Table 1.

Pharmacokinetic parameters of oxytocin in different species.

Dose	Absorption Kinetics		Pharmacokinetics	Species	Reference
	Administration Route	Evaluated Parameters
25 IU	IV	T1/2: 5.89 min., clearance rate of 11.67 L/min., and mean residence time of 7.78 min.	Maximum effective concentration of 0.45 ng/mL and a plasma concentration of 0.25 ng/mL	Mare	Steckler et al. [57]
10 IU	IM	Minimal plasma concentration at 20 min. of administration 4822 pg/h/mL.	Tmax = 1.13 ± 0.91 h, Cmax = 2662 ± 567 pg/mL, AUC = 4822 ± 728 pg/h/mL, T1/2 = 1.02 ± 0.33 h.	Rabbit	Zhu and Lal [63]
400 IU	Sublingual	Plasmatic concentration at 20 min. of administration 1234 pg/h/mL.	Tmax = 0.93 ± 0.64 h, Cmax = 1164 ± 1179 pg/mL, AUC = 1234 ± 1001 pg/h/mL, T1/2 = 0.90 ± 0.33 h.
0.33–1.32 IU	Intranasal	T1/2 = 12.2 min., Tmax = 12.2 min., Mean plasma concentration = 18.9 pg/mL.	Cmax = 77.3 pg/mL, AUC = 1726 pg/mL/min., mean residence time = 20 min.	Cow	Wagner et al. [64]
0.083, 0.11 and 0.17 IU	IM	T1/2 = 1–6 min. Bioavailability: 70–100%, Vss: 40 min.	Clearance rate 7.87 mL.	Sow	Mota-Rojas et al. [65], Hill [66]
40 IU 20 IU	IM IV Intravulvar	T1/2 = 1.94 ± 0.21 min.	Vd = 0.46 ± 0.02 L/kg, T1/2 of elimination = 22.3 ± 0.3 min.	Sow	Mota-Rojas et al. [67], Ybarra Navarro [68]

In the case of non-domestic species, the reported values for baboons receiving 500 IU IV OXT were a mean plasma concentration of 10 pg/mL on 10 min., T_1/2 = 1.1 ± 0.2 min, Vd = 80 mL/Kg, Vss = 200 mL/Kg, fraction of elimination = 34 ± 5%, and mean residence time = 7.7 ± 0.8 min. For rats receiving 200–1000 ng/Kg IV, T_1/2 = 21.09 min, T_1/2 elimination = 7.94 min, Vd = 0.13–0.80 L/Kg, Vss = 0.34–0.80 L/Kg, and AUC = 2219–80,087 h/ng/L. AUC: area under the plot of plasma concentration of a drug versus time after dosage; Cmax: peak plasma concentration; IU: international units; IM: intramuscular; IV: intravenous; T_1/2: half-life; Tmax: time to reach maximum concentration; Vd: volume of distribution; Vss: steady state volume of distribution.