Vd of drugs equally soluble in water and oil (such as aminoglycosides) is slightly increased in obesity. Also, because distribution of a drug between adipose tissue and other tissues influences pharmacokinetics in obese patients, loading dose should be adjusted for IBW.
How does obesity affect drug distribution?
In obese individuals, blood flow to fat is even poorer. Obese individuals are also likely to have a degree of heart failure which further decreases blood flow. This makes their fat a large compartment of potential distribution for lipophilic drugs which fills gradually, and then becomes a slowly emptying reservoir.
How can a high BMI affect the distribution of thiopental?
In obese patients, thiopental has an increased Vd and a longer elimination half life (t1/2), but Cl values are unchanged. It was stated in as long ago as 1969 that thiopental dosage should be based on LBM.
Does gentamicin distribute easily into fat tissue?
Gentamicin is highly hydrophilic, i.e. not distributed into body fat and minimally distributed into tissue fluids.
Is drug clearance affected by obesity?
Drug clearance is greater in obesity and correlates with lean body weight. Body size metrics help guide dose selection, but there are advantages and disadvantages to all of them. Chronic dosing using total body weight can lead to drug toxicity.
Does BMI affect drug absorption?
Physiological changes due to obesity that affect this route generally include increases in gastrointestinal blood perfusion, higher cardiac output, increased splanchnic blood flow, changes in enterohepatic recirculation, accelerated gastric emptying, and increased gut permeability, all of which can alter both the rate …
How does weight affect drug effectiveness?
Changes in body weight can influence the amount of medicine you need to take and how long it stays in your body. The circulatory system may slow down, which can affect how fast drugs get to the liver and kidneys.
Is there a weight limit for anesthesia?
Most patients — overweight or not — had no problem with anesthesia. However, there were 380 reported cases of problems with anesthesia. Obese patients accounted for a significant proportion of those cases.
How does obesity affect vancomycin dosing?
In addition to an increase in body mass, obesity is associated with an increase in certain circulating proteins, which results in altered free serum vancomycin concentration.
Is Propofol hydrophilic?
Propofol lipid emulsion and fentanyl citrate are hydrophilic formulations of hydrophobic drugs that are frequently injected separately and sequentially for anesthesia.
What are the symptoms of gentamicin toxicity?
Side-Effects and Symptoms of Gentamicin Toxicity (also called Gentamicin Poisoning)
- Kidney damage and renal failure.
- Nerve damage.
- Ototoxicity (damage to the ear, such as hearing loss, vertigo or ringing in the ears (tinnitus)
- Balance problems.
- Problems with memory, concentration and fatigue.
- Oscillopsia (bouncing vision)
When should gentamicin levels be checked?
Pre-dose (trough) gentamicin levels should be checked after 24 hours and then twice weekly (target <1mg/L). Peak gentamicin levels, taken one hour after administration, can also be measured (target 3–5mg/L). Individualised dosing based on the patient’s pharmacokinetics can also be used.
How long does gentamicin stay in the body?
The serum half-life of gentamicin is approximately 2-3 hours in adults with normal renal function. It is prolonged in patients with impaired renal function and in premature or newborn infants.
Does obesity increase volume of distribution?
In obese compared with normal weight individuals, the total volume of distribution (Vd) is moderately increased (aminoglycosides, caffeine) or similar (H2-blockers, neuromuscular blockers), but the Vd corrected by kilogram of actual bodyweight is significantly smaller.
How does genetics affect drug response?
Because of their genetic makeup, some people process (metabolize) drugs slowly. As a result, a drug may accumulate in the body, causing toxicity. Other people metabolize drugs so quickly that after they take a usual dose, drug levels in the blood never become high enough for the drug to be effective.
How does age affect drug response?
Distribution of a medication is also affected by impaired absorption, which influences its onset, strength, and duration. In general, as we age, total body water and muscle mass decrease while percentage of body fat increases. These changes can lead to drugs having a longer duration of action and increased effect.