Clonidine in migraine prophylaxis

Consensus of the Brazilian Headache Society (SBCe) for prophylactic treatment of episodic migraine: part II

BACKGROUND

Migraine affects 1 billion people worldwide and > 30 million Brazilians; besides, it is an underdiagnosed and undertreated disorder.

OBJECTIVE

The need to disseminate knowledge about the prophylactic treatment of migraine is known, so the Brazilian Headache Society (SBCe, in the Portuguese acronym) appointed a committee of authors with the objective of establishing a consensus with recommendations on the prophylactic treatment of episodic migraine based on articles from the world literature as well as from personal experience.

METHODS

Meetings were held entirely online, with the participation of 12 groups that reviewed and wrote about the pharmacological categories of drugs and, at the end, met to read and finish the document. The drug classes studied in part II of this Consensus were: antihypertensives, selective serotonin reuptake inhibitors, serotonin and norepinephrine reuptake inhibitors, calcium channel blockers, other drugs, and rational polytherapy.

RESULTS

From this list of drugs, only candesartan has been established as effective in controlling episodic migraine. Flunarizine, venlafaxine, duloxetine, and pizotifen were defined as likely to be effective, while lisinopril, enalapril, escitalopram, fluvoxamine, quetiapine, atorvastatin, simvastatin, cyproheptadine, and melatonin were possibly effective in prophylaxis of the disease.

CONCLUSIONS

Despite an effort by the scientific community to find really effective drugs in the treatment of migraine, given the large number of drugs tested for this purpose, we still have few therapeutic options.

Other Preventive Anti-Migraine Treatments: ACE Inhibitors, ARBs, Calcium Channel Blockers, Serotonin Antagonists, and NMDA Receptor Antagonists

PURPOSE OF REVIEW

Migraine causes more years of life lived with disability than almost any other condition in the world and can significantly impact the lives of individuals with migraine, their families, and society. The use of medication for the prevention of migraine is an integral component to reducing disability caused by migraine. There are many different drug classes that have been investigated and shown efficacy in migraine prophylaxis. This article examines several of the classes of medications that are used for migraine preventive treatment, specifically, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, calcium channel blockers, serotonin antagonists, alpha-adrenergic agonists, and N-methyl-D-aspartic acid receptor antagonists.

RECENT FINDINGS

There have been randomized control trials investigating medications in these drug classes since the most recent guidelines for migraine prevention in adults were published by the American Academy of Neurology, American Headache Society, and the Canadian Headache Society. In these investigations, enalapril, candesartan, and memantine all demonstrated efficacy for migraine prevention. The evidence for these and the aforementioned drug classes are reviewed. When oral medications are being selected for migraine prevention, comorbid and coexistent medical conditions, concomitant medications, patient preference, and pregnancy and breast-feeding plans should be considered. Within the drug classes discussed, memantine and candesartan have a moderate level of evidence for efficacy.

Effect of sympathetic and parasympathetic mediators on the release of calcitonin gene-related peptide and prostaglandin E from rat dura mater, in vitro

Although not without controversy, an influence of the autonomic nervous system in headache is a matter for current debate. A possible contact site of autonomic and sensory nerves is the dura mater, where they form a dense network accompanying blood vessels. We investigated interactions between autonomic and nociceptive fibres by measuring release of calcitonin gene-related peptide (CGRP) and prostaglandin E2 (PGE2) from the dura mater, in vitro. The parasympathomimetic agent carbachol did not change basal release of CGRP or PGE2, whereas it diminished release induced by a mixture of inflammatory mediators. Norepinephrine did not change induced release of CGRP or PGE2, nor basal release of CGRP. However, basal release of PGE2 was enhanced by norepinephrine, and this enhancement was reduced by serotonin through 5-HT(1D) receptors. We conclude that sympathetic transmitters may control nociceptor sensitivity via increased basal PGE2 levels, a possible mechanism to facilitate headache generation. Parasympathetic transmitters may reduce enhanced nociceptor activity.

Activation of α2-adrenoreceptors suppresses the excitability of C1 spinal neurons having convergent inputs from tooth pulp and superior sagittal sinus in rats

The aim of the present study was to test the hypothesis that activation of alpha(2)-adrenoreceptors modulates the excitability of C1 neurons having convergent inputs from both the tooth pulp (TP) and the superior sagittal sinus (SSS), by using the microiontophoretic techniques of drug application and immunohistochemical approaches. Extracellular single-unit recordings were made from 38 C1 neurons responding to electrical stimulation of TP under pentobarbital-anesthetized rats. Seventy-one percent of C1 neurons (27/38) that responded to TP stimulation also responded to electrical stimulation of the SSS. In these neurons, L: -glutamate-evoked C1 neuronal discharge firings were increased in a dose-dependent manner. The mean glutamate-evoked firing rates were dose-dependently inhibited after microiontophoretic application of clonidine (alpha(2)-adrenoreceptor/imidazoline I(1) receptor agonist). The inhibition of glutamate-evoked C1 mean firings by clonidine was antagonized by the co-application of idazoxan (alpha(2)-adrenoreceptor/imidazoline I(2) receptor antagonist), yohimbine (alpha(2)-adrenoreceptor) but not the alpha(1)-adrenoreceptor antagonist, prazosin with affinity for alpha(2B)- and alpha(2C)-adrenoreceptors. The mean spontaneous discharge frequencies were significantly inhibited by the microiontophoretic application of clonidine and this inhibition was reversed by the co-application of idazoxan, yohimbine. Microiontophoresis of clonidine also resulted in a reduction of TP-/SSS-evoked activity and this effect was reversed by the co-application of yohimbine. Immunoreactivity for alpha(2A)-adrenoreceptor was found in the superficial layers of I-III in the C1 region. These results suggest that alpha(2)-adrenoreceptor agonist clonidine inhibits the excitability of C1 neurons having convergent inputs from TP and SSS afferents, and that the activation of alpha(2A)-adrenoreceptors onto C1 dorsal horn neurons may contribute as a useful therapeutic target for the alleviation of trigeminal referred pain associated with migraine and tooth pain.

Migraine: preventive treatment

Migraine is a common episodic headache disorder. A comprehensive headache treatment plan includes acute attack treatment to relieve pain and impairment and long-term preventive therapy to reduce attack frequency, severity, and duration. Circumstances that might warrant preventive treatment include: (i) migraine that significantly interferes with the patient's daily routine despite acute treatment; (ii) failure, contraindication to, or troublesome side-effects from acute medications; (iii) overuse of acute medications; (iv) special circumstances, such as hemiplegic migraine; (v) very frequent headaches (more than two a week); or (vi) patient preference. Start the drug at a low dose. Give each treatment an adequate trial. Avoid interfering, overused, and contraindicated drugs. Re-evaluate therapy. Be sure that a woman of childbearing potential is aware of any potential risks. Involve patients in their care to maximize compliance. Consider co-morbidity. Choose a drug based on its proven efficacy, the patient's preferences and headache profile, the drug's side-effects, and the presence or absence of coexisting or co-morbid disease. Drugs that have documented high efficacy and mild to moderate adverse events (AEs) include beta-blockers, amitriptyline, and divalproex. Drugs that have lower documented efficacy and mild to moderate AEs include selective serotonin reuptake inhibitors (SSRIs), calcium channel antagonists, gabapentin, topiramate, riboflavin, and non-steroidal anti-inflammatory drugs.

The effect of adrenergic compounds on neurogenic dural vasodilatation

The pharmacology of neurogenic trigeminovascular vasodilator responses in the dura mater is of interest for understanding the pathophysiology of migraine and to develop new therapies for this disabling common condition. Aminergic mechanisms have been implicated in migraine through direct study of amines in patients, and by inference from the pharmacology of many effective anti-migraine compounds, particularly preventative agents. This study used intravital microscopy to assess the role of aminergic transmission in neurogenic dural vasodilatation (NDV) by measuring directly the diameter of dural arteries in sodium pentobarbitone anaesthetised rats. Electrical stimulation of a closed cranial window produces, by local depolarisation of nerves, dural vessel dilation that is monitored continuously on-line using video-microscopy and a video dimension analyser. This dural vasodilatation was not affected by pre-treatment with an alpha1-adrenoceptor agonist (phenylephrine, 1 and 5 microg/kg), or antagonist (corynanthine, 1 and 2 mg/kg), nor by an alpha2-adrenoceptor agonist (UK14,304, 5 microg/kg) or antagonist (yohimbine, 1 and 3 mg/kg). Similarly, we saw no effect of beta-adrenoceptor blockade (propranolol, 1 and 3 mg/kg). The lack of an inhibitory effect of UK14,304 the model of neurogenic dural vasodilation contrasts with its effect in neurogenic dural plasma protein extravasation model. The lack of inhibition of beta-adrenoceptor antagonists in the neurogenic vasodilatation model contrasts with their usefulness as migraine prophylactics, and suggests that their mechanism of action in migraine is unlikely to be through sensory trigeminal fibre terminals at the neurovascular junction. Moreover, the data indicate that the adrenergic system does not play a significant role in neurogenic dural vasodilation.

Migraine prophylactic drugs: proof of efficacy, utilization and cost

OBJECTIVES

In order to understand the pattern of utilization of migraine prophylactic drugs by US physicians, we reviewed the scientific rigor of published trials of anti-migraine medications, assessed their cost, and tested the correlation, if any, between utilization, scientific rigor and cost.

MATERIALS AND METHODS

Scientific rigor of published reports. We identified all placebo-controlled, randomized, double-blind trials of migraine prophylactic agents through Medline search, major Headache textbooks and proceedings of major scientific meetings where headache-related topics are discussed. We excluded trials that did not include placebo treatment during the active phase of the study. The trials were reviewed and rated for scientific rigor using a 5-point scale (scientific score [ss]; 1 = low, 5 = good), blinded to the physicians' utilization data and cost of the drugs. Studies that did not show benefit of the active drug over placebo were scored -1 to -5, thus allowing for the reverse logic of negative studies. US physicians utilization. Neurologists and primary care physicians (PCP) completed phone-mail-phone questionnaires which inquired about first and second choices of migraine prophylaxis. These choices were averaged to obtain a weighted average percent usage of each drug. Cost. The average wholesale price (AWP) of each drug was obtained from data published by Adelman and Von Seggern, and from the Amerisource (7/9/96) catalog.

STATISTICAL ANALYSIS

Spearman's correlation coefficient was used to assess the relationship between the average ss, physician use, and cost of each drug.

RESULTS

Propranolol (ss = 1.44), amitriptyline (ss = 2.33) and verapamil (ss = 1.00) were the three preferred migraine prophylactic drugs by both neurologists and PCPs. Approximately 10% of neurologists said that divalproex (ss = 3.75) would be their first or second choice. The selective serotonin reuptake blockers were favored by 13.21% of PCPs. All other prophylactic drugs were felt to be first or second line of treatment by less than 10% of either neurologists or PCPs. Except for one study (ss = 1) that showed that propranolol reduced the migraine frequency by 76% over placebo, trials of the three most preferred medications failed to demonstrate that the active drug is > 50% better than placebo, i.e. the difference in headache frequency when on placebo vs active drug is > 50%. Of the drugs available in the United States, flurbiprofen and metoprolol achieved the best ss (5.00 and 4.33, respectively) but their efficacy over placebo (23% and 14-33%, respectively) and cost ($67.2 and $65.6) were unfavorable. Neurologists and PCPs chose migraine prophylaxis on the basis of scientific merit (r = 0.644, p = 0.018; r = 0.576, p = 0.05, respectively) but not cost (r = -0.254, p = 0.45; r = -0.255, p = 0.455).

CONCLUSION

The three most commonly chosen migraine prophylactic agents have not been shown irrefutably to prevent migraine. Furthermore, their benefit, if any, does not exceed 50% over placebo. The well-conducted recent trials that demonstrated the efficacy of divalproex in migraine prevention are steps in the right direction of finding the "ideal migraine preventative agent". Until that drug is discovered, it is difficult to argue that one migraine prophylactic medication is superior to another and accordingly should be used as a first line of treatment.

Clonidine poisoning in Jefferson County, Alabama

STUDY OBJECTIVE

To describe the epidemiology of clonidine-related hospitalization in children, to evaluate the efficacy of naloxone, and to review the clinical effects of clonidine toxicity.

METHODS

This was a retrospective analysis in an urban teaching pediatric emergency department with an annual census of 55,000 involving 80 children younger than 6 years who were admitted for clonidine ingestion during a 6-year period.

RESULTS

Clonidine commonly belonged to the patient's grand-mother (54%). Black children were twice as likely to be hospitalized for clonidine ingestion than white children compared with children hospitalized for any injury. Average time to onset of symptoms was 35 minutes. Decreased level of consciousness was the most common presenting symptom (96%). Mean ED vital signs were systolic blood pressure, 102 mm Hg; pulse, 98; respirations, 25 (six patients intubated); and temperature, 36.6 degrees C, Naloxone was administered to 49% of patients, 84% of whom demonstrated no response.

CONCLUSION

Clonidine ingestion is endemic in our area. Serious clinical effects mandate that all children with clonidine ingestion be triaged to a health care facility. Naloxone as an antidote for clonidine remains controversial.

Effect of nadolol on flushing reactions in rosacea

The effect of nadolol versus placebo on both flushing provoked in a laboratory setting and spontaneous flushing was studied in 15 patients with erythematous telangiectatic rosacea. The intensity of the flushing reactions was assessed in the laboratory by the cutaneous perfusion index method with laser-Doppler velocimetry. No effect of nadolol on the flushing reactions provoked in the laboratory was detected.

Metoprolol v. clonidine in the prophylactic treatment of migraine

In a double-blind, cross-over trial, the migraine prophylactic effect of the beta 1-adrenoceptor antagonist metoprolol was compared with that of clonidine. The dosage of metoprolol was 50 mg b.i.d. and of clonidine 50 micrograms b.i.d. Thirty-one patients were included; twenty-three completed the entire study. Six patients withdrew during clonidine treatment, one during metoprolol treatment and one during the wash-out period (placebo). Metoprolol had a significantly better migraine prophylactic effect than clonidine regarding such parameters as the attack frequency, the number of migraine days and the sum of intensity score. Compared to baseline (placebo), metoprolol decreased these parameters, while clonidine did not. Metoprolol, but not clonidine, also reduced the acute consumption of analgesics. No differences were found as regards side effects.

The diagnosis and management of headaches in childhood

Chronic headaches are relatively common in children and adolescents. The majority of these are benign and do not reflect organic pathology. Diagnosis can usually be made by careful history and physical examination, and extensive laboratory investigations are rarely required. Most children can be managed with reassurance, simple analgesics, and mild sedation. For more severe cases, particularly of migraine, effective pharmacologic agents are available. The prognosis is favorable. Very few of these children go on to develop significant intracranial pathology, and the majority will remit spontaneously. A significant number, however, do have chronic headaches in adult life.

Clonidine overdose: report of six cases and review of the literature

Clonidine poisoning usually causes depressed sensorium, hypotension, and bradycardia. Some patients manifest respiratory depression and miosis simulating narcotic overdose. Supportive care with judicious administration of intravenous fluids, occasionally supplemented by a dopamine infusion, usually reestablished adequate blood pressure. Tolazoline, an alpha-blocker, may reverse clonidine's effects should other efforts fail. Atropine should be used if bradycardia is hemodynamically significant. With massive overdose, clonidine's partial alpha-agonist properties may predominate, resulting in marked hypertension requiring cautious therapy. The experience at Parkland Memorial Hospital with clonidine overdose in six patients demonstrates the myriad of clinical presentations possible.

Inhibition of neurosympathetic cerebroarterial constriction by clonidine in cats

In cats anaesthetized with chloralose the cervical sympathetic nerves were separated from the vagosympathetic trunk and severed. Bilateral preganglionic electrical stimulation of the efferent sympathetic stumps induced rate-dependent decrements in cerebrospinal fluid pressure measured in the cerebral lateral ventricle. Intravenous injection of 3, 10, and 30 micrograms/kg clonidine caused a dose-related shift in threshold and inhibition of the pressure decrease particularly at lower rates of stimulation. Intravenous infusion of 3.75 micrograms/kg . min yohimbine for 30 min reduced the inhibitory effect of 30 micrograms/kg clonidine i.v. Intravenous injection of 5 mg/kg phentolamine reduced the depressor effect at all rates of electrical sympathetic stimulation. In another group of cats craniotomy was performed and the diameter of pial arteries (0.1-0.2 mm) was measured with an eyepiece micrometer under the microscope. Bilateral electrical stimulation of the sympathetic nerves decreased the artery diameter by 16%. This effect was diminished by 30 micrograms/kg clonidine i.v. Because of the characteristic shift of the frequency-response curve caused by clonidine and the antagonistic effect of yohimbine it is assumed that clonidine inhibits sympathetic neurotransmission in pial arteries by activation of prejunctional alpha-adrenoceptors. The inhibitory effect of clonidine in neurosympathetic transmission might explain the efficacy of the drug in the treatment of migraine.