Methylphenidate and Morphine Combination Therapy in a Rat Model of Chronic Pain

The Effect of Antinociceptive Dose of Morphine on Cell Therapy in Rats with Spinal Cord Injury

Spinal cord injury (SCI) is a sensory-motor injury. Today, combined treatments such as cell therapy along with drug therapy and their interactions are of interest. Morphine is an opioid drug used to relieve intolerable pain. This study aims to evaluate the impact of an antinociceptive dose of morphine (with minimal tolerance/dependence but effective pain relief) on cell therapy in SCI. The antinociceptive dose of morphine was determined in rats with SCI through the Hargreaves and naloxone-induced morphine withdrawal tests. The rats were then allocated to 5 groups: laminectomy, SCI, SCI + Morphine, SCI + cell therapy, SCI + Morphine + cell therapy. The antinociceptive dose (5 mg/kg) was administered on days 1, 4, 10, and 13 (i.p.) post-SCI. On day 7, Neural-like stem cells derived from adipose tissue were transplanted intraspinally into the injured animals, and they were monitored for 12 weeks. The outcomes were assessed using the BBB test, somatosensory evoked potential (SSEP), and histology. The BBB test indicated that morphine significantly hindered functional recovery post-cell transplantation compared to animals receiving only cell therapy (p < 0.05). In the SSEP test, the analysis of amplitude and latency of waves did not reveal a significant difference (p > 0.05). The histological results showed that cell therapy reduced the cavity size post-SCI, while morphine had no significant impact on it. Morphine at the antinociceptive dose significantly impairs motor recovery despite cell therapy. Nonetheless, there was no significant difference between groups in terms of sensory pathway outcomes.

Methylphenidate attenuates signs of evoked neuropathic pain in animal model

Methylphenidate is a psychostimulant that increases dopamine and noradrenaline levels. Recent studies have shown that methylphenidate potentiates the effect of morphine and together suppress acute and chronic pain. In clinical practice, methylphenidate has been used as a treatment for ADHD and changes of pain threshold have been noted in these patients. The aim of this study was to determine the effect of methylphenidate in an animal model of peripheral neuropathic pain. Neuropathic pain was modeled by the chronic constriction of the sciatic nerve (CCI) in Wistar rats. We evaluated the effect of methylphenidate (1 mg/kg, s.c.) on evoked pain (reflex tests - plantar test, vonFrey test and operant test - thermal place preference) and on spontaneous pain (conditioned place preference). CCI induced thermal, mechanical and cold hyperalgesia/allodynia. Methyphenidate suppressed mechanical and cold hyperalgesia/allodynia, while had no effect on thermal one. Therefore, methylphenidate seems to be a new potential pharmacotherapy for the treatment of neuropathic pain.

Beyond Amitriptyline: A Pediatric and Adolescent Oriented Narrative Review of the Analgesic Properties of Psychotropic Medications for the Treatment of Complex Pain and Headache Disorders

Children and adolescents with recurrent or chronic pain and headache are a complex and heterogenous population. Patients are best served by multi-specialty, multidisciplinary teams to assess and create tailored, individualized pain treatment and rehabilitation plans. Due to the complex nature of pain, generalizing pharmacologic treatment recommendations in children with recurrent or chronic pains is challenging. This is particularly true of complicated patients with co-existing painful and psychiatric conditions. There is an unfortunate dearth of evidence to support many pharmacologic therapies to treat children with chronic pain and headache. This narrative review hopes to supplement the available treatment options for this complex population by reviewing the pediatric and adult literature for analgesic properties of medications that also have psychiatric indication. The medications reviewed belong to medication classes typically described as antidepressants, alpha 2 delta ligands, mood stabilizers, anti-psychotics, anti-sympathetic agents, and stimulants.