Buprenorphine: a new potent long-acting synthetic analgesic. Comparison with morphine

Effect of addition of buprenorphine or dexamethasone to levobupivacaine on postoperative analgesia in ultrasound guided transversus abdominis plane block in patients undergoing unilateral inguinal hernia repair: a prospective randomized double blind controlled trial

BACKGROUND

The transversus abdominis plane (TAP) block is an effective technique to block the thoracolumbar nerves innervating the anterolateral abdominal wall. This study was conducted to evaluate the analgesic efficacy and opioid consumption with the use of perineural buprenorphine or dexamethasone in TAP blocks after unilateral inguinal hernioplasties.

METHODS

This prospective, randomized, double-blinded, placebo-controlled study enrolled 93 patients scheduled for unilateral inguinal hernioplasty, followed by an ultrasound-guided TAP block. The participants were randomized into 3 groups (31 patients each). Group L received 20 ml 0.25% levobupivacaine + 1 ml normal saline (NS); group LB, 20 ml 0.25% levobupivacaine + 0.3 mg (1 ml) buprenorphine; and group LD, 20 ml 0.25% levobupivacaine + 4 mg (1 ml) dexamethasone. The patients were observed postoperatively for 24 h for first rescue analgesic requirement, total rescue analgesic consumption, and pain scores on the numeric rating scale (NRS).

RESULTS

The time to first rescue analgesic requirement was significantly longer in Group LB than in groups LD and L (688.87 ± 36.11 min, 601.45 ± 39.85 min, and 383.06 ± 36.21 min, respectively; P < 0.001). The mean total tramadol consumption in the first 24 h was the lowest in group LB (P < 0.001, L vs. LB / LD). Groups LB and LD displayed significantly lower NRS scores than group L (P < 0.001 both).

CONCLUSIONS

Levobupivacaine with perineural buprenorphine in a TAP block after unilateral open inguinal hernioplasty facilitates prolonged analgesia and reduced requirement for rescue analgesics compared to perineural dexamethasone, without significant side effects.

Treating Chronic Pain: An Overview of Clinical Studies Centered on the Buprenorphine Option

The buprenorphine receptor binding profile is unique in that it binds to all three major opioid receptors (mu, kappa, delta), and also binds to the orphan-like receptor, the receptor for orphanin FQ/nociceptin, with lower affinity. Within the mu receptor group, buprenorphine analgesia in rodents is dependent on the recently discovered arylepoxamide receptor target in brain, which involves a truncated 6-transmembrane mu receptor gene protein, distinguishing itself from morphine and most other mu opioids. Although originally designed as an analgesic, buprenorphine has mainly been used for opioid maintenance therapy and only now is increasingly recognized as an effective analgesic with an improved therapeutic index relative to certain potent opioids. Albeit a second-, third-, or fourth-line analgesic, buprenorphine is a reasonable choice in certain clinical situations. Transdermal patches and buccal film formulations are now commercially available as analgesics. This review discusses buprenorphine pharmacodynamics and pharmacokinetics, use in certain populations, and provides a synopsis of systematic reviews and randomized analgesic trials. We briefly discuss postoperative management in patients receiving buprenorphine maintenance therapy, opioid equivalence to buprenorphine, rotations to buprenorphine from other opioids, and clinical relevance of buprenorphine-related QTc interval changes.

Transdermal buprenorphine for moderate chronic noncancer pain syndromes

Introduction: Chronic noncancer pain has remained a challenging clinical problem. Opioid analgesics are effective, but they are known to be associated with opioid use disorder and potentially treatment-limiting side effects. Buprenorphine is a Schedule III synthetic opioid in the USA with a chemical structure similar to that of morphine but with a longer duration of action, greater potency, and other unique pharmacological attributes. Its role in treatment of chronic noncancer pain may be broader than currently thought.Areas covered: The pharmacokinetics, pharmacodynamics, clinical efficacy, and safety profile of transdermal buprenorphine in moderate chronic noncancer pain syndromes patients will be discussed.Expert commentary: Buprenorphine offers effective analgesia in the form of a Schedule III drug (rather than Schedule II such as oxycodone or morphine) and transdermal buprenorphine is a convenient, accepted, around-the-clock pain reliever. Its lower potential for abuse should make it a more desirable pain reliever but many payers do not reimburse buprenorphine, driving prescribers and their patients to generic versions of the riskier Schedule II oral opioids such as oxycodone and morphine.

A Comparative Study of Transdermal Buprenorphine and Oral Morphine in the Treatment of Chronic Pain of Malignant Origin

Background and Objective:

The study was designed to compare the efficacy and adverse effects of buprenorphine transdermal (TD) against oral morphine in pain management of cancer patient.

Methods:

A randomized open-labeled prospective study was done in palliative cancer pain clinic in a tertiary care medical college between August 2017 and January 2018, to compare the efficacy (pain assessed by VAS) and adverse events (CTCAEv4) between arm A, buprenorphine TD, (20 μg/h, extended 7 days formulation) and arm B, oral morphine (10mg immediate releasing formulation). Patients with solid tumour malignancies with VAS score >40 (moderate to severe pain) were included in study.

Results:

63 patients were analyzed. Commonest primary cancers were breast in females and head and neck in male individuals in both arms. Initial VAS score of arm A and arm B were 81.25 and 82.26 respectively. By 1st week, 11 arm A patients were relieved from pain. Another 17 patients of arm A became pain free by 2nd week, total dose of 40 μg/h. Only 4 patients needed 60 μg/h for pain relief. In arm B, 2 patients were relieved by 1 week with total 30mg/day morphine, 11patients were relieved with 60 mg/day by 2nd week and 12 patients with 90 mg/day. 6 patients were relieved with 120 mg/day dose at the end of 4^th week. Nausea and constipation were stastically higher in Arm B compared to that of Arm-A.

Conclusions:

TD Buprenorphine had similar efficacy with oral morphine, with better toxicity profile and better compliance.

A physiologically based pharmacokinetic modelling approach to predict buprenorphine pharmacokinetics following intravenous and sublingual administration

AIMS

Opioid dependence is associated with high morbidity and mortality. Buprenorphine (BUP) is approved by the Food and Drug Administration to treat opioid dependence. There is a lack of clear consensus on the appropriate dosing of BUP due to interpatient physiological differences in absorption/disposition, subjective response assessment and other patient comorbidities. The objective of the present study was to build and validate robust physiologically based pharmacokinetic (PBPK) models for intravenous (IV) and sublingual (SL) BUP as a first step to optimizing BUP pharmacotherapy.

METHODS

BUP-PBPK modelling and simulations were performed using SimCyp® by incorporating the physiochemical properties of BUP, establishing intersystem extrapolation factors-based in vitro-in-vivo extrapolation (IVIVE) methods to extrapolate in vitro enzyme activity data, and using tissue-specific plasma partition coefficient estimations. Published data on IV and SL-BUP in opioid-dependent and non-opioid-dependent patients were used to build the models. Fourteen model-naïve BUP-PK datasets were used for inter- and intrastudy validations.

RESULTS

The IV and SL-BUP-PBPK models developed were robust in predicting the multicompartment disposition of BUP over a dosing range of 0.3-32 mg. Predicted plasma concentration-time profiles in virtual patients were consistent with reported data across five single-dose IV, five single-dose SL and four multiple dose SL studies. All PK parameter predictions were within 75-137% of the corresponding observed data. The model developed predicted the brain exposure of BUP to be about four times higher than that of BUP in plasma.

CONCLUSION

The validated PBPK models will be used in future studies to predict BUP plasma and brain concentrations based on the varying demographic, physiological and pathological characteristics of patients.

Presence or Absence of QTc Prolongation in Buprenorphine-Naloxone Among Youth With Opioid Dependence

OBJECTIVES

The aim of the study was to evaluate buprenorphine-naloxone effects on the QTc in youth with opioid dependence. Buprenorphine is a partial agonist that is an effective treatment for opioid dependence. Compared with methadone, it has a lower risk of QTc prolongation in adults, but is less studied in the youth. It may also reduce the risk of torsades de pointes (TdP)--an uncommon variant of polymorphic ventricular tachycardia--that can result in syncope, ventricular fibrillation, and sudden death.

METHODS

Secondary analysis of the electrocardiogram data from 95 individuals who participated in a multisite trial for youth with opioid dependence. The participants were randomized to a 2-week (DETOX) or a 12-week course of buprenorphine-naloxone (BUP). At baseline, 12-lead electrocardiograms were done at weeks 4 and 12, and QTc intervals were hand-measured and calculated using Bazett formula. Increases above 60 milliseconds were considered clinically significant, and readings above 450 milliseconds (in men) and 470 milliseconds (in women) indicated a prolonged QTc.

RESULTS

Mean QTc intervals were higher for BUP than for DETOX participants at baseline, week 4, and week 12 (P = 0.045), and women had longer mean QTc intervals than men (P < 0.0005). Variations in the QTc intervals were observed in some; however, none were above 500 milliseconds--the level at which risk for TdP becomes more significant.

CONCLUSIONS

In this randomized trial, the mean QTc at baseline, before randomization, was higher in BUP than in DETOX patients. Minimal changes in the QTc were seen at 4 and 12 weeks in a few patients in both groups. There was no evidence that buprenorphine-naloxone alone increased the QTc to a level that increased the risk for TdP.

Effect of buprenorphine as an adjunct with plain local anesthetic solution in supraclavicular brachial plexus block on quality and duration of postoperative analgesia

Background and Aims:

Supraclavicular brachial plexus block is ideal for upper limb surgical procedures. Buprenorphine, an agonist antagonist opioid has been used as an adjunct to prolong analgesia. We aimed to evaluate the quality and duration of postoperative analgesia by addition of buprenorphine to local anesthetic solution.

Material and Methods:

A prospective, randomized, double-blind control study was conducted on 50 healthy patients of ASA Grade I/II of age group 20-70 years scheduled for orthopedic and reconstructive surgery of upper limb under supraclavicular brachial plexus block. Patients were allocated into two groups, 25 in each group viz.: Group B (buprenorphine group) received 20 ml 0.5% bupivacaine + 15 ml 2% lignocaine with adrenaline (1:200,000) + 4 ml normal saline + 1500 units hyaluronidase + 3 μg/kg buprenorphine diluted to 1 ml normal saline. Group C (control group) received 20 ml 0.5% bupivacaine + 15 ml 2% lignocaine with adrenaline (1:200,000) + 4 ml normal saline + 1500 units hyaluronidase + 1 ml normal saline. The parameters observed were onset and duration of sensory and motor block, quality and duration of analgesia and side-effects.

Results:

The mean duration of postoperative analgesia was significantly longer in Group B (16.04 ± 3.19 h) than in Group C (6.20 ± 0.74 h). There was no difference between two groups on mean onset of sensory block. The mean duration motor block was significantly longer in Group B (4.93 ± 0.94 h) than in Group C (2.25 ± 0.62 h) [P < 0.05]. The mean duration of sensory block was also significantly longer in Group B (5.71 ± 0.94 h) than in Group C (4.94 ± 0.70 h) with P < 0.05.

Conclusion:

Addition of 3 μg/kg buprenorphine to 0.5% bupivacaine for supraclavicular brachial plexus block prolonged duration of postoperative analgesia and sensory blockade without an increase in side effects.

Operant nociception in nonhuman primates

The effective management of pain is a longstanding public health concern. Morphine-like opioids have long been front-line analgesics, but produce undesirable side effects that can limit their application. Slow progress in the introduction of novel improved medications for pain management over the last 5 decades has prompted a call for innovative translational research, including new preclinical assays. Most current in vivo procedures (eg, tail flick, hot plate, warm water tail withdrawal) assay the effects of nociceptive stimuli on simple spinal reflexes or unconditioned behavioral reactions. However, clinical treatment goals may include the restoration of previous behavioral activities, which can be limited by medication-related side effects that are not measured in such procedures. The present studies describe an apparatus and procedure to study the disruptive effects of nociceptive stimuli on voluntary behavior in nonhuman primates, and the ability of drugs to restore such behavior through their analgesic actions. Squirrel monkeys were trained to pull a cylindrical thermode for access to a highly palatable food. Next, sessions were conducted in which the temperature of the thermode was increased stepwise until responding stopped, permitting the determination of stable nociceptive thresholds. Tests revealed that several opioid analgesics, but not d-amphetamine or Δ(9)-THC, produced dose-related increases in threshold that were antagonist sensitive and efficacy dependent, consistent with their effects using traditional measures of antinociception. Unlike traditional reflex-based measures, however, the results also permitted the concurrent evaluation of response disruption, providing an index with which to characterize the behavioral selectivity of antinociceptive drugs.

Mixed κ/μ partial opioid agonists as potential treatments for cocaine dependence

Cocaine use activates the dopamine reward pathway, leading to the reinforcing effects of dopamine. There is no FDA-approved medication for treating cocaine dependence. Opioid agonists and antagonists have been approved for treating opioid and alcohol dependence. Agonists that activate the μ opioid receptor increase dopamine levels in the nucleus accumbens, while μ receptor antagonists decrease dopamine levels by blocking the effects of endogenous opioid peptides. Activation of the κ opioid receptor decreases dopamine levels and leads to dysphoria. In contrast, inhibition of the κ opioid receptor decreases dopamine levels in the nucleus accumbens. Antagonists acting at the κ receptor reduce stress-mediated behaviors and anxiety. Mixed partial μ/κ agonists have the potential of striking a balance between dopamine levels and attenuating relapse to cocaine. The pharmacological properties of mixed μ/κ opioid receptor agonists will be discussed and results from clinical and preclinical studies will be presented. Results from studies with some of the classical benzomorphans and morphinans will be presented as they lay the foundation for structure-activity relationships. Recent results with other partial opioid agonists, including buprenorphine derivatives and the mixed μ/κ peptide CJ-15,208, will be discussed. The behavioral effects of the mixed μ/κ MCL-741, an aminothiazolomorphinan, in attenuating cocaine-induced locomotor activity will be presented. While not a mixed μ/κ opioid, results obtained with GSK1521498, a μ receptor inverse agonist, will be discussed. Preclinical strategies and successes will lay the groundwork for the further development of mixed μ/κ opioid receptor agonists to treat cocaine dependence.

Perinatal outcomes of Australian buprenorphine-exposed mothers and their newborn infants

AIM

To determine the short-term outcomes of Australian buprenorphine-exposed mother/infant dyads.

METHODS

Retrospective record review of drug-exposed mothers and infants in Australia. Groups were based on drug exposure: buprenorphine (55, 3.8%), non-buprenorphine opiates (O, 686, 48.6%) and non-opiates (NO, 671, 47.5%).

RESULTS

More than 30% of buprenorphine mothers continued to use heroin (21, 38%) and benzodiazepines (16, 29%). They were more likely to have child at risk concerns (29, 52.7%, P = 0.019) and have previous children placed in out-of-home care (9, 16.3%, P = 049). Buprenorphine babies were less likely to be preterm (16% vs. 25% (O), P = 0.001 and 23% (NO), P = 0.004) and had higher birthweights (median: 3165 g vs. 2842.5 g (O), P < 0.001 and 2900 g (NO), P = 0.004). Buprenorphine and non-buprenorphine opioid babies had similar maximum Finnegan scores (median 10 vs. 11(O), P = 0.144). The number of babies needing abstinence treatment (45% vs. 51% (O), P = 0.411) and length of hospital stay (median days 9 vs. 11(O), P = 0.067) were similar, but buprenorphine infants required lower maximum morphine doses (mg/kg/day) (median 0.4 mg vs. 0.5 mg (O), P = 0.009).

CONCLUSIONS

Short-term medical outcomes of infants of buprenorphine-using mothers are similar to those of non-buprenorphine opiate-using mothers, but interpretation of these results is confounded by the high rates of polydrug exposure in the buprenorphine group. This and other social concerns noted in buprenorphine mothers and infants warrant further study.

Effect of fentanyl versus buprenorphine on the pupil size in phacoemulsification cataract surgery

BACKGROUND

Despite several recent innovations in phacoemulsification surgery, importance of pupil diameter in this surgery is becoming more evident.

PURPOSE

To compare the effect of opioid agonist (fentanyl) versus opioid agonist-antagonist (buprenorphine) on pupil diameter in cataract surgery and to choose the best opioid in high-risk phacoemulsification surgery.

METHODS

In this randomized double-blinded clinical trial, 60 patients who were candidates for elective phacoemulsification surgery were randomly divided into two equal groups: experimental (buprenorphine, 0.3 μg/kg) and control (fentanyl, 1 μg/kg). Pupil diameter was measured preinjection and at several times postinjection. Blood pressure was recorded at several intervals, as well as shivering, nausea and vomiting, and recovery time.

RESULTS

Mean (SD) recovery time was significantly less in the control group (19.46±5.43) than in the experimental group (33.23±10.75) (P<0.0001). The constriction effect (ie, pupillary diameter in mm) was significantly lower in the experimental group (0.53±0.45) than in the control group (1.06±0.52) (P=0.0001). The percentages of constriction effect in experimentaland control groups were 7.68% and 15.07%, respectively. The eye was two times more constricted in the control group in comparison with the experimental group after induction of anesthesia.

CONCLUSION

Buprenorphine is a better solution to decrease pupil constriction in comparison with fentanylinhigh-risk phacoemulsification surgery.

Buprenorphine with bupivacaine for intraoral nerve blocks to provide postoperative analgesia in outpatients after minor oral surgery

PURPOSE

The demonstration that opioid receptors exist in the peripheral nervous system offers the possibility of providing postoperative analgesia in the ambulatory surgical patient. Over the previous decade, many investigators have studied this approach and have compared the efficacy of various opioids added to the local anesthetic near the brachial plexus; and it appears from several of these studies that buprenorphine provides the longest duration of analgesia, the most important parameter of postoperative analgesia in outpatients. One of these studies indicated that the agonist-antagonist, buprenorphine, added to bupivacaine provided a longer period of postoperative analgesia than the traditional opiates, but none of the studies was performed in patients undergoing minor oral surgery to check the efficacy of buprenorphine to provide postoperative analgesia in dental patients. The present study was undertaken to ascertain the efficacy of buprenorphine in providing prolonged postoperative analgesia when added to 0.5% bupivacaine with epinephrine 1:200,000.

PATIENTS AND METHODS

Fifty healthy, consenting adult patients scheduled for upper extremity surgery were enrolled in the study. Patients were assigned randomly to 1 of 2 equal groups based on the agents used for the blocks. Patients in group I received 40 mL of a local anesthetic alone, and those in group II received the same local anesthetic plus buprenorphine 0.3 mg. The study was kept double-blind by having one dentist prepare the solutions, a second dentist perform the blocks, and a third dentist monitor the anesthesia and analgesia thereafter, up to and including the time of the first request for an analgesic medication. The data were reported as means +/- standard errors of the mean, and differences between groups were determined using t test. A P value less than .01 was considered statistically significant.

RESULTS

The mean duration of postoperative pain relief after injection of the local anesthetic alone was 8.34 +/- 0.11 hours compared with 28.18 +/- 1.02 hours after buprenorphine was added, a difference that was statistically (and clinically) significant (P < .001).

CONCLUSION

The addition of buprenorphine to the local anesthetic used for intraoral nerve blocks in the present study provided a 3-fold increase in the duration of postoperative analgesia, with complete analgesia persisting 30 hours beyond the duration provided by the local anesthetic alone in 75% of patients. This practice can be of particular benefit to patients undergoing minor oral surgery by providing prolonged analgesia after discharge from the hospital.

P-glycoprotein mediates brain-to-blood efflux transport of buprenorphine across the blood–brain barrier

The involvement of P-glycoprotein (P-gp) in buprenorphine (BNP) transport at the blood-brain barrier (BBB) in rats was investigated in vivo by means of both the brain uptake index technique and the brain efflux index technique. P-gp inhibitors, such as cyclosporin A, quinidine and verapamil, enhanced the apparent brain uptake of [3H]BNP by 1.5-fold. The increment of the BNP uptake by the brain suggests the involvement of a P-gp efflux mechanism of BNP transport at the BBB. [3H]BNP was eliminated with an apparent elimination half-life of 27.5 min after microinjection into the parietal cortex area 2 regions of the rat brain. The apparent efflux clearance of [3H]BNP across the BBB was 0.154 ml/min/g brain, which was calculated from the elimination rate constant (2.52 x 10- 2 min- 1) and the distribution volume in the brain (6.11 ml/g brain). The efflux transport of [3H]BNP was inhibited by range from 32 to 64% in the presence of P-gp inhibitors. The present results suggest that BNP is transported from the brain across the BBB via a P-gp-mediated efflux transport system, at least in part.

Effects of buprenorphine on body temperature, locomotor activity and cardiovascular function when assessed by telemetric monitoring in rats

Buprenorphine is a potent analgesic commonly used clinically in humans and rodents experiencing severe pain. However, effects of therapeutic doses on locomotor activity and the cardiovascular system have not been studied in conscious animals. The effects of buprenorphine were therefore evaluated in this study using telemetric monitoring in conscious animals. Telemetry transmitters were implanted in the peritoneal cavity of Wistar rats with a pressure catheter in the aorta and electrodes for electrocardiogram (ECG) recording subcutaneously. After a single subcutaneous administration of saline, each rat was administered single subcutaneous doses of 0.006, 0.03 or 0.15 mg/kg body weight (bw) of buprenorphine. During a 10 h period after administration, buprenorphine induced a varying dose-dependent increase in body temperature, heart rate, dP/dt and systolic-diastolic blood pressure, as well as a corresponding decrease in QT time. At high dose, however, QT time was still decreased 24 h post-administration, but no arrhythmias or visual changes were observed in the ECG complex. Body temperature and heart rate increased at the high dose of buprenorphine, even at 20-24 h after administration. Moreover, the high dose of buprenorphine induced a biphasic response in diastolic blood pressure, with an early and pronounced increase that, at 14 h after administration, reversed to a decrease, failing to normalize within 24 h post-dosage. The results indicate that buprenorphine induces long-lasting effects (such as body temperature and cardiovascular effects) in the rat after a single subcutaneous dose at 0.15 mg/kg bw.

Buprenorphine: considerations for pain management

New effective analgesics are needed for the treatment of pain. Buprenorphine, a partial mu-opioid agonist which has been in clinical use for over 25 years, has been found to be amenable to new formulation technology based on its physiochemical and pharmacological profile. Buprenorphine is marketed as parenteral, sublingual, and transdermal formulations. Unlike full mu-opioid agonists, at higher doses, buprenorphine's physiological and subjective effects, including euphoria, reach a plateau. This ceiling may limit the abuse potential and may result in a wider safety margin. Buprenorphine has been used for the treatment of acute and chronic pain, as a supplement to anesthesia, and for behavioral and psychiatric disorders including treatment for opioid addiction. Prolonged use of buprenorphine can result in physical dependence. However, withdrawal symptoms appear to be mild to moderate in intensity compared with those of full mu agonists. Overdoses have primarily involved buprenorphine taken in combination with other central nervous system depressants.

Buprenorphine added to the local anesthetic for brachial plexus block to provide postoperative analgesia in outpatients

BACKGROUND AND OBJECTIVES

Over the past 10 years, several studies have suggested that the addition of certain opiates to the local anesthetic used for brachial block may provide effective, long-lasting postoperative analgesia. One of these studies indicated that the agonist-antagonist, buprenorphine, added to bupivacaine provided a longer period of postoperative analgesia than the traditional opiates, but in this study, it is impossible to determine the relative contributions of the local anesthetic and the opiate to the postoperative analgesia because of the extremely long duration of the anesthesia provided by the local anesthetic, bupivacaine. By repeating the study using a local anesthetic of a shorter duration, the present study delineates more clearly the contribution of the buprenorphine to postoperative analgesia when added to a shorter-acting local anesthetic.

METHODS

Forty, healthy, consenting adult patients scheduled for upper extremity surgery were enrolled in the study. Premedication was provided by intravenous midazolam 2 mg/70 kg and anesthesia by a subclavian perivascular brachial plexus block. The patients were assigned randomly to 1 of 2 equal groups based on the agents used for the blocks. The patients in group I received 40 mL of a local anesthetic alone, while those in group II received the same local anesthetic plus buprenorphine 0.3 mg. The study was kept double-blind by having 1 anesthesiologist prepare the solutions, a second anesthesiologist perform the blocks, and a third anesthesiologist monitor the anesthesia and analgesia thereafter, up to and including the time of the first request for an analgesic medication. The data were reported as means (+/- SEM), and differences between groups were determined using repeated measures of analysis of variance (ANOVA) and chi(2), followed by the Fisher exact test for post hoc comparison. A P value of less than.05 was considered to be statistically significant.

RESULTS

The mean duration of postoperative pain relief following the injection of the local anesthetic alone was 5.3 (+/- 0.15) hours as compared with 17.4 (+/- 1.26) hours when buprenorphine was added, a difference that was statistically (and clinically) significant (P <.0001).

CONCLUSIONS

The addition of buprenorphine to the local anesthetic used for brachial plexus block in the present study provided a 3-fold increase in the duration of postoperative analgesia, with complete analgesia persisting 30 hours beyond the duration provided by the local anesthetic alone in 75% of the patients. This practice can be of particular benefit to patients undergoing ambulatory upper extremity surgery by providing prolonged analgesia after discharge from the hospital.

Postoperative pain control following remifentanil-based anaesthesia for major abdominal surgery

Eighty patients undergoing major abdominal surgery using remifentanil-based anaesthesia were randomly allocated in a double-blind manner to receive an intravenous bolus of fentanyl, buprenorphine, morphine or piritramide 20 min before the end of surgery. A reduced dose was administered postoperatively when patients reported moderate pain. Subsequent analgesia was provided by patient-controlled analgesia (PCA). The mean time from the end of anaesthesia to spontaneous respiration was 9 +/- 5 min. At first pain assessment, 63% of patients reported no or mild pain; 80% of patients required the second opioid bolus, those receiving piritramide needed the bolus significantly later than patients receiving buprenorphine or fentanyl. First PCA requirement also occurred significantly later in the piritramide group. This technique provided effective postoperative pain relief and transition to routine PCA and did not compromise recovery.

Antinociceptive effect induced by the combined administration of spinal morphine and systemic buprenorphine

We evaluated the antinociceptive effect of combined spinal administration of morphine and systemic administration of buprenorphine. Experiments were performed on male Wistar rats. Nociception was measured using the tail immersion test. Buprenorphine was injected intraperitoneally (IP) and morphine was injected intrathecally (IT) via a catheter implanted in the subarachnoid space. Interaction of drugs was analyzed using a dose addition model. Both IT (1-5 microg) morphine and IP (50-500 microg/kg) buprenorphine increased the latencies of nociceptive responses in a dose-dependent manner. IT morphine (4 microg) and IP buprenorphine (100 microg/kg) produced 62.9+/-6.3 and 48.8+/-6.6 percent of the maximal possible effect (%MPE), respectively. The combined administration of 2 microg of IT morphine and 50 microg/kg IP buprenorphine produced a %MPE of 97.1+/-3.4. The analysis of drug interaction revealed that IT morphine interacted with IP buprenorphine in a supraadditive manner while producing a potent antinociceptive effect.

IMPLICATIONS

The concurrent administration of spinal morphine and systemic buprenorphine produces an antinociceptive effect that is greater than what could have been predicted from individual dose-response curves. This mode of interaction allows maintenance at a significant level of analgesia with reduced doses of opioids, which minimizes the incidence of undesirable side effects.

[Effectiveness and tolerance of tramadol in cancer pain. A comparative study with respect to buprenorphine]

Opioid analgesics represent one of the most important tools in a sequential pharmacological approach to oncological pain relief. They are recommended by the WHO when nonsteroidal anti-inflammatory drugs (NSAIDs) no longer provide adequate analgesia. However, the use of opioids is limited because of their numerous and often severe adverse effects. This aspect of opioids has motivated continuous research projects aimed at discovering drugs that can provide maximum pain relief but with improved tolerability. Tramadol is a new, centrally acting analgesic with a dual mechanism of action. It shows a selective interaction with mu receptors, which are responsible for nociception, and has weak pharmacodynamic activity on other opioid receptors. At the same time, it acts synergistically on neuroamine transmission by inhibiting synaptic noradrenaline (norepinephrine) reuptake and inducing intrasynaptic serotonin (5-hydroxytryptamine; 5-HT) release. From a pharmacokinetic standpoint, tramadol offers high bioavailability, with similar patterns after oral or parenteral administration (half-life 5 to 7 hours, time to peak plasma concentration 3.1 hours, and approximately 20% plasma protein binding). Although the efficacy of tramadol is comparable to that of other drugs with similar modes of action, the incidence of side effects such as constipation and respiratory depression is lower. The frequency of euphoria and dysphoria is negligible, resulting in little risk of abuse or dependence. It therefore seemed appropriate to further investigate the efficacy and tolerability of tramadol, defined as having only weak potency, in comparison with a widely used opioid, in oncological pain. Buprenorphine was selected as an opioid with a potency equivalent to half that of morphine, but with tolerability that is partially limited by the fact that it frequently gives rise to adverse reactions considered typical of stronger opioids. To compare the analgesic effect and tolerability of tramadol and buprenorphine, 60 patients (44 men, 16 women; average age 61.4 years), all presenting with advanced tumours, were treated orally in a controlled crossover trial with randomised sequences. Patients took both drugs, each for a week, with a 24-hour washout period between treatments. Tramadol was prescribed at the daily dose of 300mg, orally, and buprenorphine at 0.6 mg/day, as a sublingual preparation. Assessments were made of Karnofsky performance status and severity of pain before and during the 4 hours after taking the 2 drugs. Each patient also completed a daily diary recording the severity of pain 1 hour after the dose, the evolution of pain during the day and its severity compared with that on the previous day. They also assessed the duration and quality of sleep. The Karnofsky index changed little with either treatment, but all other variables showed worthwhile improvement, indicating the significant analgesic effect of both drugs. Buprenorphine and tramadol had a similar analgesic effect, although the improvement with the test drug was significant within 1 hour of administration (p < 0.05 compared with baseline) and more marked (p < 0.05 on day 2 compared with buprenorpine). At the end of tramadol treatment, sleep had also improved, both quantitatively and qualitatively (both p < 0.05). The final assessment was significantly in favour of tramadol as regards efficacy (p < 0.05) and patient acceptability (p < 0.01). Thus, tramadol was better tolerated than buprenorphine, and caused fewer and milder adverse reactions. Only 1 patient discontinued tramadol, compared with 18 using reference therapy. Tramadol, although theoretically less potent, nevertheless brought about as much pain relief as the comparator opioid. In conclusion, for this class of drug, tramadol provides an excellent balance between efficacy and tolerability, confirming preliminary studies.

Noncardiogenic pulmonary edema induced by sublingual buprenorphine

A 21-year-old woman developed noncardiogenic pulmonary edema within 90 min after the use of buprenorphine, 0.2 mg, sublingually for severe dysmenorrhea. No organic cardiovascular illness was detected. The pulmonary edema resolved spontaneously with conservative treatment. The mechanism of pulmonary edema may be an allergic reaction to buprenorphine.

Transdermal delivery of buprenorphine through cadaver skin

The skin permeation of buprenorphine base and HCl salt through cadaver skin was investigated. The octanol-water partition coefficient and solubilities of both buprenorphine free base and HCl salt were determined at 32 degrees C. As expected, buprenorphine free base was more lipophilic than its HCl salt and was practically insoluble in aqueous buffer at pH 8.7. The drug solubility decreased exponentially as the pH of the solution increased, whereas the permeability coefficient increased as the donor solution pH decreased. The skin flux of buprenorphine.HCl was significantly higher than that of the free base from propylene glycol/lauric acid vehicle mixtures. Buprenorphine base permeation through tape-stripped epidermis suggested that in addition to stratum corneum, viable epidermis presented a significant diffusion barrier because of the very low aqueous solubility of the free base observed. The mean steady-state skin fluxes of buprenorphine.HCl were 20.3 and 29.7 micrograms/cm2/h from propylene glycol:lauryl alcohol: ethanol (80:15:5) and propylene glycol: propylene glycol monolaurate: water (80:15:5) vehicle mixtures, respectively. The skin flux of buprenorphine.HCl from various monolithic matrix patches was also evaluated. When capric acid, lauric acid, and lauryl alcohol were separately incorporated into an adhesive matrix, the skin flux of buprenorphine.HCl was enhanced by a factor of 2 to 3.5. Finally, based on the total body clearance and minimum effective concentration of buprenorphine, a transdermal delivery rate of 2.5 micrograms/cm2/h from a 20-cm2 patch was estimated. The in vitro skin permeation data clearly suggest that transdermal delivery of buprenorphine is feasible to achieve a desired systemic analgesic effect.

[Risk evaluation of oxygen desaturation after buprenorphine or morphine administration during the early postoperative period]

The purpose of this study, conducted in a PACU in the early recovery period of orthopaedic procedures under general anaesthesia, was to compare the time course of O2 arterial saturation (SpO2), measured by pulse oximetry, after the intramuscular administration of either buprenorphine (0.30 mg) or morphine (10 mg). The rate of patients who had an episode of O2 desaturation (defined as a SpO2 under 95%) was similar in both groups: 73% after buprenorphine vs 67% after morphine. The cumulative duration of desaturation episodes was higher following buprenorphine (p < 10(-5). Finally, in patients who had at least one episode of arterial desaturation, the mean duration of these episodes was identical in both groups. However the average number of episodes per patient was significantly higher in the buprenorphine group. These results should lead us to be cautious with the use of buprenorphine during the early recovery period, especially as this as this agent has specific characteristics such as a long duration of action and resistance to naloxone.

Comparison of the ventilatory effects of morphine and buprenorphine in children

This study was a prospective, randomized comparison of the ventilatory effects of equianalgesic single-doses of morphine, 100 micrograms/kg, and buprenorphine, 3.0 micrograms/kg, administered intravenously to 20 children (5-8 years of age) after elective ophthalmic surgery. The decrease in ventilatory rate and acute change in the arteriolar oxygen saturation and the increase in end-tidal CO2 levels were statistically significantly greater in magnitude and duration after buprenorphine than after morphine. For both drugs, the time, duration and magnitude of ventilatory changes varied appreciably between individuals. No child had apnea or hypoventilation requiring assistance. The authors conclude that acutely administered buprenorphine depresses ventilation to a greater degree than morphine. The maximal ventilatory effect of buprenorphine occurs later than with morphine, and ventilatory depression after buprenorphine may develop late. For safety, all children given opioids intravenously should be observed until they are fully responsive and ventilatory control has stabilized.

Complications related to thoracic epidural analgesia: a prospective study in 1071 surgical patients

In a prospective study, the complications of 1071 patients scheduled for thoracic epidural catheterization for postoperative analgesia (TEA) were studied. All catheters were inserted preoperatively between segment Th 2/3 and Th 11/12 under local anesthesia. Balanced anesthesia with endotracheal intubation and TEA were combined. Postoperatively 389 patients (36.9%) were monitored on a normal surgical ward. Buprenorphine, 0.15 to 0.3 mg, and if needed bupivacaine 0.375% 3-5 ml h-1 were given epidurally. Primary perforation of the dura occurred in 13 patients (1.23%). Radicular pain syndromes were observed in six patients (0.56%). In one patient (0.09%) respiratory depression was seen in close connection with the epidural administration of 0.3 mg buprenorphine. Although 116 patients (10.83%) showed one abnormal clotting parameter but no clinical signs of hemorrhage, there was no complication related to this group. No persisting neurological sequelae caused by the thoracic epidural catheters were found. In conclusion, continuous TEA with buprenorphine for postoperative pain relief after major abdominal surgery is a safe method without too high a risk of catheter-related or drug-induced complications, even on a normal surgical ward and when one clotting parameter is abnormal.

Failure of transcutaneous electrical nerve stimulation and indomethacin to reduce opiate requirement following cholecystectomy

This randomized study examined the effect of transcutaneous electrical nerve stimulation (TENS) and indomethacin on postoperative opiate requirement in 60 patients after cholecystectomy. An open intravenous bolus of 25 mg of indomethacin followed by an infusion of 5 mg in 1 h, alone or combined with either low or high frequency TENS, was administered during the study period of 16 h. An intravenous bolus of either 5 mg of oxycodone or 0.15 mg of buprenorphine was administered double blindly for postoperative pain relief. The number of doses of buprenorphine given (3, 9) differed (P = 0.01) from the number of doses of oxycodone given (5, 4). Neither indomethacin nor TENS reduced the postoperative opiate requirement.

Opioid agonist-antagonist drugs in acute and chronic pain states

The agonist-antagonist opioid analgesics are a heterogeneous group of drugs with moderate to strong analgesic activity comparable to that of the pure agonist opioids such as codeine and morphine but with a limited effective dose range. The group includes drugs which act as an agonist or partial agonist at one receptor and an antagonist at another (pentazocine, butorphanol, nalbuphine, dezocine) and drugs acting as a partial agonist at a single receptor (buprenorphine). These drugs can be classified as nalorphine-like or morphine-like. Meptazinol does not fit into either classification and occupies a separate category. Pentazocine, butorphanol and nalbuphine are weak mu-antagonists and kappa-partial-agonists. All three drugs are strong analgesics when given by injection: pentazocine is one-sixth to one-third as potent as morphine, nalbuphine is slightly less potent than morphine, and butorphanol is 3.5 to 7 times as potent. The duration of analgesia is similar to that of morphine (3 to 4 hours). Oral pentazocine is closer in analgesic efficacy to aspirin and paracetamol (acetaminophen) than the weak opioid analgesics such as codeine. Neither nalbuphine nor butorphanol is available as an oral formulation. At usual therapeutic doses nalbuphine and butorphanol have respiratory depressant effects equivalent to that of morphine (though the duration of such effects with butorphanol may be longer). Unlike morphine there appears to be a ceiling to both the respiratory depression and the analgesic action. All of these 3 drugs have a lower abuse potential than the pure agonist opioid analgesics such as morphine. However, all have been subject to abuse and misuse, and pentazocine (but not the others) is subject to Controlled Drug restrictions. Buprenorphine is a potent partial agonist at the mu-receptor, and by intramuscular injection is 30 times as potent as morphine. A ceiling to the analgesic effect of buprenorphine has been demonstrated in animals and it is also claimed in humans. However, there are no reliable data available to define the maximal dose of buprenorphine in humans. A practical ceiling exists for sublingual use in that the only available formulation is a 2 micrograms tablet and few patients will accept more than 3 or 4 of these in a single dose. The duration of analgesia is longer than that of morphine, at 6 to 9 hours. There have been suggestions that buprenorphine causes less respiratory depression than morphine, but viewed overall it appears that in equianalgesic doses the 2 drugs have similar respiratory depressant effects.(ABSTRACT TRUNCATED AT 400 WORDS)

Variations in hemodynamic and stress hormonal responses in open heart surgery with buprenorphine/diazepam anesthesia

The use of buprenorphine-diazepam-N2O (60%)-O2 anesthesia in open heart surgery was investigated. The authors examined the hemodynamic changes produced and the response of stress hormones. Twenty adult patients with atrial septal defects undergoing surgical correction were studied in two groups of 10, receiving either 6 micrograms/kg of buprenorphine (B6) or 12 micrograms/kg of buprenorphine (B12) for the induction of anesthesia. Both groups received a subsequent dose of 6 micrograms/kg of buprenorphine with the commencement of extracorporeal circulation (ECC). With surgery, mean arterial pressure showed a transient increase in both groups and thereafter was stable. Heart rate in the B6 group was increased from the onset of surgery to the day after, while the B12 group showed no significant change. Filling pressures showed no change in either group. Plasma catecholamine concentrations in the B6 group, in contrast to the B12 group, increased significantly from midoperation to after completion of the operation (ECC 10 minutes, B6 group v B12 group: plasma norepinephrine 616 +/- 231 v 195 +/- 38 pg/mL, plasma epinephrine 1385 +/- 392 v 572 +/- 132 pg/mL, P less than 0.05). Plasma ADH levels in both groups rose with the commencement of surgery, reaching a peak at ECC 10 minutes (B6 group 88.1 +/- 8.4 v B12 group 124.4 +/- 27.2 pg/mL). However, in contrast to plasma catecholamines, the antidiuretic hormone (ADH) levels in the B12 group remained higher until the first postoperative day. Therefore, patients who received the larger dose of buprenorphine had better control of hemodynamics and catecholamines, but a greater elevation of plasma ADH levels.

Effect of buprenorphine on the cardiovascular response to tracheal intubation

The effects of buprenorphine on the haemodynamic responses to tracheal intubation were studied in a placebo-controlled double-blind trial in 40 patients who had elective surgery. In one group saline was administered intravenously 8 minutes before induction, whereas the others received buprenorphine 2.5 micrograms/kg intravenously. Anaesthesia was induced in both groups with thiopentone 4 mg/kg followed by suxamethonium 1.5 mg/kg after 90 seconds. In the buprenorphine group, the maximum increase in systolic and diastolic arterial blood pressures, heart rate and rate pressure product were significantly lower compared to the control group. It is concluded that buprenorphine is partially effective in attenuating the cardiovascular response to laryngoscopy and intubation, but does not obliterate it.

Effects of buprenorphine on motor activity of the sphincter of Oddi in man

Buprenorphine, (Temgesic), a N-cyclopropylmethyl derivative of oripavine, is both an agonist and antagonist of morphine. Its effect on the motility of the sphincter of Oddi (SO) in humans have been investigated by endoscopic manometry (EM). Buprenorphine leads to a significant decrease in the amplitude of SO contraction waves without altering other parameters. Thus, it has no morphine-like effect on SO motility, but it does act like a partial antagonist of morphine in reducing the amplitude of SO contraction waves.

Postoperative paraplegia associated with epidural narcotic administration

Epidural injections of buprenorphine were given for postoperative pain relief to a patient with pulmonary carcinoma who underwent a right upper lobectomy. Paraplegia occurred postoperatively and the patient's neurological status deteriorated after each injection of epidural narcotic. Laminectomies on the third postoperative day revealed an expanded oxidized cellulose (Oxycel) pledget in the epidural space. Neurologic dysfunction after epidural narcotic administration was caused by the oxidized cellulose which had migrated into the epidural space following use for surgical haemostasis and subsequently expanded with the narcotic solution and blood.

Crossover trials in clinical analgesic assays: studies of buprenorphine and morphine

Analgesic studies of buprenorphine, a thebaine derivative and potent partial narcotic agonist, were carried out in patients with cancer who had postoperative or chronic pain. Intramuscular buprenorphine was compared with intramuscular morphine in a series of sequentially related, twin crossover assays and was found to be about 25 times as potent as morphine. Side effects were essentially morphine-like. In a second assay, the acceptability and analgesic activity of sublingual buprenorphine was studied in a 6-dose, balanced, incomplete block assay, a modification of the twin crossover design employed in the all-intramuscular trial. Sublingual buprenorphine was found to be about 15 times as potent as intramuscular morphine and was well accepted by our patients. The 4-dose twin crossover trial in which doses are adjusted sequentially is more flexible in that a wide range of doses may be studied, but it lacks the ability of the 6-dose design to provide estimates of the curvature of the dose-response slopes of the study drugs. When first-dose-only data were analyzed as parallel group assays, the main difference in results compared with the crossover studies was a decrease in efficiency and sensitivity.

A combination of buprenorphine and naloxone compared with buprenorphine administered intramuscularly in postoperative patients

Sixty patients suffering from moderate to severe pain following either orthopaedic or gynaecological surgery were treated with intramuscular buprenorphine (0.3 mg) or an intramuscular combination of buprenorphine (0.3 mg)/naloxone (0.2 mg) and the analgesic efficacy and safety of the two treatments was compared. The evaluation of efficacy showed that both treatments provided good analgesia which was apparent at the first assessment time (10 minutes) and continued for approximately 10 hours. Only seven patients suffered from unwanted side-effects with only drowsiness/sleepiness and nausea being reported by more than one patient. Over-all analysis of the results showed that there were no significant differences between the two treatments with regard to efficacy and safety.

Comparison of intramuscular buprenorphine and a buprenorphine/naloxone combination in the treatment of post-operative pain

The analgesic efficacy and tolerance of a single intramuscular injection of either buprenorphine (0.3 mg) or a buprenorphine (0.3 mg)/naloxone (0.2 mg) combination was compared in 70 patients suffering from moderate to severe pain after abdominal surgery. Patients in both treatment groups experienced good analgesia which was apparent within 10 minutes of administration and lasted for approximately 12 hours. The most frequently reported unwanted effects were drowsiness and/or sleepiness and nausea and/or vomiting which were of mild or moderate severity in most cases. No significant differences were seen between the two treatment groups with regard to the overall assessments of efficacy and tolerance.

Longterm treatment with epidural opioids. A retrospective study comprising 150 patients treated with morphine chloride and buprenorphine

During a 2-year period, 150 patients were treated with epidural opioids for more than 7 days; 89 received morphine and 61 buprenorphine. In 16 cases, medication was changed from morphine to buprenorphine, and in 6 from buprenorphine to morphine. In 19 patients in each group, the disease process was benign. The median daily dose of morphine was 17 mg given by an average of 2.9 injections; the corresponding figures in the buprenorphine group were 1.3 mg and 2.6 injections. The mean duration of treatment was 49 days (7-397) in the morphine group and 53 days (7-262) in the buprenorphine group. Satisfactory pain relief was achieved in 40 (45%) patients who received morphine and 41 (67%) patients given buprenorphine. Altering medication from morphine to buprenorphine improved analgesia in 32% of patients, while the reverse improved pain relief in a further 46% of the patients. Side effects were reported in 46% of patients given morphine and 20% given buprenorphine. Seventy-one patients were treated on an outpatient basis. In these cases, buprenorphine was administered for 89% of the total duration of treatment and morphine chloride for 52%.

Buprenorphine delays drug absorption and gastric emptying in man

The aim of the present study was to investigate the effects of buprenorphine on drug absorption and gastric emptying in man, using paracetamol absorption as an index of gastric emptying rate. Paracetamol was given to eight healthy volunteers p.o. together with or without a single i.v. dose of buprenorphine 4 micrograms kg-1 body weight. Nausea occurred in five of the subjects, four subjects vomited and one was excluded due to vomiting during the study period. The mean peak serum paracetamol concentration (Cmax) was significantly (P less than 0.0002) lowered by a factor 3 by buprenorphine, the mean time from administration of paracetamol to its peak concentration (Tmax) was significantly (P less than 0.03) prolonged by a factor 6, and the area under the plasma concentration-time curve from 0 to 120 min was significantly (P less than 0.00006) reduced by a factor 3. This demonstrates a marked inhibition of the rate of paracetamol absorption, indicating a clinically important reduction of gastric emptying following administration of buprenorphine.

Postoperative pain relief with naloxone. Severe respiratory depression and pain after high dose buprenorphine

Buprenorphine 30 and 40 micrograms/kg was given as the sole intravenous analgesic in balanced anaesthesia to 12 patients undergoing cholecystectomy. Significant and severe respiratory depression was found 15 minutes after preoperative loading with buprenorphine. In the immediate postoperative period six patients were in pain. They were treated with naloxone 0.08-0.4 mg leading to a long lasting period of pain relief (median 22 hours).

Regular interval preventive pain relief compared with on demand treatment after hysterectomy

Eighty otherwise healthy women, aged 22-64 years, admitted for elective hysterectomy were studied in a prospective randomized trial. The aim was to compare two different postoperative pain relief schedules--one with the analgesic given at regular intervals and the other with the analgesic given on demand. All the patients had a neuroleptanaesthesia with fentanyl. Forty patients received an initial dose of buprenorphine 0.3 mg intravenously before termination of anaesthesia and continued with sublingual buprenorphine 0.4 mg 6 hourly postoperatively (regular interval (RI) group). Forty patients received the standard postoperative medication, meperidine 1 mg/kg on demand in the recovery room, followed by ketobemidone 5 mg subcutaneously on demand in the surgical ward (on demand (OD) group). There was no difference between groups concerning pain relief following a single dose of analgesic (P greater than 0.05, type II error 1-5%). In the recovery room 17.5% of the patients in the RI group received an analgesic compared to 87.5% in the OD group (P less than 0.05). Among patients in the RI group who had previously got injections for postoperative pain relief on demand 95% preferred regular interval sublingual buprenorphine for future treatment. The nurses found that 90% of the patients in the RI group were treated adequately compared to 62.5% of the patients in the OD group (P less than 0.05). It is concluded, that regular interval preventive pain relief is superior to conventional on demand analgesic therapy in postoperative pain.

Sublingual buprenorphine for premedication and postoperative pain relief in orthopaedic surgery

The effect of sublingual buprenorphine (Temgesic) as a premedicant and for postoperative pain relief compared with morphine/pethidine was studied in 50 patients scheduled for elective surgery of the knee joint. Twenty-five patients received buprenorphine 0.4 mg sublingually 1 h before surgery and the same dose on demand postoperatively. Twenty-five patients were given morphine intramuscularly (7.5 mg or 10 mg to females and males respectively) 1 h preoperatively. This group received pethidine (75 mg) intramuscularly on demand postoperatively. All the patients were anaesthetized with halothane N2O/O2 after induction with thiopentone. No significant differences were found with regard to sedation, dizziness, nausea and vomiting during the study period. Emergence shivering, confusion and restlessness just after termination of the operation were equal in the two groups. In the recovery room, however, there was a higher frequency of shivering (P less than 0.05) in the morphine group. During the first 24 h postoperatively the buprenorphine group was given an average of 3.8 doses compared with 2.3 in the pethidine group (P greater than 0.05). It is concluded, that buprenorphine sublingually is as good as morphine intramuscularly for premedication and therefore should be recommended to patients who wish to avoid injections. For postoperative pain relief the initial dose of buprenorphine should be given intravenously. Only minor and unimportant side effects were seen.

A comparison of morphine and buprenorphine for analgesia after abdominal surgery

Eighty fit adults having elective abdominal hysterectomy or cholecystectomy received buprenorphine or morphine intravenously at the start of peritoneal closure, in a randomised double-blind trial. The anaesthetic sequence precluded the use of other narcotic analgesics. Pain scores were lower in patients who received buprenorphine, as were the cumulative numbers of patients withdrawn from the trial at each interval because of pain, statistical significance being achieved at all intervals from one to seven hours after administration. Unexpectedly, patients having the upper abdominal procedure were more likely to receive satisfactory analgesia than those having abdominal hysterectomy. Vomiting occurred more commonly after buprenorphine, and mean respiratory rates were slightly lower. However, the differences were not statistically significant. One patient with protracted drowsiness and slow respiratory rate after buprenorphine received naloxone. No serious side-effects were noted. Buprenorphine 4-6 micrograms/kg provided adequate postoperative analgesia of greater duration than could be achieved with morphine, and the potency of buprenorphine when administered in this way was at least 33 times that of morphine.

Postoperative analgesia in hip surgery. A controlled comparison of epidural buprenorphine with intramuscular morphine

In a randomised controlled trial, epidural buprenorphine was compared with intramuscular morphine for postoperative analgesia in patients after hip surgery. Analgesia was given on demand and consisted of epidural boluses of 60 micrograms of buprenorphine in 10 ml of normal saline or intramuscular morphine 0.15 mg/kg. Both forms of analgesia produced excellent pain relief as assessed by the linear analogue scoring system. In both quality and duration of pain relief, no significant difference was found between the two forms of analgesia, but the total dose of epidural buprenorphine required was five times less than the equivalent dose of intramuscular morphine. No side effects attributable to epidural buprenorphine administration were found. The authors conclude that low dose epidural buprenorphine provides an excellent alternative to intramuscular opiates for pain relief after hip surgery.