Robert T. Fremeau Jr., PhD, possesses over 20 years of experience in the field of drug discovery in academic and industrial settings. As managing director of NeuroRX Consulting, Robert T. Fremeau Jr., PhD, offers consultation services to pharmaceutical and drug development companies regarding a variety of subjects, including matters associated with pharmacokinetics, the study of how the body processes drugs. Dr. Fremeau can be reached by email at rfremeau@neurorxconsulting.com.

2.  Robert T. Fremeau Jr., PhD, possesses over 20 years of
experience in the field of drug discovery in academic and
industrial settings. As managing director of NeuroRX
Consulting, Robert T. Fremeau Jr., PhD, offers consultation
services to pharmaceutical and drug development
companies regarding a variety of subjects, including
matters associated with pharmacokinetics, the study of
how the body processes drugs. Dr. Fremeau can be
reached by email at rfremeau@neurorxconsulting.com.
Pharmacokinetic studies involve the observation of four
primary processes that occur within the body after a drug
enters it: absorption, distribution, metabolism, and
excretion (ADME). Once a drug enters the body, it moves
across membranes during all four processes.

3.  Therefore, scientists must ensure its properties allow it to
dissolve into each membrane’s bilayers. After drug
administration, absorption is the first process to begin.
During the absorption process, the drug moves from its
administration site into the blood stream. Molecule size
significantly impacts the method of absorption, as smaller
molecules diffuse quicker than larger ones. Therefore,
while the body absorbs smaller molecules through passive
absorption, larger molecules require a carrier to mediate
transport. Once the blood absorbs the drug, it begins
distributing it throughout the body. At this stage, scientists
monitor the drug’s ability to enter the body’s various
internal systems and cells.

4.  The process of metabolism, which serves to prepare
the drug for elimination from the body, occurs after
the appropriate areas of the body receive the drug.
Due to their status as foreign substances, drugs and
chemicals must be filtered out of the body in order to
prevent adverse effects, such as drug toxicity.
Metabolism uses enzymes to alter a drug’s chemical
properties and convert it to a hydrophilic state,
thereby allowing the kidneys to dispel it. Metabolized
drugs leave the body through a variety of means. For
instance, drugs may be excreted via urine, tears,
sweat, or saliva. Patients with kidney or liver problems
may require additional monitoring by health
providers to avoid drug toxicity.