Repeated administration of mazindol reduces spontaneous pain-related behaviors without modifying bone density and microarchitecture in a mouse model of complete Freund's adjuvant-induced knee arthritis.

BACKGROUND: The role of dopaminergic system in the development of rheumatoid arthritis-related pain, a major symptom in this disease, has not been explored. Therefore, the anti-nociceptive effect of mazindol, a dopamine uptake inhibitor, was evaluated in a model of complete Freund's adjuvant (CFA)-induced arthritis. Furthermore, as studies have shown that the dopaminergic system regulates bone metabolism, the effect of mazindol on bone mass and microarchitecture was determined. METHODS: Adult ICR male mice received intra-articular injections of either CFA or saline into the right knee joint every week. Spontaneous pain-like behaviors (flinching and guarding) and locomotor activity were assessed at day 26 post-first CFA, following which, a single intraperitoneally (i.p.) administered dose of mazindol was given (1, 3 and 10 mg/kg). Then, the antinociceptive effect of a repeated administration of 3 mg/kg mazindol (daily, i.p.; day 15-day 26) was evaluated. Additionally, at day 26, the participation of D1-like, D2-like or opioid receptors in the antinociceptive effect of mazindol was evaluated. The effect of mazindol on bone density and microarchitecture was evaluated by micro-computed tomography. RESULTS: Acute administration of mazindol decreased the spontaneous pain-like behaviors in a dose-dependent manner without reducing the knee edema. However, mazindol at 10 mg/kg significantly increased the locomotor activity; therefore, 3 mg/kg mazindol was used for further studies. Repeated administration of 3 mg/kg mazindol significantly decreased the pain-like behaviors without modifying locomotor activity. The antinociceptive effect of mazindol was blocked by administration of a D2-like receptor antagonist (haloperidol), but not by administration of D1-like receptor antagonist (SCH 23390) or an opioid receptor antagonist (naloxone). Repeated administration of mazindol did not significantly modify the density and microarchitecture of periarticular bone of the arthritic and nonarthritic knee joints. CONCLUSION: Results suggest that mazindol via D2-like receptors has an antinociceptive role in mice with CFA-induced knee arthritis without modifying the bone health negatively.

Antiallodynic Activity of Ceftriaxone and Clavulanic Acid in Acute Administration is Associated with Serum TNF-α Modulation and Activation of Dopaminergic and Opioidergic Systems.

Preclinical Research The aim of this study was to determine the antiallodynic effect of acute administration of the ß-lactam antimicrobials, ceftriaxone (CFX) and clavulanic acid (CLAV), for the control of established pain on a model of neuropathic pain (NP). We also investigated the involvement of dopaminergic and opioidergic pathways as well as alterations in serum concentrations of TNF-α in the antiallodynic actions of these drugs. CFX, CLAV, or gabapentin (GAP), a reference drug, were administered i.p. twelve days after constriction of the sciatic nerve in rats. Mechanic and cold allodynia were evaluated for 3 h and alterations in serum concentration of TNF-α determined. Both CFX and CLAV had antiallodynic effects in response to mechanical and cold stimulation, similar to GAP. The antiallodynic effects of CFX and CLAV were blocked by haloperidol (HAL), a D2 receptor antagonist, and by naloxone (NLX), an opioid receptor antagonist. Additionally, serum TNF-α levels were attenuated following CFX and CLAV administration. These results suggest that acute administration of CFX and CLAV may represent a promising approach for treating the acute allodynia of NP, and that the mechanisms involved in these effects involve activation of dopaminergic and opioidergic pathways as well as modulation of TNF-α production. Drug Dev Res 78 : 105-115, 2017. © 2017 Wiley Periodicals, Inc.

A prospective, open-label, multicentre study of pregabalin in the treatment of neuropathic pain in Latin America.

AIMS: The objective of this study was to evaluate the safety and efficacy of pregabalin at flexible doses of 150-600 mg/day in Latin American patients with neuropathic pain. METHODS: A prospective, multicentre, open-label, non-comparative study included patients age >or= 18 years diagnosed with neuropathic pain associated with diabetic peripheral neuropathy, postherpetic neuralgia, chemotherapy-induced peripheral neuropathic pain (PNP), or human immunodeficiency virus-related PNP. Eligible patients (N = 121) had a score of >or= 40 mm on the visual analogue scale and a daily pain rating scale (DPRS) score of >or= 4 throughout screening. Patients received flexible-dose pregabalin (150-600 mg/day) for 12 weeks, which included a 4-week dose-adjustment phase. The primary efficacy measure was change from baseline to end of treatment/last observation carried forward (EOT/LOCF) in weekly mean pain score on the DPRS. Secondary efficacy measures included pain, anxiety, sleep interference, treatment satisfaction and Patient and Clinician Global Impression of Change. RESULTS: Pregabalin significantly reduced the weekly mean pain score on DPRS from baseline to EOT/LOCF [-3.8 (95% CI: -4.2 to -3.3); p < 0.0001]. Reductions from baseline to EOT/LOCF were observed for all secondary efficacy outcomes (p < 0.0001). Pain and sleep interference were significantly improved compared with baseline across all weeks of the study, as early as 1 week after initiation of pregabalin (p < 0.0001). The most common adverse events (AEs) were somnolence, dizziness, weight gain and peripheral oedema. Nine (7.4%) patients discontinued the study because of AEs and 25 (20.7%) temporarily stopped or reduced their pregabalin dose because of AEs. CONCLUSIONS: Flexible-dose pregabalin (150-600 mg/day) significantly reduced pain and anxiety and improved sleep and was generally well tolerated in Latin American patients with neuropathic pain.