Propranolol combined with dopamine has a synergistic action in intensifying and prolonging cutaneous analgesia in rats.
BACKGROUND
The purpose of the experiment was to assess interactions of dopamine with propranolol as an infiltrative anesthetic.


METHODS
After injecting the rats with four doses of drugs subcutaneously, the cutaneous analgesic effect of propranolol was compared with dopamine through the blockade of cutaneous trunci muscle reflex (CTMR) in response to local skin pinprick. Drug-drug interactions were examined via an isobolographic analysis.


RESULTS
We demonstrated that the action of propranolol and dopamine was dose dependent to skin infiltrative analgesia. On the ED(50) (50% effective dose) basis, the rank of drug potency was propranolol (11.3 [10.6-12.2]μmol) > dopamine (195 [188-205]μmol) (p < 0.001). At the equi-anesthetic doses (ED(25), ED(50), ED(75)), the block duration caused by dopamine was equal to that caused by propranolol. Coadministration of dopamine and propranolol exhibited a synergistic effect on infiltrative cutaneous analgesia.


CONCLUSIONS
The preclinical data showed that dopamine produced a lesser potency but a comparable duration of cutaneous analgesia compared to propranolol. Adding dopamine to propranolol potentiated and prolonged propranolol's cutaneous analgesic effect.
Department of Physical Therapy, Graduate Institute of Rehabilitation Science, College of Health Care, China Medical University, Taichung, Taiwan; Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan.
Yu-Wen
YW
Chen
Department of General Surgery, Chi Mei Medical Center, Tainan and Liouying, Taiwan; Department of Electrical Engineering, Southern Taiwan University of Science and Technology, Tainan, Taiwan.
Chong-Chi
CC
Chiu
Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Yu-Lei
YL
Wei
Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan, Taiwan. Electronic address: chhung@mail.ncku.edu.tw.
Ching-Hsia
CH
Hung
Department of Medical Research, Chi Mei Medical Center, Tainan, Taiwan.
Jhi-Joung
JJ
Wang
D000698:Analgesia / Q000379:methods*; D000772:Anesthesia, Local / Q000379:methods*; D000818:Animals; D004298:Dopamine / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D007279:Injections, Subcutaneous; D008297:Male; D011433:Propranolol / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D012867:Skin / Q000187:drug effects*; D013997:Time Factors
D011433:Propranolol; D004298:Dopamine
Cutaneous analgesia; Dopamine; Isobolographic analysis; Propranolol; Skin pinprick