AIM To study and compare
pharmacokinetics (PK) afte r epidural or intravenous (iv)
administration of < 125 I>labeled
Huwento xin-1 (< 125 I>HWTX-1) in rhesus monkeys. METHODS H uwentoxin-1 was labeled by iodogen method and was administered at a dose of 0 388 MBq·kg -1 by lumbar puncture at the third lumbar (L 3) and the forth lumbar (L 4) interspaces using a 12-gauge paracentetic needle into epidural sp ace of rhesus monkeys or iv at the same dose. Reverse Phase High Performance Liq uid Chromatography (RP-HPLC) determined serum < 125 I>Huwentoxin-1 w ith an automatic gamma counter. RESULTS The puriation of < 125 I>Huwentoxin-1>96% and with the same bio-activity as unlabeled Huwen toxin-1; Radioactivity detected in epidural space was 38% of injected radioacti vity at 10 min after epidural injection, which demonstrated successful administr ation into epidural space; The maximum serum concentration after epidural or iv
administration of < 125 I>labeled Huwentoxin-1 were determined to be (0 70±0 04) MBq·L -1 and (4 98±0 58) MBq·L -1 , respectively, a t the maximum serum concentration times of 30 min and 2 min. Terminal T 1/2 after epidural or iv administration were (10 36±0 27) h or (11 03±1 16) h, respectively. Cls was (1 29±0 07) L·h -1 ·kg -1 or (1 25± 0 23) L·h -1 ·kg -1 , respectively. Bioavailability after epidural a dministration was(95±5)%. CONCLUSION Concentration-time cur ves of < 125 I> labeled Huwentoxin-1 after two routes were different. The degradation profiles after epidural and iv injection supported the using of HWTX-1 as analgesic by epidural administration.