comparison

Sexual response has several parts that can go wrong separately: desire (wanting sex), arousal (both feeling turned on and the physical changes, like swelling and lubrication), orgasm, and sometimes pain. Viagra was built for one physical step in men: getting enough blood flow for an erection. Low desire in women usually isn't a plumbing problem, which is why simply giving women Viagra didn't turn out to be the answer.

That doesn't mean blood flow never matters. Some women have plenty of desire but find their body doesn't respond, or that orgasm has become hard to reach, for example on certain antidepressants. The useful question isn't "which drug is stronger?" but "which part of my sexual response is the problem?" Our overview of female sexual dysfunction walks through these types.

How PT-141 works

PT-141 (bremelanotide) is a peptide that activates melanocortin receptors in the brain, mainly MC4, in areas that help drive sexual motivation. It targets desire rather than genital blood flow. As the Vyleesi injection, it is FDA-approved for premenopausal women with acquired, generalized hypoactive sexual desire disorder (HSDD).

In two 24-week trials of 1,267 premenopausal women, bremelanotide modestly improved desire scores and reduced distress compared with placebo, though it didn't significantly increase the number of satisfying sexual events (Kingsberg 2019). It is injected at least 45 minutes before sex, no more than once a day and no more than 8 times a month (Vyleesi label). For the full picture, see PT-141 for women.

How Viagra and Cialis work

Sildenafil (Viagra) and tadalafil (Cialis) are PDE5 inhibitors. They block an enzyme that breaks down cGMP, a molecule that relaxes smooth muscle in blood vessel walls. The result is more blood flow to genital tissue when someone is sexually stimulated. They don't create desire on their own; they amplify a physical response that has already started.

The main practical difference between the two is how long they last. Tadalafil has a half-life of about 17.5 hours, so its effect window is much longer than sildenafil's (Cialis label). Neither drug is FDA-approved for any sexual problem in women.

Does Viagra work for women? What the research shows

The evidence is mixed, and it depends a lot on who was studied.

• Broad arousal problems: no benefit. In a large trial of 781 women with female sexual arousal disorder (577 with normal estrogen levels and 204 with low estrogen), sildenafil was no better than placebo on any measure of sexual response (Basson 2002).
• Genital arousal problems after menopause: only a narrow subgroup. In a small crossover study of 34 postmenopausal women on estrogen who still felt mentally aroused but had lost genital response and orgasm, sildenafil didn't help the group overall. Only women with measurably low genital blood flow in lab testing seemed to benefit (Basson 2003).
• Antidepressant-related sexual problems: some benefit. In a randomized trial of 98 premenopausal women whose depression was in remission on SSRI-type antidepressants but who had sexual side effects, sildenafil taken before sex reduced those side effects compared with placebo. Headache, flushing and indigestion were common (Nurnberg 2008).

By the numbers

Sildenafil in women: what trials found

781women with arousal disorder: sildenafil no better than placeboSource: Basson 2002

98women on SSRIs: sildenafil reduced sexual side effects vs. placeboSource: Nurnberg 2008

PT-141 vs Viagra and Cialis: side by side

Safety: what you must know

PT-141

Nausea affected 40% of women in the trials, mostly after the first dose. Bremelanotide also causes a temporary rise in blood pressure after each dose (up to about 6/3 mmHg, usually gone within 12 hours) and is contraindicated with uncontrolled high blood pressure or known cardiovascular disease. About 1% developed darker skin patches that may not fully fade.

Sildenafil and tadalafil

Why midlife changes the question

For women in their 40s and 50s, several things often happen at once. Falling estrogen can thin and dry vaginal tissue and reduce blood flow and sensation. Sleep gets worse, mood can shift, and many women start or are already on antidepressants, blood pressure medicines or other drugs that affect sexual response. Long relationships, caregiving and work stress add their own weight.

That mix means a single pill rarely solves everything. A clinician will usually ask when the change started, whether it is desire, arousal, orgasm or pain (or several), what medicines you take, and whether you're still having periods. The answers point toward very different options:

• Vaginal dryness or pain often responds to lubricants, moisturizers or low-dose vaginal estrogen.
• Antidepressant-related problems may be helped by adjusting the antidepressant (only with your prescriber) or by adding a PDE5 inhibitor.
• Persistent, distressing low desire may warrant a desire-focused medicine or, after menopause, testosterone.
• Stress, body image and relationship issues respond best to sex therapy or counseling, alone or alongside medicine.

Our guide to low libido during menopause covers the hormonal side in more detail.

When might a combination make sense?

Because desire and arousal are different problems, some clinicians consider combining a desire-focused medicine with a blood-flow one. There are no large trials of PT-141 plus a PDE5 inhibitor in women, so any combination is off-label and should only be prescribed after a full health and medication review.

Amie offers one such compounded combination: Blys™, a rapid-dissolve tablet with PT-141, oxytocin and tadalafil, taken 30 to 60 minutes before intimacy for low desire and arousal. It was designed with women taking antidepressants in mind. Blys is not FDA-approved, and a licensed clinician decides whether it is appropriate for you. Because it contains tadalafil, it must never be used with nitrates, and anyone with heart disease, low or uncontrolled blood pressure, or who takes blood pressure medicines needs careful review first.

How to decide what to ask about

• If you rarely want sex and that bothers you, desire-focused options such as flibanserin (approved for women under 65) or bremelanotide (approved before menopause) are the FDA-approved choices; see PT-141 vs Addyi.
• If you want sex but your body doesn't respond, or orgasm has become hard on an antidepressant, a PDE5 inhibitor may be worth discussing.
• If sex hurts or you're dry after menopause, treating the vaginal tissue usually comes first; neither PT-141 nor Viagra fixes that.
• If you're postmenopausal with low desire, testosterone has the strongest evidence; see testosterone and libido in women.