Guaco, Or Huaco a name given in the tropical regions of America to several plants used as antidotes for the bites of poisonous snakes. Aristolochia guaco is said to be the one most in repute; and so great is the confidence in its efficacy that the Indians and negroes of parts of South America will not undertake a journey without carrying some of the dried leaves of the plant. The aristolochias are generally climbing plants, with grotesquely formed and often lurid-colored flowers. Two North American species of aristolochia were found by the early settlers to be in use among the aborigines for the same purposes as the South American one, and they still retain the name of Virginia snakeroot. The name guaco is also given to one of the composite family, the mikania guaco, described by Humboldt and Bonpland as a plant with twining stems, leaves ovate, pointed, and dentate, and flowers in opposite, axillary corymbs. The fresh leaves are bruised and applied to the wound, and they are also made to yield an infusion which is drunk at the same time.

The preparation has a bitter, disagreeable taste, and acts as a mild tonic and a gentle stimulant to the secretions.