Effect of morphine, verapamil or morphine plus verapamil on lidocaine brachial block anaesthesia for orthopaedic surgery

Calcium channel blockers [CCBs] potentiate the analgesic properties of both local anaesthetics and opioids. We examined the analgesic effects of administering morphine, verapamil or its combination into the brachial plexus sheath with lidocaine in 64 unpremedicated patients of physical status 1 or 11, aged 20 - 55 yr and weighing 50 - 80 kg, undergoing upper extremity orthopaedic surgery. All patients received brachial plexus anaesthesia with 40 ml of 1.5% lidocaine and epinephrine 5 ug/ml. in addition, patients were randomly allocated to 1 of 4 groups; Group 1: patients received lidocaine solution, Group 2; patients received morphine 5 mg was added to lidocaine solution; Group 3; patients received verapamil 2.5 mg was added to lidocaine solution and Group 4; patients received morphine 5 mg and verapamil 2.5 mg were added to lidocaine solution. Onset of sensory block, duration of anaesthesia and analgesia were recorded. Postoperatively patients rated their pain [0 - 10] at 1, 6, 12, and 24 hr. Patients were instructed to take paracetamol tablets, every 6 hrs when pain score exceeded 3, and total postoperative analgesia requirements was recorded. Onset of sensory block was similar in the four treatment groups. Duration of anaesthesia [time of abolition of pinprick response] was significantly [p<0.001] increased in those patients receiving brachial plexus blocks with verapamil [groups 3 and 4]. Analgesic duration was significantly increased [p<0.001] in those patients receiving brachial plexus block with morphine [groups 2 and 4]. The total 24hr paracetamol use was also less in those groups [2 and 4], which was significant [p<0.05]. We conclude that, the addition of verapamil to brachial plexus block with lidocaine can prolong the duration of sensory anaesthesia, but it had no effect on analgesic duration of morphine used when both were administered with lidocaine via a brachial plexus route

Effects of antidepressants on morphine withdrawal

The acute and chronic effects of paroxetine and fluoxetine on naloxone- withdrawal-induced place aversion in morphine dependent rats were investigated. Acutely administered fluoxetine [25 mg/kg, s.c., given 30 min prior to naloxone withdrawal pairing] and chronic daily paroxetine [10 mg/kg, s.c.] co-administration with a morphine induction protocol, both attenuated morphine withdrawal place aversion. Conversely, acutely administered paroxetine [up to 25 mg/kg, s.c.] or chronic daily fluoxetine [10 mg/kg, s.c.] co-administration with morphine did not modify subsequent withdrawal place aversion. Previous radiologand binding studies have indicated that fluoxetine has opioid-displacing properties. It is suggested therefore that acute fluoxetine may have decreased withdrawal aversion, probably through serotonin and also, in part, via an opioid-like mechanism whereas chronic paroxetine decreased withdrawal aversion by a serotonergic mechanism, but it is not clear whether opioid systems play any role in the action of paroxetine