Pregabalin: Pharmacokinetics & Mechanism of Action

Instructor: Charity Hacker

I am a nursing instructor with over 20 years of nursing experience and a Masters Degree in Nursing Education.

Pharmacokinetics and mechanisms of actions are two very important descriptors when it comes to understanding drugs. In this lesson, we will learn all about how pregabalin works and what the body does with this drug.

Pregabalin as a Bully

Have you ever known someone who was a bully but surprised you by sticking up for the little guy? That's kind of how pregabalin is. It's a bully and you are the little guy. Why are you the little guy? Because you are in pain. Pain is picking on you and it won't leave you alone. Why does that make pregabalin a bully? Pregabalin is primarily indicated for use with pain related diagnoses. It can also be used as an anticonvulsant and has other off label uses. We will explore its mechanism of action to determine why, in this case, the bully has turned into the hero.

Mechanism of Action

Pain signals, along with those that cause convulsions or seizures, are passed from nerve to nerve through voltage-gated calcium channels that have alpha-delta subunits. Those with alpha-delta subunits are considered HVA or high voltage-activated channels. In the nerve cell, the calcium that passes through these channels excites the nerve cell and causes the transmission of the signal across the synapse to the next nerve cell.

The alpha-delta subunit can usually be found on the presynaptic section of nerve cells. What does that mean? The synapse, or the synaptic gap, is where a signal is passed from one nerve cell to another. So, if something blocks a signal in the presynaptic region of a cell, it modifies or stops the transmission of the signal to the next nerve. This is where pregabalin comes in, it binds to the subunit blocking the passing of calcium which reduces or stops the signal for pain or convulsions.

In this picture, the axon of the nerve cell indicates the presynaptic area.
Picture of a nerve cell synapse.

In our scenario, you are being picked on by pain, which is carried by calcium through the calcium channel. The door to the calcium channel is labeled the alpha-delta subunit. Pregabalin acts like a big bully to the pain because it blocks the door and refuses to let the calcium by. But, it is a hero to you because when it attaches to the door and refuses to let the pain by, it stops the pain signal.

Pregabalin's actions are described medically as antinociceptive and anticonvulsant. This means its actions prevent or reduce pain and convulsions. Some evidence shows that it may affect epinephrine and serotonin in the central nervous system, which includes the spinal cord and the brainstem.

Pharmacokinetics of Pregabalin

What exactly is pharmacokinetics? In science, kinetics refers to the study of motion and its causes. Combine this with pharmaco-, which deals with the use of drugs in medicine, and we get the study of how medicine moves through the body and what forces act on it causing it to do so. The primary categories of pharmacokinetics are absorption, distribution, and elimination. These categories can be further divided into more specific measures, such as time frames.

Absorption of Pregabalin

Pregabalin is taken by mouth with or without food and quickly absorbed in the stomach. The presence of food does slow the absorption of pregabalin but does not prevent it. In the end, the same amount is absorbed within approximately 40-80 minutes. Pregabalin is not a fast acting medicine, so since the same amount is absorbed ultimately, it does not matter if the patient has eaten or not.

Distribution of Pregabalin

Bioavailability describes how much of a medicine makes it from the point of administration into the blood stream. In the case of pregabalin, it is 90%. The volume of distribution helps the pharmacist and doctor determine the appropriate dose of the drug. Pregabalin's Vd or volume of distribution is 0.5 L/Kg. This gives the prescriber an idea of the volume needed for absorbing all of the medicine.

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