Thymopentin (TP-5) potency in vivo is enhanced by slow infusion

The in vivo activity of thymopentin in guinea pigs was assessed electromyographically 18 h after intravenous or subcutaneous injections or infusions ranging over varying periods of time. The lowest threshold dose required to establish a positive effect was obtained with a 30-60 min i.v. infusion (0.38-0.75 micrograms/kg) and we found that we needed X 5 times this dose with 30 min s.c. infusion, X 10 this dose with 10 min i.v. or s.c. infusion, X 200 this dose with bolus IV injection and X 400 this dose with bolus s.c. injection. The marked increase of potency of thymopentin with infusion should be considered in designing clinical regimens.