Morphine Chloroprocaine

Chloroprocaine can reduce the efficacy of epidural morphine and fentanyl analgesia. Bupivacaine may enhance the local anaesthetic effect of fentanyl, but does not appear to affect respiration. Similarly, Udocaine does not appear to increase respiratory depressant effects of morphine. However, two cases of respiratory depression have been reported with Udocaine and opioids. Morphine given as an intravenous bolus does not alter Udocaine serum levels given as a continuous intravenous infusion. 

Two studies " have found that chloroprocaine decreases the duration of epidural morphine analgesia (16 hours for chloroprocaine compared with 24 hours for lidocaine ). Another study found that morphine requirements after caesarean section were much higher in women who had received chloroprocaine for epidural anaesthesia than in those receiving Udocaine. The authors of one of the studies suggest that chloroprocaine should be avoided if epidural morphine is used. Epidural fentanyl also appears to be antagonised by chloroprocaine. ... 

Phan CQ, Azar I, Osborn IP, Lear E. The quality of epidural morphine analgesia following epidural anesthesia with chloroprocaine or chloroprocaine mixed with epinephrine for cesarean delivery. AnesthAnalg (1988) 67, S171. 

Karambelkar DJ, Ramanathan S. 2-Chloroprocaine antagonism of epidural morphine analgesia, ActaAnaesthesiolScand( 997) 41,774-8. 

Epidural chlorprocaine the efficacy and duration of epidural morphine analgesia is diminished when administered after 2-chloroprocaine compared with lidocaine. The mechanism of the interaction between 2-chloroprocaine and morphine is unknown. The observed interaction between epidural morphine and 2-chloroprocaine may be a result of differences in onset and duration of action of the two drugs. 

The addition of morphine and fentanyl to intrathecal and epidurally administered local anesthetics decreases local anesthetic dose requirements while reducing surgical and post-operative pain intensity. One exception is chloroprocaine, which may antagonize epidural opioid analgesic effects. 

---