Intramuscular tramadol increases gastric pH during anesthesia.
OBJECTIVE
Tramadol, [(1RS, 2RS)-2-dimethylamino) methyl-1-(3-methoxyphenyl)-cyclohexanol hydrochloride], is an analgesic in clinical use. It has been reported that tramadol inhibits muscarinic type 3 receptor function, which primarily mediates smooth muscle contraction and glandular secretion. We investigated the effects of tramadol on the pH of gastric juices during anesthesia to determine whether tramadol inhibits secretion from the gastric glands.


METHODS
ASA physical status I or II adult patients (n = 30) presenting for major elective orthopedic surgery of the upper extremities or mastectomy were enrolled. Patients were randomly assigned to receive treatment with tramadol (n = 10), famotidine (n = 10), or saline (n = 10). General anesthesia was then induced using propofol, vecuronium bromide, and fentanyl. After inducing anesthesia, the gastric pH was measured using pH test paper and, then, 100 mg tramadol, 20 mg famotidine, or saline were injected into the deltoid muscle. Three hours after starting the operation, gastric juice was again aspirated and its gastric pH measured.


RESULTS
There were no differences in the pH before anesthesia between the three groups. By contrast, gastric pH was increased in the tramadol group by the same amount as it was in the famotidine group three hours after administering the drugs. Gastric pH of the saline, famotidine, and tramadol groups was 2.6 +/- 2.5, 6.3 +/- 2.0, and 6.4 +/- 0.8, respectively.


CONCLUSIONS
These results suggest that tramadol inhibits the secretion of gastric acid.
Minami
Kouichiro
K
Department of Anesthesiology, School of Medicine, University of Occupational and Environmental Health, Yahatanishiku, Kitakyushu, Japan. kminami@med.uoeh-u.ac.jp
Ogata
Junichi
J
Horishita
Takafumi
T
Shiraishi
Munehiro
M
Okamoto
Takashi
T
Sata
Takeyoshi
T
Shigematsu
Akio
A
D000328:Adult; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D000704:Analysis of Variance; D000897:Anti-Ulcer Agents / Q000008:administration & dosage; D017558:Elective Surgical Procedures; D015738:Famotidine / Q000008:administration & dosage; D005260:Female; D005500:Follow-Up Studies; D005750:Gastric Juice / Q000187:drug effects*; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007273:Injections, Intramuscular; D008297:Male; D008408:Mastectomy; D008875:Middle Aged; D012965:Sodium Chloride; D014147:Tramadol / Q000008:administration & dosage*; D034941:Upper Extremity / Q000601:surgery
D000701:Analgesics, Opioid; D000897:Anti-Ulcer Agents; D014147:Tramadol; D012965:Sodium Chloride; D015738:Famotidine