Cat's claw

Cat's claw is an over-the-counter herbal extract. The double-blind RCT by Mur (J Rheumatol 2002) in 40 patients with rheumatoid arthritis on stable sulfasalazine or hydroxychloroquine: a pentacyclic oxindole Uncaria tomentosa extract (Saventaro 60 mg/day for 24 weeks) reduced the tender joint count by a mean 53% versus 24% in the placebo group. Study quality is moderate, sample size small and the effect has not been reproduced in large RCTs. A small RCT by Piscoya (Inflamm Res 2001) in knee osteoarthritis showed moderate pain reduction with Uncaria guianensis (a related species) 100 mg/day for 4 weeks. EULAR 2022 and SER 2019 recommend methotrexate as first line in rheumatoid arthritis and, when needed, biological or targeted synthetic DMARDs (adalimumab, tofacitinib). Cat's claw is not mentioned in international or Spanish rheumatology guidelines and is considered an add-on, not a replacement for DMARDs. If cat's claw is considered instead of prescribed methotrexate, discuss with a rheumatologist – untreated rheumatoid arthritis progresses with joint destruction within the first or second year.

Cat's claw is marketed as a «natural cure for chronic Lyme disease», «cancer treatment without chemotherapy» and «HIV remedy». There is no evidence base for these claims. FTC in 2000, as part of Operation Cure.all, brought legal action against cat's claw manufacturers over cancer and HIV cure claims – the cases were settled in 2000-2001 with bans on such claims. NCCIH (NIH) and IDSA 2020 are unambiguous: in serology-confirmed Lyme disease, standard treatment is doxycycline or amoxicillin for 10-21 days in early disease and up to 28 days in late disease; «chronic Lyme disease» (PTLDS) is a contested diagnosis, and prolonged antibiotic therapy did not work in the STOP-LD and Klempner RCTs, let alone cat's claw. In oncology and HIV, cat's claw does not replace chemotherapy, immunotherapy or antiretroviral therapy – treatment delay reduces survival. If cat's claw was bought instead of prescribed antibiotic therapy, chemotherapy or ART, discuss with a doctor – in these diagnoses, delay of standard treatment costs years of life.