Pupillary response to methadone challenge in heroin users

Transcranial direct current stimulation of the frontal-parietal-temporal brain areas reduces cigarette consumption in abstinent heroin users

Transcranial direct current stimulation (tDCS) has been demonstrated to modulate neural activity and related brain functions. In clinical studies, tDCS has been shown to reduce craving in various substance use disorders including cocaine, heroin and nicotine. Our previous report suggested that cathodal tDCS on the frontal-parietal-temporal (FPT) brain areas reduced cigarette consumption in moderate smokers. However, whether it is effective in smokers with history of drug use is unknown. This study investigated the effects of bilateral FPT areas cathodal tDCS on smokers with history of heroin use. 22 abstinent heroin users were recruited and randomly assigned to sham group and tDCS group. The sham group received 30 s tDCS treatment and tDCS group received normal tDCS (one trial of 20 min, 1 mA, cathodal electrodes were placed bilaterally on the FPT areas). The average of daily cigarettes consumption was recorded for the week before the tDCS and the following day after tDCS. In addition, pupil light reflex was measured right before and after tDCS treatment. One trial of tDCS stimulation significantly reduced daily cigarette consumption in smokers who had heroin use history. This reducing effect was also observed in heavy smokers. In addition, this effect on cigarette consumption lasted at least 48 h after the stimulation. Furthermore, it has been shown that opiates decrease pupillary size in humans, we found detectable changes of the dynamic pupil light reflex after bilateral tDCS stimulation. These findings suggest that FPT cathodal tDCS may be an effective approach to reduce cigarette craving in heroin users.

A Pilot Study of Automated Pupillometry in the Treatment of Opioid Use Disorder

Introduction/Background:

A rough, visual estimate of pupil size is used in grading the severity of opioid withdrawal. Few studies have examined the clinical utility of more precise automated pupillometry measurements.

Methods:

This prospective cohort study enrolled 27 patients receiving opioid agonist therapy (OAT) to treat cravings or withdrawal during an acute hospitalization. Six sets of automated pupillometry measurements were obtained at regular intervals before and after administration of OAT. Clinical Opiate Withdrawal Scale measurements were performed pre and post OAT. Primary outcomes included pupil size in dark and bright illumination (mm). Latency of the pupillary light response (s), constriction and dilation velocity (mm/s), and percent constriction (%) were secondary outcomes.

Results:

The mean predosing pupil size in dark and bright illumination was 4.33 ± 1.40 mm and 2.96 ± 0.79 mm, respectively. A significantly decreased mean pupil size was first detected at 15 minutes postdosing (4.01 ± 1.34 mm, P = 0.0115 for dark illumination; 2.71 ± 0.72 mm, P = 0.0003 for bright illumination) and this reduction in pupil size persisted at later postdosing timepoints. Those with Clinical Opiate Withdrawal Scale <5 after dosing had a greater decrease in dark pupil size (10.6% ± 13.2 vs 3.2% ± 3.2, P = 0.043). There was no significant change in the remaining pupil reactivity parameters.

Conclusions:

Automated pupillometry demonstrated a small but significant change in mean pupil size that occurred within 15 minutes of OAT dosing and was associated with low withdrawal scores. This pilot may inform future work to incorporate pupillometry measurement into OAT dosing assessments.

Dynamic assessment of the pupillary reflex in patients on high-dose opioids

Background and aims Pupil size and reaction are influenced by opioids, an effect that is not considered to be affected by opioid tolerance. As clinicians have observed patients on high-dose opioids who exhibited seemingly normal pupil sizes, we wanted to dynamically assess the pupillary reflex in cancer patients on high-dose opioids. Methods We performed a dynamic assessment of the pupillary reflex in cancer patients on high-dose opioids and a control group of healthy volunteers using a portable, monocular, infrared pupillometer. We also performed a clinical examination and measured blood concentrations of opioids and their active metabolites. Results Sixty three patients who were on opioids for 2 months (median time) and on an oral morphine equivalent dose of 250 mg (median dose) were investigated. Most patients used more than one opioid. When correcting for age, pupil size in the group that had received no increase of opioid dose over the last 14 days was not significantly different from pupil size in the healthy volunteer group (p = 0.76), while the group that had increased the dose of opioids differed significantly from healthy volunteers (p = 0.006). We found no statistically significant correlation between total oral morphine equivalents and pupillary reactions or between blood opioid or opioid metabolite concentrations and baseline pupillary changes. Conclusion Pupillary changes do take place in patients on opioids. However, tolerance to these changes occurs when medication is not increased over time. Dynamic pupillometry can give additional information about the degree of tolerance to opioids. Implications These findings elucidate previous misconceptions regarding pupillary effects and tolerance to opioids.

The relationship between pupil diameter and other measures of opioid withdrawal during naloxone precipitated withdrawal

BACKGROUND

Understanding mechanisms of physiological opioid withdrawal symptoms can inform treatment strategies. This secondary analysis evaluated the association between mydriasis (dilated pupils), a commonly-assessed opioid withdrawal metric, with self- and observer-rated opioid withdrawal severity.

METHOD

Ninety-five participants with opioid physical dependence were stabilized with morphine before receiving an injection of the opioid antagonist naloxone to precipitate withdrawal. Pupil diameter, the Subjective Opiate Withdrawal Scale (SOWS), and the Clinical Opiate Withdrawal Scale (COWS) were collected at baseline and in 15-minute intervals for 120 min following naloxone administration. Pearson product-moment correlations and linear regressions characterized the relationships between pupil measurements (baseline and peak naloxone-induced) and self- and observer-rated measures of withdrawal. Repeated-measures ANOVAs tested whether self and observer-rated withdrawal severity corresponded to unique patterns in pupil changes.

RESULTS

Baseline pupil diameter significantly correlated with SOWS and COWS peak scores. Peak naloxone-induced pupil diameter significantly correlated with SOWS scores only. Peak changes in pupil from baseline did not correspond to peak changes in self- and observer-rated withdrawal scales.

CONCLUSIONS

This study suggests that pupil diameter measurements were more closely associated with acute opioid withdrawal severity than changes in pupil diameter. Prospective research examining the mechanisms underlying the relationship between pupil diameter and opioid withdrawal severity are warranted.

Influence of Depth of Hypnosis on Pupillary Reactivity to a Standardized Tetanic Stimulus in Patients Under Propofol-Remifentanil Target-Controlled Infusion: A Crossover Randomized Pilot Study

BACKGROUND

Pupillometry allows the measurement of pupillary diameter variations in response to nociceptive stimuli. This technique has been used to monitor the balance between analgesia and nociception. Under general anesthesia, the amplitude of pupillary dilation is related to the amount of administered opioids. The objective of this study was to determine whether at a constant infusion rate of opioids, the pupillary response was influenced by depth of hypnosis assessed by the bispectral index (BIS).

METHODS

Twelve patients (14-20 years) anesthetized for orthopedic surgery were included. Under propofol-remifentanil target-controlled infusion, remifentanil effect site target concentration was fixed at 1 ng/mL. Two measures of pupillary reflex dilation were performed on each patient in a randomized order: one at BIS 55 and one at BIS 25. These levels of BIS were obtained by adjusting propofol target concentration and maintained for 10 minutes before each measure. For each measure, we applied a standardized tetanic stimulation on the patient's forearm (60 mA, 100 Hz, 5 seconds). All measures were performed before the beginning of surgery.

RESULTS

Pupillary dilation was significantly greater at BIS 55 than at BIS 25: 32.1% ± 5.3% vs 10.4% ± 2.5% (mean difference estimate [95% confidence interval]: 21.8% [12.9-30.6], P < .001), without carryover effect (P = .30) nor period effect (P = .52). Hemodynamic parameters and BIS were not modified by the stimulation.

CONCLUSIONS

In patients receiving a constant infusion of remifentanil at a target concentration of 1 ng/mL, pupillary dilation after a standardized tetanic stimulation was influenced by depth of hypnosis assessed by the BIS.

Infant pupillary response to methadone administration during treatment for neonatal abstinence syndrome: a feasibility study

BACKGROUND

Pupil diameter is a frequently assessed objective index of the pharmacodynamic effects of opioids in adults, but to our knowledge has never been examined in infants. Such a measure could improve assessment and treatment of neonates exposed to opioids in utero. The present study examined changes in pupil diameter after opioid administration in opioid-exposed infants who required pharmacological treatment for neonatal abstinence syndrome (NAS) to test the feasibility of using pupil diameter as a measure of opioid effects in these infants.

METHODS

Ten infants (2-7 days old) receiving methadone (0.4-0.5 mg every 12 h) for the treatment of NAS participated. A picture of one of each infant's eyes was taken under controlled illumination conditions with a standard digital camera just prior to dosing and 0-1, 2-4, 5-7, and 8-10h after dosing. The diameters of the pupil and iris were measured and relative pupil diameter (pupil diameter expressed as a percentage of iris diameter) was analyzed.

RESULTS

Mean (±SE) relative pupil diameter decreased significantly after dosing from 41±2% to 29±2%. After dosing, a significant increasing linear trend was observed over time, with values of 29±2%, 33±3%, 38±3%, and 41±3% at 0-1, 2-4, 5-7, and 8-10h after dosing.

CONCLUSIONS

Infant pupils respond to opioid administration in the same sensitive, orderly manner as is commonly observed in adults. Pupil diameter appears to be an objective, sensitive measure of neonatal response to opioids that may be a useful complement to, or perhaps at times a replacement for, observer-rated scale scores.

Intravenous buprenorphine reduces pupil size and the light reflex in humans

The pupillary effects of intravenous buprenorphine were studied in eight nondependent male subjects who reported previous opiate use. Buprenorphine (0.3, 0.6, and 1.2 mg) decreased pupil size, the amplitude of the light reflex, and the velocities of constriction and dilation. Significant pupillary effects occurred within 15 min of the injection and persisted for 24 hr. At 48 hr most measures returned to baseline levels. Generally the magnitude of the effect was not dose related although recovery occurred sooner after the lower dose. The time course of the pupillary effects of buprenorphine exceeds duration of its analgesic and subjective effects. Previous studies have reported that pupillary measures are especially sensitive to the acute effects of full opiate agonists. The results of the present study indicate that buprenorphine, a partial opiate agonist, causes profound and persistent effects on pupillary size and dynamic measures.

Use of naloxone in the assessment of opiate dependence

All subjects participating in an outpatient study comparing treatments for opiate dependence were given a naloxone challenge to document their level of dependence. Subjects were assessed at 0, 10, 20, and 30 minutes following the administration of intramuscular naloxone (0.4 mg) using an opiate withdrawal assessment scale and measurements of pupillary diameter. Subjects' self reports of daily dollar amounts of opiate use and time since last use were also examined for possible correlation with withdrawal scale scores and pupillary measurements. A significant negative correlation was obtained between pupil diameter and time since last reported use of an opiate. Results indicated that the scale was a reliable indicator of opiate dependence. Ways in which it might be improved are discussed.

Buprenorphine-induced pupillary effects in human volunteers

The pupillary effects of the partial opiate agonist buprenorphine were studied in 16 male subjects who were heroin dependent at the time of admission to the study. Sublingual buprenorphine (8 mg) was administered daily for 18 days and continued either daily or on alternate days from study days 19 through 36. On days 37 through 56, all subjects received buprenorphine placebo. Compared to placebo, buprenorphine decreased pupil size and diminished the constriction and dilation velocities of the light reflex. These effects occurred within 5 hours of buprenorphine administration. Following placebo administration during alternate-day dosing of buprenorphine, pupil size increased and constriction and dilation velocities of the light reflex were significantly greater than after buprenorphine administration in the same subjects. This pattern of effects was observed after buprenorphine was discontinued (day 37). The results indicated that buprenorphine has pupillary effects like those of full opiate agonists. The time course of these effects was similar to previously-reported effects of buprenorphine on the electroencephalogram but not to the time course of subjective effects.