Natural Medicines Newsletter

Volume 1, Issue 40, 10/22/2009

Question

Why should the herbal or natural medicine Cat's Claw not be taken during pregnancy?

Answer

Cat's claw (Uncaria tomentosa) is a plant found in the Amazon River basin.(1)  It gets its name from the curved, hooked thorns present on the vine which resemble a cat's claw.(1)  It has been used for centuries in South America for conditions such as chronic inflammatory disorders, viral infections, arthritis, gastrointestinal illnesses, cancer and even as birth control.(1-4)   As it relates to contraception, the safety and efficacy of Cat's claw is limited, but there are reports that if consumed in large amounts (dose not known) at the time of menstruation it can potentially cause sterility for 3 to 4 years with one dose.(5)  Despite this claim about its use, it is not recommended for use during pregnancy. 

What is the mechanism of action of Cat's claw in relation to its use as a contraceptive and reason to avoid during pregnancy?
There are several proposed mechanisms that are linked to its use for the above indications, but as it relates to contraception and use in pregnancy, it is likely the...