Preclinical evaluation of pharmacokinetics and safety of melatonin in propylene glycol for intravenous administration.
Melatonin is a highly effective treatment in different animal models of excitotoxicity or ischemia/reperfusion injury. Due to a lack of patentability, commercial sponsors are not interested in funding clinical evaluations of melatonin. Investigators may initiate small-scale clinical evaluation, and intravenous (i.v.) administration is appropriate in acute stroke patients. Institutional Review Boards may require proper preclinical evaluation of the preparation. In this pharmacokinetic and safety study, melatonin in propylene glycol was evaluated in adult male Sprague-Dawley rats. Following a single i.v. injection at 5 or 15 mg/kg, plasma concentrations of melatonin increased to 39 and 199 million pg/mL at 2 min and 128,000 and 772,000 pg/mL at 120 min. Within 60 min of injection, the blood pressure, heart rate and body temperature remained unaffected. Melatonin at 5 mg/kg did not influence the complete blood counts at 60 min, but melatonin at 15 mg/kg had some effects on the differential white cell and platelet counts. Melatonin at 5 or 15 mg/kg slightly elevated some liver enzymes at 60 min of injection, and melatonin at higher dose also elevated plasma creatinine and lactate dehydrogenase levels. At 24 hr after completion of six daily injections of melatonin, there was a 5.5% reduction in body weight. Gross postmortem examination and histological examination of the brain, kidney, liver and spleen did not reveal any evidence of toxicity. In conclusion, melatonin in propylene glycol markedly elevates plasma levels of melatonin with no serious toxicity. This preparation should be further evaluated in human patients.
Cheung
Raymond Tak Fai
RT
Division of Neurology, University Department of Medicine, Faculty of Medicine, The University of Hong Kong, Pokfulam. rtcheung@hkucc.hku.hk
Tipoe
George L
GL
Tam
Sidney
S
Ma
Edmond Shiu Kwan
ES
Zou
Liang Yu
LY
Chan
Pui Shan
PS
D000818:Animals; D001772:Blood Cell Count; D001794:Blood Pressure / Q000187:drug effects; D001831:Body Temperature / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D001921:Brain / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D064420:Drug-Related Side Effects and Adverse Reactions; D006339:Heart Rate / Q000187:drug effects; D007275:Injections, Intravenous; D008297:Male; D008550:Melatonin / Q000008:administration & dosage* / Q000009:adverse effects / Q000097:blood / Q000493:pharmacokinetics*; D019946:Propylene Glycol; D051381:Rats; D017207:Rats, Sprague-Dawley
D019946:Propylene Glycol; D008550:Melatonin