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.
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 alkaloids present in Cat's claw. The
number of alkaloids are extensive, but some have been identified as being
isopteropodine, isorhynchophylline, isomitraphylline, isocorynoxeine,
mitaphylline, pteropodine, rhynchophyline, and speciophylline.1,5 It
is alkaloids such as these in Cat's claw that have been shown to have
antiproliferative effects in breast cancer cells, leukemic and lymphoma cell
lines.6,7 It appears that the antiproliferative effects are not cytogenic
or mutagenic, but rather are through an induction of apoptosis (programmed cell
death).7-9 It is likely for this reason that Cat's claw has been used as
a treatment for cancer - where apoptosis is largely inhibited.1,5
could Cat's claw be used as a contraceptive, but not used during pregnancy?
While we are not aware of any definitive data, it is
plausible that the contraceptive effects of Cat's claw are related to its
antiproliferative effects and induction of apoptosis. It is important to
note that this effect has been studied in the context of cancer, not
contraception. Nevertheless, given this known mechanism, it is conceivable
that while conception may still be taking place, the fetus may be aborted due
to the failure of cellular replication and/or differentiation. This would
be especially true if exposure to Cat's claw were to occur during the first 8
to 9 weeks of gestation. In addition, it is possible that Cat's claw
could affect follicle development to the point that ovulation does not result
in the release of a viable oocyte. A review of the literature did not
provide any documented mechanisms for either of the above. However, other
plant alkaloid based chemotherapeutic agents (such as paclitaxel and
vincristine) are known to be pregnancy category D due to fetal malformations
noted in animal studies.
due to the known constituents present in Cat's claw, their known
antiproliferative effects on various cancer cell lines, other plant alkaloid
based chemotherapeutic agents known to cause fetal malformations in animal
studies and the lack of safety or efficacy studies for these situations, it is
advisable that females of child-bearing age who are sexually active or pregnant
women should avoid the use of Cat's claw regardless of its desired use.
- Valerio LG Jr, Gonzales GF. Toxicological aspects of the South
American herb's cat's claw (Uncaria tomentosa) and Maca (Lepidium
meyenil): a critical synopsis. Toxicol Rev 2005;24:11-35.
JE. Review of antiviral and immunomodulating properties of plants of
the Peruvian rainforest with a particular emphasis on Una de Gato and
Sangre de Grado. Altern Med Rev 2001;6:567-79.
J, Rodriguez Z, Bustamante SA et al. Efficacy and safety of
freeze-dried cat's claw in osteoarthritis of the knee: mechanism of
action of the species Uncaria guyanensis. Inflamm Res 2001;50:442-8.
E, Hartig F, Eibl G et al. Randomized double blind trial of an extract
from the pentacyclic alkaloid-chemotype of Uncaria tomentosa for the
treatment of rheumatoid arthritis. J Rheumatol 2002;29:678-81.
- Physicians' Desk Reference for Herbal Medicines. 4th edition. Cat's Claw. Thompson Healthcare Inc. 2007:168-70.
L, Coradini D, Di Fronzo G et al. The antiproliferative effects of
Uncaria tomentosa extracts and fractions on the growth of breast cancer
cell line. Anticancer Res 2001;21:2457-61.
Y, Pero RW, Amiri A et al. Induction of apoptosis and inhibition of
proliferation in human tumor cells treated with extracts of Uncaria
tomentosa. Anticancer Res 1998;18:3363-8.
Maria A, Lopez A, Diaz MM et al. Evaluation of the toxicity of Uncaria
tomentosa by bioassays in vitro. J Ethnopharamacol 1997;57:183-7.
R, Re F, Bianchi A et al. Mutagenic and antimutagenic activities of
Uncaria tomentosa and its extracts. J Ethnopharmacol 1993;38:63-77.