Role of Pharmacokinetics in Addiction Treatment

Many people raise the question, what are pharmacokinetics? Pharmacokinetics is the journey a drug takes in the body.

What is Pharmacokinetics?

Knowledge of pharmacokinetics is not new. The history of pharmacokinetics dates to Germany in 1913 when researchers published an equation describing how enzymes metabolize drugs.1

What are Pharmacokinetics

The pharmacokinetics process is best described as what the body does to a drug. It describes several steps as the drug moves through the body, including absorption, distribution, metabolism, and excretion.2


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Pharmacokinetics vs. Pharmacodynamics

There is a difference between pharmacokinetics and pharmacodynamics, which describes what a drug does to the body. Understanding these terms means different things when considering the impact of specific medications used as part of a treatment program.

What is the Significance of Pharmacokinetics in Addiction Treatment?

The pharmacokinetics of drugs describes how the body interacts with and processes drugs. When people seek help to overcome addiction, providers need to know how the body reacts to each drug. Knowledge of each step of the pharmacokinetic process helps treatment providers develop effective treatment plans that involve medication assistance (MAT) with the least risk for harmful side effects.3

Lack of understanding surrounding the path a drug takes through the body may worsen symptoms for those undergoing drug and alcohol detox or medication-assisted addiction treatment.

Pharmacokinetics Analysis Processes

There are four steps of pharmacokinetics. Each describes the absorption and distribution of drugs throughout the body.


Absorption in pharmacokinetics describes the path a drug takes as it moves from the administration site (where it entered the body) to the site of action (the location in the body the drug is designed to affect). Also called medication absorption, absorption in pharmacokinetics helps determine how fast a drug is absorbed into the body. It also determines how much of the drug is absorbed.4


Pharmacokinetics distribution describes the drug’s path once it enters the bloodstream and travels to the tissues throughout the body.


Pharmacokinetics metabolism describes the metabolism of drugs by the body. Metabolism of drugs is the process the body uses to break down the drug making it easier for your body to excrete (remove it) from the body. A large part of the absorption and distribution of drugs throughout your body occurs in the liver.


When people talk about the excretion of a drug (removing the drug from the body), they often refer to the half-life of drugs as part of the process. The half-life of drugs is commonly addressed as part of the pharmacokinetic process to describe aspects of drug absorption and drug excretion (elimination).5

Factors for Extending Drug Absorption

Absorption is the pharmacokinetic phase that focuses on how the drug moves through the body. How fast the drug moves and how much of the drug is absorbed will vary depending on a few factors.6

Route of Administration

How the drug is administered (orally, intravenously, etc.) impacts how quickly it is available for the body to use. Some routes require time for the body to absorb the drug, whereas others offer instant availability.

Other factors that impact the effectiveness of absorption include specific drug-food interactions that change how the body interacts with a particular drug and the chemical properties and formulation.

Factors that Affect Drug Metabolism

Specific enzymes affect the pharmacokinetic process and, more specifically, how the body metabolizes drugs. Several factors impact how these enzymes work and how drugs are metabolized. The first factor is genetics. Specific genetic characteristics may affect whether someone metabolizes drugs quickly or more slowly.


Another factor unique to the individual is age. As we age, the speed of liver function slows, and therefore the rate at which the liver can metabolize drugs also slows. Conversely, infants and newborns with immature liver function may also metabolize drugs at a slower speed and require special dosing to ensure they are safe from an overdose.


Drug interactions (taking multiple drugs simultaneously) may impact enzyme function. Depending on the substances, metabolism speeds may be increased or decreased.

Factors That Affect Drug Excretion

The last of the steps of pharmacokinetics is excretion. During this pharmacokinetic phase, the liver (and other body systems) completely breaks down the drug and sends it to the kidneys. Most drugs are excreted through the urine. As with absorption and metabolization, certain factors impact how drugs are excreted.

Pathologies That Impact Renal Blood Flow

Because the pharmacokinetic phase of excretion relies heavily on the renal system, renal system diseases directly impact excretion. When someone has a renal system dysfunction, it could prolong the half-life of some drugs. This means the drug will remain active in the system longer, requiring adjustments to dosing to prevent adverse effects.
Disease processes that affect blood flow to the kidneys (renal blood flow) also affect excretion. Diseases such as congestive heart failure and liver disease negatively impact blood flow to the kidneys, which can then slow the process of drug excretion.6

Importance of Pharmacokinetics for Drug Companies and Patients

Importance of Pharmacokinetics for Drug Companies and Patients
An understanding of pharmacokinetics is vital at all levels. Drug companies must know how the drugs they produce and inevitably market to doctors and hospitals will work for patients. For providers, it is vital to clearly understand how each medicine works on its own and how it may positively or negatively interact with others.

Understanding pharmacokinetics is essential for patients as well. When patients are prescribed a drug (or take one over the counter), knowing how that drug will interact with any other prescription or non-prescription drugs is vital for avoiding a potentially dangerous drug interaction.

Knowledge of Pharmacokinetics

Whether one is a professional at a pharmaceutical company or a patient with a new prescription, a knowledge of pharmacokinetics can help in several ways.
  • Pharmacokinetics analyses help describe drug exposure timelines and drug interactions.
  • It can help medical and mental health providers determine accurate and safe dosing requirements.
  • It can also help providers modify dosing requirements based on the pharmacokinetic process for a specific drug or patient need. 
  • Pharmacokinetics helps providers offer an educated estimate on drug absorption and elimination rate.
  • Understanding the pharmacokinetic process also helps providers determine safety margins for drug dosing. 

Medical and Mental Health Providers

A clear understanding of pharmacokinetics is crucial to medical and mental health providers alike. Knowing how the body will process a particular drug is beneficial in developing safe and effective treatment plans that involve administering medications to those struggling with drug or alcohol addictions.

Due to the fact that many substances remain present in the body far longer than symptoms of their use, it is crucial to understand how each drug may interact with another when prescribing addiction treatment medications. Knowledge of each step of pharmacokinetics helps addiction treatment providers like ours here at Concise Recovery ensure each patient receives effective, accurate, and safe treatment.