Melatonin

Dosage
The minimum dosage for melatonin is 0.003 mg/kg
Dosage is 0.05 mg/kg.
Melatonin levels can go as high as 1,000% at 1 mg and 10,000% at 3-5 mg
Half-Life
The half-life of melatonin is 38.15489 minutes.
Peak Time
Melatonin reaches a peak affect in about 19 minutes.
Constant absorption rate
Melatonin absorption half-life: 6 minutes
Decay rate
Melatonin decay rate is: ~0.018 minutes
Volume of distribution is 1.2 L/kg and clearance rate is 0.0218 L/min
Basal values in morning 10 pg/mL
Basal values at night 60 pg/mL
Oral bioavailability 15%
LD50 i.p. mouse 1168 mg/kg (1131 mg/kg in rat)
LD50 oral mouse 1250 mg/kg (>3200 mg/kg rat)
LD50 s.c. mouse >1600 mg/kg (same for rat)
LD50 i.v. mouse 472 mg/kg (rat 356 mg/kg)

In Dogs:

Half-life: 5 hours

Tmax: 20 minutes

Distribution phase time: 3.5 hours

Absorption half-life: 5 minutes

 

Source: https://pubmed.ncbi.nlm.nih.gov/7193238/