Donepezil provides positive effects to patients treated with gabapentin for neuropathic pain: an exploratory study

Efficacy of donepezil for the treatment of oxaliplatin-induced peripheral neuropathy: DONEPEZOX, a protocol of a proof of concept, randomised, triple-blinded and multicentre trial

Background

The use of oxaliplatin in digestive tract cancers could induce severe peripheral neuropathy (OIPN) decreasing the quality of life of patients and survivors. There is currently, no univocal treatment for these peripheral neuropathies. Donepezil, a reversible inhibitor of cholinesterase, used to treat Alzheimer’s disease and dementia, is reported to have a good safety profile in humans, and preclinical data have provided initial evidence of its effectiveness in diminishing neuropathic symptoms and related comorbidities in OIPN animal models.

Methods

The DONEPEZOX trial will be a proof-of-concept, randomised, triple-blinded, and multicentre study. It will be the first clinical trial evaluating the efficacy and safety of donepezil for the management of OIPN. Adult cancer survivors with OIPN that report sensory neuropathy according to QLQ-CIPN20 sensory score (equivalence of a grade ≥ 2), at least 6 months after the end of an oxaliplatin-based chemotherapy will be included. Eighty patients will be randomly assigned to receive either donepezil or placebo over 16 weeks of treatment. The primary endpoint will be the rate of responders (neuropathic grade decreases according to the QLQ-CIPN20 sensory score) in the donepezil arm. The severity of OIPN will be assessed by the QLQ-CIPN20 sensory scale before and after 16 weeks of treatment. The comparison versus the placebo arm will be a secondary objective. The other secondary endpoints will be tolerance to donepezil, the severity and features of OIPN in each arm before and after treatment, related-comorbidities and quality of life. Fleming’s one-stage design will be used for sample size estimation. This design yields a type I error rate of 0.0417 and power of 91% for a responder rate of at least 30% in donepezil arm. A total of 80 randomized patients is planned.

Discussion

This study will allow, in the case of positive results, to initiate a phase 3 randomized and placebo-controlled (primary endpoint) clinical study to assess the therapeutic interest of donepezil to treat OIPN.

Trial registration

NCT05254639, clincialtrials.gov, Registered 24 February 2022.

Analgesic and preventive effects of donepezil in animal models of chemotherapy-induced peripheral neuropathy: Involvement of spinal muscarinic acetylcholine M2 receptors

BACKGROUND

Donepezil, a cholinesterase inhibitor approved in Alzheimer's disease, has demonstrated analgesic and preventive effects in animal models of oxaliplatin-induced neuropathy. To improve the clinical interest of donepezil for the management and prevention of chemotherapy-induced peripheral neuropathy (CIPN), a broader validation is required in different animal models of CIPN.

METHODS

using rat models of CIPN (bortezomib, paclitaxel, and vincristine), the analgesic and preventive efficacies of donepezil were evaluated on tactile, cold and heat hypersensitivities. The involvement of muscarinic M2 acetylcholine receptors (m2AChRs) in analgesic effects was investigated at the spinal level. The absence of interference of donepezil with the cytotoxic effect of chemotherapy has been controlled in cancer cell lines.

RESULTS

the analgesic efficacy of donepezil was demonstrated for all CIPN models, mainly on tactile hypersensitivity (maximal efficacy at 60 min, p < 0.05 vs. vehicle group). This effect was suppressed by an intrathecal injection of methoctramine (m2AChR antagonist). Regarding preventive effects, donepezil limited tactile hypersensitivity induced by paclitaxel, but not for other CIPN models. Donepezil did not modify the viability of cancer cells or the efficacy of anticancer drugs.

CONCLUSIONS

donepezil had a broad analgesic effect on animal models of CIPN and this effect involved spinal m2AChRs. This work validates the repositioning of donepezil in the management of CIPN.

The efficacy of duloxetine depends on spinal cholinergic plasticity in neuropathic pain model rats

Antidepressants, such as duloxetine, are widely used to treat chronic pain, including neuropathic pain; however, their efficacy is unsatisfactory. In our previous studies, we showed that in a spinal nerve ligation (SNL) rat model, the descending noradrenergic inhibitory system, which involves in the anti-hypersensitivity mechanism of antidepressants, decrease its activity over time following peripheral nerve injury. In this study, we hypothesized that the analgesic effects of duloxetine may diminish following the attenuation of the descending noradrenergic inhibitory system. The analgesic effects of duloxetine in SNL model rats at the early (SNL2W) and chronic (SNL6W) phases following spinal nerve ligation were compared. Male Sprague-Dawley rats were randomly assigned to the SNL2W or SNL6W groups and used to evaluate the anti-allodynic effects of duloxetine using the von Frey filament test. The anti-allodynic effects of duloxetine at a dose of 10 mg/kg were lower in SNL6W rats than in SNL2W rats. Basal noradrenaline concentrations in rat spinal dorsal horns were higher in the SNL6W group than in the SNL2W group, and there was no difference in the increase in spinal noradrenaline concentrations between the 2 groups following duloxetine administration. In addition, we found that duloxetine-induced acetylcholine (ACh) release and choline acetyltransferase (ChAT) expression in the spinal dorsal horn decreased in SNL6W rats. At a dose of 30 mg/kg, duloxetine showed anti-allodynic effects even in SNL6W rats and induced ACh release in the spinal cord. Furthermore, these anti-allodynic effects were completely inhibited by intrathecal atropine (muscarinic antagonist) administration. Moreover, 5 daily intraperitoneal injections of the TrkB agonist, 7,8-dihydroxyflavone (5 mg/kg), not only restored ChAT expression, but also decreased the anti-allodynic effects of duloxetine. These findings suggest that the attenuation of the anti-allodynic effects of duloxetine at the chronic phase of SNL may be due to impaired spinal acetylcholine-mediated analgesia. In addition, the activation of BDNF-TrkB signaling may be beneficial in reversing this impairment.

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The anti-allodynic effect of duloxetine decreases at chronic stage following nerve injury than at early phase.

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There are no differences in the inhibition of noradrenaline reuptake by duloxetine between SNL2W and SNL6W rats.

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The spinal ChAT immunoreactivity and duloxetine-induced spinal ACh release are reduced in SNL6W rats.

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TrkB agonist increases spinal ChAT and restores the attenuation of anti-allodynic effects of duloxetine in SNL6W rats.

Donepezil improves neuropathy through activation of AMPK signalling pathway in streptozotocin-induced diabetic mice

Diabetic neuropathy (DN) is a common complication of diabetes mellitus and is associated with structural changes in the nerves. However, the molecular basis for DN is poorly understood. Adenosine monophosphate activated protein kinase (AMPK) has been shown to regulate the activity of some kinases including protein kinase B (AKT), mitogen-activated protein kinases (MAPK) and mammalian target of rapamycin complex 1 (mTORC1) that represent important signalling pathways modulating the function of peripheral nociceptive neuron. Donepezil can activate AMPK and exerts neuroprotective effects. In this study, streptozotocin (45 mg/kg for 5 Day, i.p.) was used to induce experimental DN. After confirmation of development of neuropathy, mice were randomly distributed into five groups: Group 1; negative control group received saline (0.9%NaCl), Group 2; diabetic mice received saline, Group (3-5); diabetic mice received daily donepezil (1, 2 or 4 mg/kg, p.o.) respectively for 20 days. Mice were then sacrificed under anesthesia then their sciatic nerve and spinal cord were dissected out and processed for biochemical and histopathological studies. Diabetic mice revealed severe histological abnormalities including degenerated neurons in the spinal cord and swollen myelin sheath with inflammatory edema observed in sciatic nerves. In addition, diabetic mice showed reduced expression of p-AMPK in sciatic nerves with consequent activation of AKT/MAPK/4EBP1. A significant upregulation of the N-Methyl-d-aspartate (NMDA) receptors in both cervical and lumbar regions of spinal cord of diabetic mice was also demonstrated. Donepezil, an AMPK activator, blocked the phosphorylation of AKT/MAPK/4EBP1, down regulate the expression of NMDA receptors and reversed hyperalgesia developed in diabetic mice. Therefore, Donepezil could be a potential pharmacological agent for management of DN.

Acetylcholinesterase Inhibitors: Beneficial Effects on Comorbidities in Patients With Alzheimer's Disease

Elderly patients with Alzheimer's disease (AD) and other dementias are at high risk of polypharmacy and excessive polypharmacy for common coexisting medical conditions. Polypharmacy increases the risk of drug-drug and drug-disease interactions in these patients who may not be able to communicate early symptoms of adverse drug events. Three acetylcholinesterase inhibitors (ACHEIs) have been approved for AD: donepezil (Aricept), rivastigmine (Exelon), and galantamine (Razadyne). They are also used off-label for other causes of dementia such as Lewy body and vascular dementia. We here report evidence from the literature that ACHEI treatment, prescribed for cognitive impairment, can reduce the load of medications in patients with AD by also addressing cardiovascular, gastrointestinal, and other comorbidities. Using one drug to address multiple symptoms can reduce costs and improve medication compliance.

Experimental Drugs for Neuropathic Pain

BACKGROUND

Neuropathic pain (NP) is an important public health problem and despite recent progress in the understanding, diagnosis, pathophysiological mechanisms and the treatment of NP, many patients remain refractory to pharmacotherapy.

OBJECTIVE

Currently used drugs have limited efficacy and dose-limiting adverse effects, and thus there is a substantial need for further development of novel medications for its treatment. Alternatively, drugs approved for use in diseases other than NP can be applied as experimental for NP conditions. This paper covers advances in the field of NP treatment.

RESULTS

The prime focus of this paper is on drugs with well-established pharmacological activity whose current therapeutic applications are distinct from NP. These drugs could be a potential novel treatment of NP. Data from preclinical studies and clinical trials on these experimental drugs are presented. The development of advanced methods of genomics enabled to propose new targets for drugs which could be effective in the NP treatment.

CONCLUSION

Experimental drugs for NP can be a treatment option which should be tailor-made for each individual on the basis of pain features, previous therapies, associated clinical conditions, recurrence of pain, adverse effects, contraindications and patients' preferences. At present, there are only some agents which may have potential as novel treatments. Increasing knowledge about mechanisms underlying NP, mechanisms of drug action, as well as available data from preclinical and clinical studies make botulinum toxin A, minocycline, ambroxol, statins and PPAR agonists (ATx086001) promising potential future treatment options.

Molecular, Cellular and Circuit Basis of Cholinergic Modulation of Pain

In addition to being a key component of the autonomic nervous system, acetylcholine acts as a prominent neurotransmitter and neuromodulator upon release from key groups of cholinergic projection neurons and interneurons distributed across the central nervous system. It has been more than forty years since it was discovered that cholinergic transmission profoundly modifies the perception of pain. Directly activating cholinergic receptors or extending the action of endogenous acetylcholine via pharmacological blockade of acetylcholine esterase reduces pain in rodents as well as humans; conversely, inhibition of muscarinic cholinergic receptors induces nociceptive hypersensitivity. Here, we aim to review the considerable progress in our understanding of peripheral, spinal and brain contributions to cholinergic modulation of pain. We discuss the distribution of cholinergic neurons, muscarinic and nicotinic receptors over the central nervous system and the synaptic and circuit-level modulation by cholinergic signaling. AchRs profoundly regulate nociceptive transmission at the level of the spinal cord via pre- as well as postsynaptic mechanisms. Moreover, we attempt to provide an overview of how some of the salient regions in the pain network spanning the brain, such as the primary somatosensory cortex, insular cortex, anterior cingulate cortex, the medial prefrontal cortex and descending modulatory systems are influenced by cholinergic modulation. Finally, we critically discuss the clinical relevance of cholinergic signaling to pain therapy. Cholinergic mechanisms contribute to several both conventional as well as unorthodox forms of pain treatments, and reciprocal interactions between cholinergic and opioidergic modulation impact on the function and efficacy of both opioids and cholinomimetic drugs.

The effect of a combination of gabapentin and donepezil in an experimental pain model in healthy volunteers: Results of a randomized controlled trial

This double-blind, placebo-controlled, 3-period cross-over, 4-treatment option, incomplete block study (ClinicalTrials.gov number NCT01485185), with an adaptive design for sample size re-estimation, was designed to evaluate gabapentin plus donepezil in an established experimental model of electrical hyperalgesia. Thirty healthy male subjects aged 18-55 years were randomized to receive gabapentin 900 mg or gabapentin 900 mg+donepezil 5mg for 2 of the 3 treatment periods, with 50% of subjects randomized to receive placebo (negative control) and 50% to gabapentin 1800 mg (positive control) for the remaining period. Each treatment period was 14 days. Gabapentin or corresponding placebo was administered on Day 13 and the morning of Day 14. Donepezil or corresponding placebo was administered nocturnally from Day 1-13 and the morning of Day 14. Co-primary endpoints were the area of pinprick hyperalgesia (260 mN von Frey filament) and allodynia (stroking by cotton bud) evoked by electrical hyperalgesia on Day 14. Gabapentin 1800 mg (n=14) significantly reduced the area of allodynia vs placebo (n=14; -12.83 cm(2); 95% confidence interval [CI] -23.14 to -2.53; P=0.015) with supportive results for hyperalgesia (-14.04 cm(2); 95% CI -28.49-0.41; P=0.057), validating the electrical hyperalgesia model. Gabapentin+donepezil (n=30) significantly reduced the area of hyperalgesia vs gabapentin 900 mg (n=30; -11.73 cm(2); 95% CI -21.04 to -2.42; P=0.014), with supportive results for allodynia (-6.62 cm(2); 95% CI -13.29-0.04; P=0.052). The adverse event profile for gabapentin+donepezil was similar to the same dose of gabapentin. Data are supportive of further clinical investigation of a gabapentin-and-donepezil combination in patients with an inadequate response to gabapentin.