Pharmacokinetics of Insomnia Medicines

Last updated: March 28, 2019

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What is Pharmacokinetics?

Pharmacokinetics is a word that describes the movement of a drug into, through, and out of the body. It defines the time course of a drugs’ absorption, bioavailability, distribution, metabolism, and excretion. Pharmacokinetics is sometimes used to describe what the body does to a drug.

Are they the same for everyone?

No, the pharmacokinetics of a drug differs from one person to another. It depends on patient-related factors. These factors can affect what happens to a drug inside the body. These patient-related factors can help predict how a drug can behave in certain populations. Some of these patient-related factors include renal function, genetic makeup, sex, or age. For example, if a drug needs to get metabolized before it works, it can take longer an elderly patient to do so compared to a younger patient. This is because the elderly often have slower metabolism rate compared to their younger counterparts.

Aside from the patient-related factors mentioned above, other factors related to a patient’s physiology can also affect a drug’s pharmacokinetics. An individual who suffers from renal failure will have different pharmacokinetics compared to a healthy individual. The same way that an obese patient will have different pharmacokinetics compared to a slim patient.

Because of these individual differences, a doctor should prescribe a drug based on a patient’s needs and physical condition. A doctor can adjust the recommended dosage until the desired effects are met. However, such adjustments can delay the optimal response expected from those taking a drug. These adjustments can also result in adverse effects.

How can I understand Pharmacokinetics?

Before we take any medicine, we ask our doctor how it works and if there are any side effects. This allows us to prepare ourselves so we won’t get caught off guard. If you know that medication will make you feel drowsy then you can avoid doing tasks that require you to be alert. If a medication can cause vomiting, then you limit your food intake. You also ask your doctor if a medication contains any ingredient that you are allergic to so you can avoid endangering yourself.

Knowing a medication’s pharmacokinetics works the same way. Before you take a medication, you’d want to know what your body will do to it. Take a look at the table above. It’s a pharmacokinetics table of insomnia medications from the website of NPS MedicineWise, an independent Australian organization dedicated to improving health technologies. It lists the common hypnotics often used in treating insomnia. The table lists the name of the drug, its half-life, and the time before it reaches maximum concentration.

Let’s take Zaleplon as an example. In the table above, it lists the time to maximum concentration of the said medication to be 1 hour. This means that you should feel the maximum effect of the drug one hour after you take it. The next column is for the half-life of the drug. A half-life is how long it will take for the effects of the drug to go down to half of its maximum concentration. So, for Zaleplon, it will take 1 hour for you to feel its full effect and after another hour, the effects of the drug should have worn off by half.

Why do I need to understand pharmacokinetics?

What’s in it for you? Knowing these details will better equip you to handle an insomnia medication. Since you know that it will take an hour for Zaleplon to take full effect, you need to take it 30 minutes to an hour before going to bed. If you take it, say 2 hours before bed, you’ll be feeling sleepy even before you’re ready. Nitrazepam, on the other hand, takes 2 hours before it reaches maximum concentration. This means that you can take it 2 hours before going to bed. If you take it immediately before going to bed, you might spend 2 hours tossing and turning since the effects won’t set in yet.

The half-life of the drug is equally important. For Zaleplon, it’s 1 hour after the drug reaches maximum concentration. This means that if you plan to sleep for 7 hours, you know that the effects would have worn off by the time you awaken. This makes Zaleplon safer to take if you need to be alert the next day.

On the other hand, Nitrazepam has a half-life of 27 hours. You’ll be feeling the effects of the drug up to the next day. Since you have this information, you can plan your day ahead. You can avoid performing tasks that require you to be alert.

Knowing how a drug works and how long it works is vital. It lets you understand what will happen to your body once you pop that pill into your mouth. You know what to expect so you can prepare your body and ensure that you’re not performing any task that can get compromised because of how the drug works.

Pharmacokinetics sound complicated but it isn’t. Once you understand what it means, you can take advantage of your insomnia medication and its benefits without any uncertainties.

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