The Effectiveness and Safety of Pharmaceutical-Grade Cannabidiol in the Treatment of Mastocytosis-Associated Pain: A Pilot Study.

Mastocytosis patients often experience a number of symptoms, including mastocytosis-associated pain that is difficult to manage due to resistance to usual antalgic treatments and/or the patient's poor tolerance. Mastocytosis patients display significantly higher levels of indoleamine-2,3-dioxygenase-1 (IDO1) activity, leading to hyperactivation of the N-methyl-D-aspartate receptor. As cannabidiol (CBD) is known to inhibit IDO1's enzymatic activity, we hypothesized that pharmaceutical-grade CBD is an effective treatment for mastocytosis-associated pain. Patients with non-advanced mastocytosis and refractory pain were eligible for inclusion in this observational pilot study. CBD was initiated at 50 mg/day and increased to a maximum of 900 mg/day. Pain was scored on a 0-to-10 numerical rating scale (NRS). A total of 44 patients were included over a 2-year period. The median dose of CBD prescribed was 300 mg/day (range: 50-900 mg/day). Elevated liver enzymes were observed in one patient. The mean ± standard deviation NRS pain score decreased significantly from 7.27 ± 1.35 before treatment to 3.78 ± 1.99 after 3 months of treatment (p < 0.0001). Fifteen patients (34%) were able to discontinue all their previous antalgic medications. CBD treatment might be a safe, effective treatment for mastocytosis-associated pain and its use requires confirmation in a randomized, controlled trial.

Analgesic Effects of Topical Amitriptyline in Patients With Chemotherapy-Induced Peripheral Neuropathy: Mechanistic Insights From Studies in Mice.

Oral amitriptyline hydrochloride (amitriptyline) is ineffective against some forms of chronic pain and is often associated with dose-limiting adverse events. We evaluated the potential effectiveness of high-dose topical amitriptyline in a preliminary case series of chemotherapy-induced peripheral neuropathy patients and investigated whether local or systemic adverse events associated with the use of amitriptyline were present in these patients. We also investigated the mechanism of action of topically administered amitriptyline in mice. Our case series suggested that topical 10% amitriptyline treatment was associated with pain relief in chemotherapy-induced peripheral neuropathy patients, without the side effects associated with systemic absorption. Topical amitriptyline significantly increased mechanical withdrawal thresholds when applied to the hind paw of mice, and inhibited the firing responses of C-, Aß- and Aδ-type peripheral nerve fibers in ex vivo skin-saphenous nerve preparations. Whole-cell patch-clamp recordings on cultured sensory neurons revealed that amitriptyline was a potent inhibitor of the main voltage-gated sodium channels (Nav1.7, Nav1.8, and Nav1.9) found in nociceptors. Calcium imaging showed that amitriptyline activated the transient receptor potential cation channel, TRPA1. Our case series indicated that high-dose 10% topical amitriptyline could alleviate neuropathic pain without adverse local or systemic effects. This analgesic action appeared to be mediated through local inhibition of voltage-gated sodium channels. PERSPECTIVE: Our preliminary case series suggested that topical amitriptyline could provide effective pain relief for chemotherapy-induced peripheral neuropathy patients without any systemic or local adverse events. Investigation of the mechanism of this analgesic action in mice revealed that this activity was mediated through local inhibition of nociceptor Nav channels.

High concentration of topical amitriptyline for treating chemotherapy-induced neuropathies.

PURPOSE: Chemotherapy-induced peripheral neuropathy (CIPN) is a devastating pain condition of cancer therapy that may force chemotherapy dose reduction or discontinuation. Since treatment options for CIPN are quite limited, we investigated the effect of 10% amitriptyline cream on neuropathic pain. PATIENTS AND METHODS: This pilot study enrolled patients with hematological or solid tumors presenting hands and feet CIPN (for less than 1 month without previous treatment for CIPN [Group 1]; for more than 1 month with previous treatment [Group 2]). Patients applied 10% amitriptyline cream twice a day. Pain intensity was evaluated at 1, 2, and 4 weeks then monthly up to 1 year. The primary endpoint was change from baseline to 4-week treatment in median pain score assessed by visual analogue scale (VAS). RESULTS: Overall, 44 patients were enrolled. Median (range) age was 67 (46-80) years, 34% were female. The majority (88.6%) had hematological malignancies, and the most commonly used chemotherapeutic agents were bortezomib and oxaliplatin. The median (range) VAS pain score decreased from 7 (4-9) at baseline to 2 (0-4) after 4-week topical treatment. No difference was seen between Group 1 and Group 2. Reduced initial chemotherapy doses in 11 patients as well as chemotherapy discontinued in 5 patients at baseline were resumed after treatment with 10% amitriptyline cream. CONCLUSION: Considering the limited efficacy of conventional systemic treatments in CIPN and their safety profile, 10% topical amitriptyline appears to be a good candidate for first-line CIPN therapy, allowing continuation of chemotherapy at effective doses. The results are worth to be confirmed in a placebo-controlled clinical trial.