A case of stadol dependence

Post-marketing experience with an opioid nasal spray for migraine: lessons for the future

In 1992 a nasal spray formulation of butorphanol, an opioid medication intended for pain relief, was marketed in the USA on an unscheduled basis. Only a few years later, amid widespread reports of abuse and dependence, primarily in migraine patients, its manufacturer voluntarily requested the Food and Drug Administration to reschedule the drug as a Schedule IV narcotic. The events surrounding this episode are reviewed, and four problem areas that might have contributed are identified: (i) inadequate review of previous experience with other formulations of butorphanol; (ii) failure to consider the impact of disease state and drug formulation on the risk of adverse events; (iii) the limited scope of clinical trials prior to approval; and (iv) aggressive marketing efforts. The implications of these lessons for future drug development and post-marketing surveillance in the migraine field are considered.

Butorphanol dependence increases hippocampal kappa-opioid receptor gene expression

Butorphanol is a synthetic opioid agonist/antagonist analgesic agent, which exerts its effects mainly via kappa-opioid receptors. Characterizations of the gene expression levels of the mRNA for and protein levels of the kappa-opioid receptor in different brain regions of rats are essential for investigating possible mechanisms in the development of physical dependence on and withdrawal from butorphanol. Animals were rendered dependent by intracerebroventricular (i.c.v.) infusion of butorphanol (26 nmol/microl/hr) via osmotic minipumps for 3 days. Rats were sacrificed immediately (dependent group) or 7 hr after discontinuation of i.c.v. butorphanol infusion (withdrawal group). Expression levels of the mRNA for the kappa-opioid receptor, as detected by reverse transcription-polymerase chain reaction followed by Southern blot analysis, were significantly increased in the cerebral cortex, striatum, and midbrain, including thalamus, hippocampus, and pons, in animals dependent on butorphanol. In both dependent and withdrawal groups, Western blot analysis of kappa-opioid receptor protein levels showed significant increases in the amygdaloid nucleus, paraventricular thalamus, and thalamus. However, in the withdrawal group, there were significant decreases in the hippocampus and cortical regions, including the frontal, parietal, and temporal cortex. Regional changes in the mRNA for and protein levels of the kappa-opioid receptor focus attention on highly special roles for this receptor in the development of physical dependence on and the expression of withdrawal from butorphanol dependence.

Changes in the brain kappa-opioid receptor levels of rats in withdrawal from physical dependence upon butorphanol

Changes in kappa-opioid receptor levels have been implicated in the development of physical dependence upon and withdrawal from the mixed agonist-antagonist opioid, butorphanol. Immunoblotting analysis was performed to determine the levels of kappa- and mu-opioid receptors in brain regions of rats in withdrawal from dependence upon butorphanol or morphine. Physical dependence was induced by a 72 h i.c.v. infusion with either butorphanol or morphine (26 nmol/microl/h). Withdrawal was subsequently precipitated by i.c.v. challenge with naloxone (48 nmol/5 microl/rat), administered 2 h following cessation of butorphanol or morphine infusion. Immunoblotting analysis of kappa-opioid receptors from butorphanol-withdrawal rats showed significant increases in 11 of 21 brain regions examined, including the nucleus accumbens, amygdala, dorsomedial hypothalamus, hypothalamus, paraventricular thalamus, thalamus, presubiculum, and locus coeruleus, when compared with saline treated, non-dependent controls. In addition, significant reductions were found in the hippocampus and in cortical brain regions, including the parietal cortex and temporal cortex from butorphanol-withdrawal rats. These findings contrasted with those from morphine-withdrawal rats, in which the only changes noted were increases in the thalamus and paraventricular thalamus. Changes in the levels of the mu-opioid receptor protein were observed in 11 of 21 brain regions examined in morphine-withdrawal rats, but only in three of 21 in butorphanol-withdrawal rats. These results implicate a substantive and largely unique role for kappa-opioid receptors in mediation of the development of physical dependence upon, and the expression of withdrawal from, butorphanol, as opposed to the prototypical opioid analgesic, morphine.

Changes of the level of G protein alpha-subunit mRNA by tolerance to and withdrawal from butorphanol

Butorphanol was infused continuously into cerebral ventricle at a constant rate of 26 nmol/microl/h for 3 days, and the withdrawal from opioid was rendered 7 h after the cessation of infusion. The G-protein alpha-subunit has been implicated in opioid tolerance and withdrawal. The effects of continuous infusion of butorphanol on the modulation of G protein alpha-subunit mRNA were investigated by using in situ hybridization techniques. In situ hybridization showed marked changes in the levels of Galpha s during butorphanol tolerance and withdrawal. Specifically, the level of Galpha s mRNA was significantly decreased in almost all areas of brain except hippocampus during the butorphanol withdrawal. It was also decreased in the septum and cerebellar granule layer in butorphanol tolerant rats. The level of Galpha i mRNA was significantly decreased only in the cerebral cortex of butorphanol tolerant rat. However, no such change was noted during the withdrawal from butorphanol. The level of Galpha o mRNA was not changed either in butorphanol tolerant or in the butorphanol withdrawal rats. No alterations were noted in the level of [3H]forskolin binding to adenylyl cyclase in butorphanol tolerant as well as withdrawing rats. The levels of pCREB were significantly elevated in the hippocampus in the butorphanol withdrawal rats. These results suggest that region-specific changes of G protein alpha-subunit mRNA and pCREB without marked changes in the level of adenylyl cyclase may underlie the tolerance to and withdrawal from butorphanol.

Proteomic analysis of phosphotyrosyl proteins in the rat brain: Effect of butorphanol dependence

Butorphanol (17-cyclobutylmethyl-3,14-dihydroxymorphinan) tartrate (Stadol) is a mixed agonist-antagonist opioid analgesic agent that is about five to seven times as potent as morphine in analgesic effects. The chronic use of butorphanol produces physical dependence in humans and animals. Phosphorylation plays a very important role in developing butorphanol dependence; however, global phosphorylation events induced by chronic butorphanol administration have not been reported. The aim of this study is to determine the alteration of tyrosine phosphorylation of brain frontal cortical proteins in butorphanol-dependent rats using a proteomic approach. Dependence was produced by continuous intracerebroventricular (i.c.v.) infusion of butorphanol (26 nmol/microl/hr) for 72 hr via osmotic minipump in rats. Similar patterns of protein expression were detected by two-dimensional electrophoresis (2-DE) in brain frontal cortex of butorphanol-dependent and saline-treated control rats. All 65 phosphotyrosyl (p-Tyr) protein spots detected in pH 3-10 phosphotyrosine 2-DE of control rat brains were detected in butorphanol-dependent rat brains. The densities of most p-Tyr protein spots were increased in butorphanol-dependent rat brains compared to saline-treated control samples. Eighteen additional p-Tyr protein spots were detected in pH 3-10 2-DE images of butorphanol-dependent rat brains. Immobilized pH strips with three different narrow pH ranges were examined to improve the resolution of p-Tyr proteins in 2-DE gels. Fifty-three p-Tyr protein spots were identified as known proteins involved in cell cytoskeleton, cell metabolism, and cell signaling. This proteomic approach can provide useful information for understanding the complex mechanism of butorphanol dependence in vivo.

Enhanced binding of nor-binaltorphimine to kappa-opioid receptors in rats dependent on butorphanol

Autoradiographic characterization of binding for brain kappa(1) ([(3)H]CI-977) and kappa(2) ([(3)H]bremazocine) in the presence of DAMGO ([D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin), DPDPE ([D-Pen(2), D-Pen(5)]-enkephalin), and U-69,593 opioid receptors, in the presence of different concentrations of a selective unlabeled kappa-opioid receptor antagonist, nor-binaltorphimine (nor-BNI), was performed in rats in which dependence on or withdrawal from butorphanol had been established. Dependence was induced by a 72 hr intracerebroventricular (i.c.v.) infusion with butorphanol (26 nmol/microl/hr; butorphanol dependent). Butorphanol withdrawal was produced by terminating the infusion of butorphanol in dependent animals. Responses were studied 7 hr following termination (butorphanol withdrawal). IC(50) values from competition studies were estimated by fitting inhibition curves for both kappa(1)- and kappa(2)-opioid receptor assays. In both dependent and withdrawal groups, the IC(50) values obtained against [(3)H]CI-977 or [(3)H]bremazocine with nor-BNI were decreased (ratios of approximately 0.03-0.21 and approximately 0.05-0.42 vs. control, respectively) in brain regions, including frontal cortex, nucleus accumbens, claustrum, dorsal endopiriform nucleus, caudate putamen, parietal cortex, posterior basolateral amygdaloid nucleus, dorsomedial hypothalamus, hippocampus, posterior paraventricular thalamic nucleus, periaqueductal gray, substantia nigra, superficial gray layer of the superior colliculus, ventral tegmental area, and locus coeruleus, compared with control. These results indicate that, in butorphanol-dependent and butorphanol-withdrawal rats, the brain kappa(1)- and kappa(2)-opioid receptors developed a supersensitivity to antagonist binding.

Butorphanol dependence and withdrawal decrease hippocampal kappa 2-opioid receptor binding

The present study examines the degree and distribution of alterations in the expression of kappa-opioid receptor subtypes using a model of chronic intracerebroventricular (i.c.v.) infusion of butorphanol. Autoradiographic characterization of binding for brain kappa(1) ([3H]CI-977)-, kappa(2) ([3H]bremazocine in the presence of DAMGO, DPDPE, and U-69,593)- and total kappa ([3H]bremazocine in the presence of only DAMGO and DPDPE)-opioid receptors was performed. Dependence was induced by a 72 h i.c.v. infusion with butorphanol (26 nmol/microl per hour) (butorphanol-dependent). Butorphanol withdrawal was produced by terminating the infusion of butorphanol in dependent animals. Responses were studied 7 h following termination (butorphanol-withdrawal). During both dependence and withdrawal phases, the binding signals for both kappa(1)- and kappa(2)-opioid receptors were significantly increased in certain regions, with especially marked increases in the frontal cortex, nucleus accumbens, parietal cortex, dorsomedial hypothalamus, ventral tegmental area and locus coeruleus. In contrast, a highly specific decrease in kappa(2)-, but increase in kappa(1)-, opioid receptor binding was noted in the hippocampus of rats in both butorphanol-dependent and-withdrawal groups. Therefore, alterations in kappa(1)- and kappa(2)-opioid receptors in the hippocampus may be differently involved in both adaptation to and recovery from chronic exposure to a mixed agonist/antagonist opioid analgesic. These results further illustrate the regional distribution of changes in binding characteristics of rat brain kappa(1)- and kappa(2)-opioid receptor subtypes in an established model of butorphanol dependence and withdrawal.

The bindings of [3H]muscimol and [3H]flunitrazapam are elevated in discrete brain regions of butorphanol-withdrawal rats

We have investigated the effects of continuous infusion of butorphanol on the modulation of GABA(A) receptor binding. Butorphanol was infused continuously into intracerebroventricle (ICV) at a constant rate of 26 nmol/microl/h for 3 days, and the withdrawal from opioid was rendered 7 h after the cessation of infusion. The GABA(A) receptor bindings in rat brain slices were analyzed by quantitative autoradiography using [3H]muscimol and [3H]flunitrazepam. In the rats withdrawn from butorphanol, the levels of [3H]muscimol binding were significantly elevated in cortex, thalamus, and part of the hippocampus. The levels of [3H]flunitrazepam binding were elevated in almost all of brain regions including cortex, caudate putamen, thalamus, hippocampus, brainstem, and cerebellum in the rats withdrawn from butorphanol. The levels of binding of either [3H]muscimol or [3H]flunitrazepam were not changed in the rats tolerant to butorphanol. However, the activity of GABAergic neuron was not found to have been modulated by butorphanol withdrawal, because the level of glutamic acid decarboxylase was not changed markedly either in rats that were tolerant to or withdrawn from butorphanol by Western blot and immunohistochemical data. These results suggest that the withdrawal from butorphanol infusion markedly elevates the binding of [3H]muscimol and [3H]flunitrazepam throughout the brain in a region-specific manner, and that the regulatory mechanisms in butorphanol tolerance and withdrawal may be different.

Modulation of NMDA receptor subunit mRNA in butorphanol-tolerant and -withdrawing rats

The NMDA receptor has been implicated in opioid tolerance and withdrawal. The effects of continuous infusion of butorphanol on the modulation of NMDA receptor subunit NR1, NR2A, NR2B, and NR2C gene expression were investigated by using in situ hybridization technique. Continuous intracerebroventricular (i.c.v.) infusion with butorphanol (26 nmol/microl/h) resulted in significant modulations in the NRI, NR2A, and NR2B mRNA levels. The level of NR1 mRNA was significantly decreased in the cerebral cortex, thalamus, and CA1 area of hippocampus in butorphanol tolerant and withdrawal (7 h after stopping the infusion) rats. The NR2A mRNA was significantly decreased in the CA1 and CA3 of hippocampus in tolerant rats and increased in the cerebral cortex and dentate gyrus in butorphanol withdrawal rats. NR2B subunit mRNA was decreased in the cerebral cortex, caudate putamen, thalamus, CA3 of hippocampus in butorphanol withdrawal rats. No changes of NR1, NR2A, NR2C subunit mRNA in the cerebellar granule cell layer were observed in either butorphanol tolerant or withdrawal rats. Using quantitative ligand autoradiography, the binding of NMDA receptor ligand [3H]MK-801 was increased significantly in all brain regions except in the thalamus and hippocampus, at the 7 hr after stopping the butorphanol infusion. These results suggest that region-specific changes of NMDA receptor subunit mRNA (NR1 and NR2) as well as NMDA receptor binding ([3H]MK-801) are involved in the development of tolerance to and withdrawal from butorphanol.

The role of glutamate in physical dependence on opioids

The present review will evaluate the interactions between kappa-opioid receptors and glutamate within the locus coeruleus (LC) during the development of opioid dependence and on expression of withdrawal from dependence on opioids. Hyperactivity of noradrenergic neurons in the LC has been proposed to play a critical role in the physiological and behavioral responses that comprise opioid withdrawal. Several studies indicate that the excitatory amino acid system, in particular, glutamate and its receptors, participate in both the withdrawal-associated increase in LC neuronal activity and the expression of opioid withdrawal behaviors. Most studies on opioid dependence have focused on the prototypical opioid morphine, which produces its physical dependence through agonist actions at the mu-opioid receptor. Butorphanol (Stadol), which exhibits a markedly different profile of opioid receptor activity than does morphine, produces its physical dependence primarily through actions at the kappa-opioid receptor. Studies from our laboratories using a rodent model in which butorphanol administration induces dependence indicate further that the kappa-opioid receptor is an important regulator of glutamate release within the LC. Glutamate exerts actions within the LC that mediate expression of behavioral symptoms of butorphanol withdrawal.

Mu- and delta-opioid receptor antagonists precipitate similar withdrawal phenomena in butorphanol and morphine dependence

The relative involvement of mu- and delta-opioid receptors in the mediation of butorphanol-, as compared to morphine-, dependence was examined with the use of highly selective antagonists at mu- and delta-opioid receptors. Extracellular fluid levels of glutamate (Glu) and aspartate (Asp) were measured within the pontine locus coeruleus following precipitation of withdrawal from dependence on either butorphanol or morphine in conscious Sprague-Dawley rats. Dependence was induced by intracerebroventricular (i.c.v.) infusion of butorphanol (26 nmol/mu l/h), morphine (26 nmol/mu l/h) or saline vehicle (1 mu l/h) for 3 days by means of an osmotic minipump. Microdialysis probes (2 mm tip) were inserted into the locus coeruleus 24 h before precipitation of withdrawal by i.c.v. injection of either the mu-opioid receptor antagonist, D-Pen-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP; 48 nmol/5 mu l or 48 nmol/5 mu l), or the delta-opioid receptor antagonist, naltrindole (17-cyclopropy;methyl-6,7-dehydro-4,5-epoxy-3, 14-dihydroxy-6,7,2'3'-indolmorphinan hydrochloride; 48 nmol/5 mu l or 100 nmol/5 mu l). Baseline levels of Glu ranged from 9.59 + or - 1.27 to 12.84 + or - 3.01 mu M in the various treatment groups. Levels of Asp were similar. Precipitation of withdrawal by CTOP elicited significant increases of Glu and Asp in both morphine- and butorphanol-dependent rats. Maximal increases in Glu of 425% and 258% above baseline levels were elicited in the first 15 min microdialysis sample following i.c.v. injection of CTOP in morphine- and butorphanol-dependent rats, respectively. Behavioral signs of withdrawal were greater in morphine than butorphanol-dependent groups. The i.c.v. treatment with naltrindole elicited increases in Glu and Asp that were similar, although less marked, than those precipitated by CTOP treatment. Administration of naltrindole produced equivalent signs of withdrawal in both morphine- and butorphanol-dependent rats. Withdrawal from dependence on both morphine and butorphanol is characterized by elevations in coerulear levels of excitatory amino acids. Responses elicited following the use of selective mu- and delta-opioid receptor antagonists to precipitate withdrawal suggest that the role played by these receptors in mediation of the signs and symptoms of withdrawal do not differ greatly between butorphanol- and morphine-dependent rats.

Increased locus coeruleus glutamate levels are associated with naloxone-precipitated withdrawal from butorphanol in the rat

Extracellular fluid levels of glutamate were measured in the locus coeruleus during butorphanol (a mixed agonist at mu-, delta-, and kappa-opioid receptors) withdrawal by using microdialysis in conscious butorphanol-dependent Sprague-Dawley rats. Guide cannulae were implanted chronically and rats were given intracerebroventricular (i.c.v.) infusions of butorphanol (26 nmol/1 microliter/hr) or saline (1 microliter/hr) for 3 days. Microdialysis probes (2 mm tip) were inserted into the locus coeruleus 24 hr before precipitation of withdrawal by i.c.v. injection of naloxone (48 nmol/5 microliters). A separate series of rats was rendered dependent by peripheral injection of butorphanol (20 mg/kg, s.c., b.i.d.) for 5 days and naloxone (5 mg/kg, i.p.) was given to precipitate withdrawal. Single injections of butorphanol (26 nmol/5 microliters, i.c.v.) had no effect on the extracellular fluid levels of glutamate, compared to rats injected with vehicle. Behavioral evidence of withdrawal was detected following naloxone challenge in butorphanol-dependent rats (both i.c.v. and s.c. models), but not in non-dependent, vehicle-treated rats. Significant increases (P < 0.05) in levels of glutamate were noted after naloxone-precipitated withdrawal only in the butorphanol group. The glutamate levels in the locus coeruleus increased from 8.37 +/- 2.01 before, to 21.93 +/- 4.58 microM in the first 15 min sample following i.c.v. injections of 48 nmol/5 microliters naloxone and from 10.84 +/- 1.74 before, to 26.01 +/- 6.19 microM in the 15-30 min sample following i.p. injections of 5 mg/kg naloxone in the butorphanol-dependent rats, respectively. These results provide direct evidence to support the role of excitatory amino acids within the locus coeruleus in butorphanol withdrawal.

The physical dependence liability of butorphanol: a comparative study with morphine

In these studies, the physical dependence liability of butorphanol, a mixed 'agonist/antagonist' opioid analgesic, was compared to that of morphine. Male, Sprague-Dawley rats received i.c.v. infusions of saline (1 microliter/h), or an equimolar dose of butorphanol or morphine (52.3 nmol/h) for 3 days. The physical dependence liabilities of these two compounds were then compared by assessing both behavioral withdrawal signs and weight loss following naloxone-precipitated withdrawal. Body weight loss was also evaluated following abrupt (cessation of infusion) withdrawal from butorphanol or morphine. In animals receiving i.c.v. infusions of butorphanol or morphine, naloxone administration (5 mg/kg s.c.) induced an equivalent degree of body weight loss compared to saline-treated animals. In addition, the ED50 of naloxone to produce wet shakes, escape behavior, teeth chattering, urination and defecation was equivalent in rats receiving butorphanol or morphine. Infusions of butorphanol or morphine also produced an equivalent degree of weight loss in animals undergoing abrupt withdrawal. These results demonstrate then that a substantial degree of physical dependence had developed in rats which received a large dose of butorphanol.