What the Research Says
I found only one study on Medline regarding catuaba. Back in 1992, researchers in Japan found catuaba extracts to have potential antibacterial and anti-HIV activity in mice. Human trials are not available.

Mechanism of Action
The constituents found in catuaba include alkaloids (catuabine A, B, and C), tannins, aromatic oils and fatty resins, phytosterols, and cyclolignans. How catuaba works is not known.

My Experience
I took 1 ml of catuaba tincture morning and lunch for three days. I noticed that my erections were easier to start and maintain, but I didn't experience any other physical or mental effects.

Side Effects
There are no known side effects, however the use of catuaba in North America is relatively new.

Dosage and Availability
Catuaba is usually consumed as a tea made from the bark. Natives claim that after drinking one to three cups of tea steadily over a period of a few days or weeks, the first effects that occur are usually erotic dreams, and then increased sexual desire. Claims have been made that an alcohol tincture extract contains more of the active constituents and provides better results, although I have not come across research to document this. Capsules are sold containing a range of 500 to 1,000 mg. The dose would be 1 to 2 g per day. One full dropper of the tincture can be taken twice a day with breakfast and lunch.

Summary
Catuaba has been used traditionally in combination with muira puama. Muira puama has a stronger effect on energy, mood, and overall sexual interest, and it would seem logical to combine it with catuaba, which, to me, had a more direct effect on the genital region.

Catuaba can certainly be combined with other herbs and nutrients, including tongkat ali, yohimbe, tribulus, and others.