Conscious sedation: Pharmacology.
The pharmacokinetics of infusions

ADVANCED

Pharmacokinetics is the study of how drugs are absorbed, distributed, metabolised, and excreted by the body.

The pharmacokinetics of infusions related to sedation depend on several factors, including the drug being infused, the dose, the rate of infusion, and the patient's individual pharmacokinetic characteristics.

In general, when a drug is administered by infusion, it is delivered continuously over time, which can result in more predictable and stable blood levels of the drug compared to other routes of administration, such as oral, transmucosal, or bolus IV injection.

When a sedative drug is given as an infusion, it is administered over a longer period of time, maintaining a constant concentration in the blood.

A bolus injection is given all at once, so it starts with a very high concentration (possibly sedation too deep) and as the drug is metabolised the concentration drops (possibly too light).

The pharmacokinetics of an infusion varies depending on factors such as

• the rate of administration,
• the duration of infusion,
• the drug's half-life.

In terms of pharmacokinetics, infusions can result in more predictable and stable drug levels in the blood, as compared to bolus injections. This is particularly important in the context of sedation, where maintaining a consistent level of sedation is important for patient safety.

Some sedative drugs, such as propofol, are normally administered as continuous infusions due to their rapid onset and short duration of action. Other drugs, such as opioids, may be administered via bolus injections or infusions, depending on the desired effect and the patient's individual needs.

Clearance

The clearance of sedative drugs, or the rate at which the drug is eliminated from the body, is an important pharmacokinetic parameter to consider when administering infusions. Factors that can affect clearance include the patient's age, weight, renal and hepatic function, and the presence of any comorbidities. It is important to monitor the patient's response to the infusion and adjust the rate of administration as needed to maintain the required level of sedation.

Understanding the pharmacokinetics of sedative infusions is important to ensure safe and effective sedation for patients undergoing medical procedures or treatments.