Opioid resistance in chronic daily headache: a synthesis of ideas from the bench and bedside

Knowing the Enemy Is Halfway towards Victory: A Scoping Review on Opioid-Induced Hyperalgesia

Opioid-induced hyperalgesia (OIH) is a paradoxical effect of opioids that is not consensually recognized in clinical settings. We conducted a revision of clinical and preclinical studies and discuss them side by side to provide an updated and renewed view on OIH. We critically analyze data on the human manifestations of OIH in the context of chronic and post-operative pain. We also discuss how, in the context of cancer pain, though there are no direct evidence of OIH, several inherent conditions to the tumor and chemotherapy provide a substrate for the development of OIH. The review of the clinical data, namely in what concerns the strategies to counter OIH, emphasizes how much OIH rely mechanistically on the existence of µ-opioid receptor (MOR) signaling through opposite, inhibitory/antinociceptive and excitatory/pronociceptive, pathways. The rationale for the maladaptive excitatory signaling of opioids is provided by the emerging growing information on the functional role of alternative splicing and heteromerization of MOR. The crossroads between opioids and neuroinflammation also play a major role in OIH. The latest pre-clinical data in this field brings new insights to new and promising therapeutic targets to address OIH. In conclusion, although OIH remains insufficiently recognized in clinical practice, the appropriate diagnosis can turn it into a treatable pain disorder. Therefore, in times of scarce alternatives to opioids to treat pain, mainly unmanageable chronic pain, increased knowledge and recognition of OIH, likely represent the first steps towards safer and efficient use of opioids as analgesics.

What the pharmacological management of migraine can tell us about the future of migraine patient care

Some of the principles of the pharmacologic management of migraine are echoed in urgent discussions of the future of headache care in the USA and around the world. From adverse events to tolerance, addiction, medication overuse and medication persistence, solutions to the pathophysiologic puzzles, and management difficulties in migraine can be found by paying closer attention to patient reports and by facilitating greater patient involvement in the treatment process. Similarly, listening to the patient as customer in the process of value-based care, so adaptable for the problem of migraine, is the solution to the health care crisis we face in so many countries.

Brain imaging in migraine research

Understanding the pathophysiology and pharmacology of migraine has been driven by astute clinical observations, elegant experimental medicine studies, and importantly by studying highly effective anti-migraine agents in the laboratory and the clinic. Significant progress has been made in the use of functional brain imaging to compliment observational studies of migraine phenotypes by highlighting pathways within the brain that may be involved in predisposition to migraine, modulating migraine pain or that could be sensitive to pharmacological or behavioral therapeutic intervention. In drug discovery, molecular imaging approaches compliment functional neuroimaging by visualizing migraine drug targets within the brain. Molecular imaging enables the selection and evaluation of drug candidates by confirming that they engage their targets sufficiently at well tolerated doses to test our therapeutic hypotheses. Migraine is a progressive disorder. Developing our knowledge of where drugs act in the brain and of how the brain is altered in both episodic migraine (interictal state and ictal state) and chronic migraine are important steps to understanding why there is such differential responsiveness to therapeutics among migraine patients and to improving how they are evaluated and treated.

Tolerance to the beneficial effects of prophylactic migraine drugs: a systematic review of causes and mechanisms

Loss of benefit of a previously effective treatment regimen, also known as tolerance, can be an important barrier to the successful preventive treatment of migraine. We undertook a systematic review of the literature to identify the prevalence and possible mechanisms of drug tolerance in migraine prophylaxis. Results demonstrate that the frequency of tolerance to prophylactic migraine treatment is unknown, but available data support an estimate that it occurs in 1-8% of patients receiving prophylaxis. Four broad types of tolerance were identified that are likely to be relevant to migraine prophylaxis. These are pharmacokinetic, pharmacodynamic, behavioral, and cross tolerance. The mechanisms that underlie these types of tolerance determine whether their effects can be overcome or minimized. For example, certain forms of tolerance may be affected by manipulation of environmental cues associated with drug administration, by the order in which drugs are used, and by the concomitant use of other medications. Many medications used for migraine prophylaxis exert their effects through the endogenous opioid system. The implications of this finding are explored, particularly the parallels between medication overuse headache and tolerance to migraine prophylaxis. Given the many ways in which tolerance to migraine medications may develop, in some ways it is not surprising that migraine-preventive drugs stop working; it is more surprising that in many cases they do not.

Shared mechanisms for opioid tolerance and a transition to chronic pain

Clinical pain conditions may remain responsive to opiate analgesics for extended periods, but such persistent acute pain can undergo a transition to an opiate-resistant chronic pain state that becomes a much more serious clinical problem. To test the hypothesis that cellular mechanisms of chronic pain in the primary afferent also contribute to the development of opiate resistance, we used a recently developed model of the transition of from acute to chronic pain, hyperalgesic priming. Repeated intradermal administration of the potent and highly selective mu-opioid agonist, [d-Ala(2),N-MePhe(4),gly-ol]-enkephalin (DAMGO), to produce tolerance for its inhibition of prostaglandin E(2) hyperalgesia, simultaneously produced hyperalgesic priming. Conversely, injection of an inflammogen, carrageenan, used to produce priming produced DAMGO tolerance. Both effects were prevented by inhibition of protein kinase Cepsilon (PKCepsilon). Carrageenan also induced opioid dependence, manifest as mu-opioid receptor antagonist (d-Phe-Cys-Tyr-d-Trp-Orn-Thr-Pen-Thr-NH(2))-induced hyperalgesia that, like priming, was PKCepsilon and G(i) dependent. These findings suggest that the transition from acute to chronic pain, and development of mu-opioid receptor tolerance and dependence may be linked by common cellular mechanisms in the primary afferent.

Migraine: an overview

The pathophysiology of migraine is not completely understood and continues to be investigated. The complexity of interactions taking place in the sensory neuronal network with the mediation of all different neurotransmitters involved gives the measure of the extreme difficulty connected with the knowledge of migraine pathogenesis and in particular of its cardinal sign. Neuronal components are relevant in migraine pathophysiology: there could be a generalized interictal abnormal excitability of the cerebral cortex in migraine, possibly favoring the occurrence of spreading depression with consequent activation of the trigeminal system. Many theories have been formulated in these last sixty years about the pathogenesis of migraine and other forms of primary headache, but the problem is still far to be fully clarified. The present review is focused on the description of different theories on the migraine pathogenesis. This review is dedicated to the memory of Prof. Alfredo Bianchi.

Excitatory neurotransmitters in brain regions in interictal migraine patients

OBJECTIVE

To examine biochemical differences in the anterior cingulate cortex (ACC) and insula during the interictal phase of migraine patients. We hypothesized that there may be differences in levels of excitatory amino acid neurotransmitters and/or their derivatives in migraine group based on their increased sensitivity to pain.

METHODS

2D J-resolved proton magnetic resonance spectroscopy (1H-MRS) data were acquired at 4.0 Tesla (T) from the ACC and insula in 10 migraine patients (7 women, 3 men, age 43 +/- 11 years) and 8 age gender matched controls (7 women, 3 men, age 41 +/- 9 years).

RESULTS

Standard statistical analyses including analysis of variance (ANOVA) showed no significant metabolite differences between the two subject cohorts in the ACC nor the insula. However, linear discriminant analysis (LDA) introduced a clear separation between subject cohorts based on N-acetyl aspartylglutamate (NAAG) and glutamine (Gln) in the ACC and insula.

CONCLUSION

These results are consistent with glutamatergic abnormalities in the ACC and insula in migraine patients during their interictal period compared to healthy controls. An alteration in excitatory amino acid neurotransmitters and their derivatives may be a contributing factor for migraineurs for a decrease in sensitivity for migraine or a consequence of the chronic migraine state. Such findings, if extrapolated to other regions of the brain would offer new opportunities to modulate central system as interictal or preemptive medications in these patients.

Is migraine a neuropathic pain syndrome?

The understanding of migraine pathophysiology has evolved from the belief that migraine is a vascular disorder, to evidence that better defines migraine as a neurogenic disorder associated with secondary changes in brain perfusion. There is evidence to suggest that the early phase of migraine pain results from neurogenic inflammation affecting cranial blood vessels and dura. Allodynia, hyperalgesia, and expansion of nociceptive fields occur during most well-established migraine attacks. These clinical features of migraine are evocative of those traditionally associated with neuropathic pain. A hypothesis that defines migraine pain as a unique neuropathic pain disorder can imply the potential for neural plasticity and may provide insight into the mechanisms that underlie the transformation of episodic to chronic forms of migraine. The neuropathic pain model of migraine pathophysiology not only paves the way for mechanism-based treatment strategies that can improve the acute and preventive management of migraine attacks, but also opens the door for the discovery of novel therapeutic targets. It also lends momentum to an understanding of clinically intriguing topics such as opiate-induced hyperalgesia and medication-overuse headache (rebound headache), opioid resistance in the treatment of chronic headache, and disease modification in defending against the potential for migraine transformation.

Cost Considerations of Acute Migraine Treatment

OBJECTIVE

To provide medication price data and cost-reducing strategies for the acute treatment of migraine.

METHODS

Retail prices for common acute care medications were found at http://www.drugstore.com. Cost-reduction tactics were obtained from literature searches and clinical experience.

RESULTS

Several strategies can reduce cost without sacrificing treatment outcome. In mild to moderate migraine, low-priced nonsteroidal anti-inflammatory drugs can be used as first-line medications due to their proven efficacy and favorable tolerability. For patients with more severe migraine, implementing a stratified care approach-using migraine-specific medications early in acute treatment-is cost-effective for most patients. Stratified care not only improves outcome and decreases disability, but also reduces cost. Pill splitting and early administration of triptans within an attack enhance their value. Supplying rescue medications, such as opioids, sedatives, and phenothiazines, can prevent emergency department visits. Minimizing multiple dosing of triptans and reducing utilization of expensive health care resources are key factors in reducing the cost of effective migraine treatment. An important affordability factor for patients with co-payments is the number of triptan pills per package. Sumatriptan, naratriptan, and frovatriptan each contain 9 tablets per package, while most other triptan packages contain 6. Current triptan retail prices (per unit) include: Amerge 1 and 2.5 mg, 17.78 dollars; Axert 6.25 and 12.5 mg, 16.31 dollars; Frova 2.5 mg, 13.89 dollars; Imitrex 50 mg, 14.96 dollars; Imitrex 100 mg, 14.41 dollars; Imitrex Nasal Spray 20 mg, 21.61 dollars; Imitrex SQ 6 mg, 50.26 dollars; Maxalt 5 and 10 mg, 15 dollars; Maxalt-MLT 5 and 10 mg, 15 dollars; Relpax 40 mg, 13.58 dollars; Zomig 2.5 mg, 13.67 dollars; Zomig 5 mg, 15.89 dollars; Zomig-ZMT 2.5 mg, 13.67 dollars; and Zomig-ZMT 5 mg, 15.89 dollars.

CONCLUSIONS

Practitioners can optimize the use of health care dollars without compromising quality of care through awareness of cost-saving treatment strategies, as well as price variations among medications.