J Altern Complement Med. 2001 Apr; 7(2): 175-85.

The safety of low-dose Larrea tridentata (DC) Coville (creosote bush or chaparral): a retrospective clinical study.

Heron S, Yarnell E.

Naturopathic Family Health Care, Sedona, AZ, USA.

OBJECTIVE: To determine whether internal use of low doses of Larrea tridentata tincture or topical applications of this traditional herbal medicine are safe. DESIGN: Retrospective review of all people prescribed Larrea for internal or for topical use over a 22-month period. SETTING/LOCATION: A general naturopathic practice in Sedona, Arizona. SUBJECTS: Thirteen patients were identified for whom Larrea tincture for internal use was prescribed. An additional 20 female and 3 male patients were identified for whom an extract of Larrea in Ricinus communis (castor) oil for topical use was prescribed. No patient had any history of liver disease. INTERVENTIONS: Larrea was prescribed as part of the usual care of each patient. In all cases it was given as either part of a complex herbal formula individualized for each patient containing less than 10% Larrea tincture or as an extract in Ricinus oil for topical use. OUTCOME MEASURES: Serum liver enzyme levels as well as blood urea nitrogen and creatinine levels, glucose levels, electrolytes, bilirubin levels, iron levels, ferritin levels, lipid levels, and complete blood count (CBC) were available for analysis in four patients; general clinical history and physical examination findings were relied on in all other cases. RESULTS: The four patients with complete before and after blood chemistry panels and CBC had no indication of liver damage from use of Larrea. This included one patient who was taking medications with significant potential for hepatotoxicity. No patient in the study, whether using Larrea for short term or long, internally or externally, showed any sign of organ damage during the period of follow-up. CONCLUSIONS: Relatively small intakes of Larrea tincture, or topical application of extracts in Ricinus oil, are safe when prescribed by a clinically trained botanical prescriber. Larrea should be used with caution in persons with a history of previous, or current, liver disease. It may be preferable to avoid the use of Larrea capsules because they have been associated with potentially dangerous overdosing.