Determining the optimal regimen of a drug or vaccine — including dose of the amanuensis and schedule of administration — is an essential part of pharmaceutical research. It is also a requirement for approving from regulatory agencies including the U.s. Food and Drug Administrations (FDA) and European Medicines Agency (EMA).

The commencement stage of determining drug dosing begins in pre-clinical brute studies. From these studies, drug doses are converted to an estimated suitable dose for humans to be tested in phase I (first-in-human) trials. Phase I trials evaluate the safety of the agent in a small grouping of healthy volunteers and may as well include escalating doses to appraise toxicity and pharmokinetics.

Further dose investigation studies may be conducted in phase II trials. For these studies, groups of participants may be given different doses of the investigational amanuensis to determine the optimal therapeutic range. For whatsoever given drug, the everyman dose that induces the desired consequence with the fewest adverse events is an ideal target to progress to large phase Iii randomized trials to evaluate efficacy.

The liver is the principal site of drug metabolism and the rate of metabolism, along with assimilation, distribution, and excretion, affects drug concentration in the blood, impacting the drug's efficacy and toxicity. For example, if a drug is metabolized too quickly or has poor absorption, information technology may non exert its desired effect and a college dose may be needed for clinical benefit. If a drug is metabolized or excreted too slowly, its toxicity may outweigh its benefit. A drug that is metabolized or excreted speedily at a dose with reasonable efficacy/toxicity contour may be a candidate for more frequent assistants to keep the level of the drug in the body above a threshold to maintain clinical benefit.

Additionally, dosing is non always static for all populations and adjustments may exist necessary depending on clinical factors (such as renal function), other medications, age, and weight.

Vaccines go through a like sequence of clinical trials to determine optimal dosing regimens. In the Leap of 2020, trials were offset initiated to evaluate COVID-19 vaccine dosing. Pfizer/BioNTech concluded that 30 µg of their lipid nanoparticle-encapsulated mRNA was optimal, while Moderna settled on 100 µg. Because the Johnson & Johnson COVID-xix vaccine is adenovirus-vectored, their dosing is based on adenovirus particles (5x1010 viral particles/injection).

Further dose investigations in children revealed that two x µg doses of Pfizer/BioNTech vaccine was suitable for children five-11 years of historic period. The Moderna COVID-19 vaccine is not even so authorized for children in this age group in the United States, though they take filed for regulatory approval for two 50 µg doses (half dose compared to adults) in children aged 6-eleven years in Europe.

Lower doses of COVID-19 vaccines in children, however, is due to a more than robust immune system in younger people, meaning that less vaccine is required to induce a comparable allowed response.

It seems reasonable that the dose for COVID-19 vaccines in children is less than what is given for adults, all the same the rationale for dosing adjustments for vaccines in children is non the same every bit for drugs. Weight- and historic period-based adjustments for many medications are due to pharmokinetic profiles. That is, the claret concentration of many drugs varies by body weight. Lower doses of COVID-19 vaccines in children, however, is due to a more than robust immune system in younger people, meaning that less vaccine is required to induce a comparable allowed response. Several other vaccines are given at lower doses for children, including influenza vaccines. Additionally, some vaccines have special high-dose formulations for adults older than 65 years because of significant immune organization dysfunction related to aging.

The schedule of COVID vaccine dosing for vaccines with multiple injections is based upon decades of research on the kinetics of the immune response. Unlike the pharmokinetics of a drug, in which the activity of the drug is linked to presence of that amanuensis in the blood, a vaccine is meant to be a brusque-term bulletin. The body takes that bulletin and induces an immune response, which is a biological process that takes 10-14 days. This is the reason people aren't considered fully vaccinated until 14 days after their final primary COVID-19 vaccine dose.

Administering the 2d dose of vaccine likewise early tin interfere with the development of memory B cells and T cells, then Pfizer/BioNTech tested 21 days and Moderna tested 28 days in between immunizations. The iii-to-4-calendar week range was chosen for logistical reasons: to avert interference with the primary allowed response, nonetheless go people fully vaccinated as apace as possible. Notwithstanding, this does non mean this dosing interval is optimal. A study in the United Kingdom revealed that an extended dosing interval of Pfizer/BioNTech or AstraZeneca COVID vaccines (ix-12 weeks autonomously) resulted in higher antibody levels and meliorate protection than the standard dosing interval.

Drugs and vaccines need to be evaluated in clinical trials to determine adequate dosing regimens. In both situations, the corporeality of agent and schedule of assistants should have an acceptable efficacy/toxicity ratio.  However, the pharmokinetic profile of a drug weighs heavily into dosing decisions, while vaccine dosing is dependent on inducing an immune response that confers protection, which is prominently influenced by age.