1 The normal value for the partial pressure of arterial oxygen (PaO2) irrespective of age is greater than 80 mmHg/10.6 kPa (Mellengard K, 1966, Sorbini CA et al, 1968).2  The normal PaO2 for a given age can be predicted from: -. The normal value for the partial pressure of arterial oxygen (PaO2) irrespective of age is greater than 80 mmHg/10.6 kPa (Mellengard K, 1966, Sorbini CA et al, 1968).
When to take: Depending on the severity of the sleep problem, take time-released melatonin 1 to 3 hours prior to the time you usually fall asleep. Since time release melatonin only lasts for 3 â 4 hours, any need to shift sleep schedules more than 3 hours may require taking another pill in 3 or 4 hours. Cautions: Melatonin should not be taken if eyes are exposed to bright sunlight, and melatonin should be avoided if operating any vehicle. If attempting sleep shifts of more than 1 hour, light therapy should also be used. Do not use melatonin for more than two weeks at a time.
Recommended dosage, active amounts, other details. For regulating the sleep cycle, doses of melatonin between 500mcg (0.5mg) and 5mg seem to work. Start with 500mcg, and if it doesnât work, work up to 3-5mg. The benefits of melatonin are not dose-dependent - taking more will not help you fall asleep faster.