Low-dose epidural morphine by infusion pump

δ-opioid receptor and somatostatin receptor-4 heterodimerization: possible implications in modulation of pain associated signaling

Pain relief is the principal action of opioids. Somatostatin (SST), a growth hormone inhibitory peptide is also known to alleviate pain even in cases when opioids fail. Recent studies have shown that mice are prone to sustained pain and devoid of analgesic effect in the absence of somatostatin receptor 4 (SSTR4). In the present study, using brain slices, cultured neurons and HEK-293 cells, we showed that SSTR4 and δ-Opioid receptor (δOR) exist in a heteromeric complex and function in synergistic manner. SSTR4 and δOR co-expressed in cortical/striatal brain regions and spinal cord. Using cultured neuronal cells, we describe the heterogeneous complex formation of SSTR4 and δOR at neuronal cell body and processes. Cotransfected cells display inhibition of cAMP/PKA and co-activation of SSTR4 and δOR oppose receptor trafficking induced by individual receptor activation. Furthermore, downstream signaling pathways either associated with withdrawal or pain relief are modulated synergistically with a predominant role of SSTR4. Inhibition of cAMP/PKA and activation of ERK1/2 are the possible cellular adaptations to prevent withdrawal induced by chronic morphine use. Our results reveal direct intra-membrane interaction between SSTR4 and δOR and provide insights for the molecular mechanism for the anti-nociceptive property of SST in combination with opioids as a potential therapeutic approach to avoid undesirable withdrawal symptoms.

Epidural meperidine after cesarean section: the effect of diluent volume

We investigated the effect of diluent volume on analgesia and systemic absorption from epidural meperidine after cesarean section in a randomized, double-blind study. At the first request for postoperative analgesia, 36 parturients were given epidural meperidine 25 mg diluted with saline to either 2 mL (12.5 mg/mL), 5 mL (5 mg/mL), or 10 mL (2.5 mg/mL). Visual analog pain scores measured in the first 30 min were greater in the 2-mL group compared with both the 5-mL group (P = 0.028) and the 10-mL group (P = 0.031). Onset of analgesia (time for visual analog pain scores to decrease by 50%) was also slower in the 2-mL group (17.5 min) compared with the 5-mL group (9 min; P = 0.015) and the 10-mL group (12 min; P = 0.003); there were no differences between the 5-mL group and the 10-mL group. Duration of analgesia and plasma concentrations of meperidine were similar among groups. No adverse side effects were recorded. Previous work has suggested that injection of epidural opioids in large volumes increases the potential risk of respiratory depression from cephalad spread of the drug. Therefore, we conclude that analgesia is optimum when epidural meperidine is administered diluted to 5 mL.

Overview of current development in patient-controlled analgesia

Over the past two decades, numerous trials have assessed the safety and efficacy of patient-controlled analgesia (PCA). Advantages over conventional parenteral narcotics reported from these trials include equivalent to superior pain relief, superior patient satisfaction, decreased sedation and anxiety, faster return to normal functional status, and reduction in nursing time and hospitalization. The majority of these trials have been conducted in the postoperative patient population. In the mid to late 1980s, interest arose in applying PCA technology to the management of cancer pain. Factors that served as an impetus for the use of PCA in cancer pain included favorable reports from the postoperative setting and the often-cited statistics regarding the magnitude of the cancer pain problem. Advances in PCA technology coupled with advances in vascular access technology that allow the placement of long-term ports and catheters to facilitate intravenous, epidural, or intrathecal administration of opioid analgesics have made the applicability of PCA in ambulatory cancer patients an attractive option. The greatest breakthrough in PCA technology came with the introduction of devices making it possible to choose between intermittent (demand bolus) and continuous administration (continuous infusion) or both intermittent and continuous modes. A comparison of these types of PCA devices is described. The limitations of the literature involving PCA therapy in cancer patients make it difficult to identify optimal patient selection criteria, PCA administration schedules, drug selection and dosing, and optimal route of administration. The current status and pertinent issues related to these topics are addressed.

Clinical experience of long-term treatment with epidural and intrathecal opioids--a nationwide survey

Long-term use of spinal opioids to treat chronic severe pain is widely established. However, the indications, shortcomings and complications of the method have not been completely described. Experience with spinal opioids was analysed for the period 1979-1984 in a nationwide Swedish survey. Out of 93 anaesthesia departments, 69 used the method. Approximately 750 patients were treated with epidural morphine for an average duration of 124 days (3-450). Eighteen patients were treated with intrathecal morphine for an average period for 47 days (3-90). The intrathecal approach was used in all clinics because of failure of the epidural route. In only one department was the intrathecal approach used as the primary route of therapy, depending on the mechanism of pain. The highest daily morphine dose was 480 mg and 50 mg for epidural and intrathecal routes, respectively. The patients given the highest dosages were not necessarily those subjected to the longest treatment. The need for increased dosage seems to be related not only to changes in receptor sensitivity but also to changes in pain mechanisms. No case of threatening ventilatory depression was reported. Thirty-two departments had treated a few patients with chronic non-cancer pain conditions. Initial results were considered "excellent" in 11 departments, but at follow-up results were excellent in only one department. In addition to dislocation, occlusion of the catheters or leakage, injection pain was an obstacle to successful treatment. Pruritus urinary retention, and local infections were not reported as significant problems, but one case of meningitis was reported.

Intraspinal morphine for cancer pain

From a survey of the recent literature on chronic intraspinal morphine administration for cancer pain concerning 412 cases, the present authors observe that: 1. data regarding follow-up on pain relief and complications are lacking; 2. continuous administration by closed systems shows more efficacy in long-term pain relief; 3. tolerance, although not reported by all authors, is present and becomes remarkable in prolonged administration; 4. serious side-effects are less frequent with the epidural administration technique. These data are confirmed by the present authors' clinical experience of 22 patients treated with epidural morphine administration and 53 patients treated with intrathecal morphine. The widespread use of these methods is limited not only by technical complications but also by the existence of certain types of pain which do not respond to morphine and which may develop, as part of the evolution of the neoplastic disease, even during treatment with intraspinal morphine.

Intrathecal somatostatin in terminally ill patients. A report of two cases

Intrathecal morphine has been shown to be reliable in producing analgesia in patients with intractable cancer pain. Recently, we have demonstrated that intrathecal somatostatin is as effective in the treatment of cancer pain as intrathecal morphine. This report presents 2 cases in whom analgesia could be maintained for 60 and 25 days, respectively, under continuous intrathecal infusion of somatostatin by means of infusion devices.