Quick Answer: How does obesity affect 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 obesity affect drug distribution?

Increased volume of distribution for lipid-soluble drugs

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.

Does obesity increase VD?

Paracetamol Vd is increased in obesity and in males relative to females. Clearance increases with body weight and therefore is much greater in obese patients and males.

How does weight affect pharmacokinetics?

Pharmacokinetic changes in obese patients. Effect on absorption: Gastric emptying may be increased OR decreased (and it is unpredictable). Absorption from the subcutaneous compartment will be slowed due to poor blood flow to subcutaneous fat.

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How does obesity affect pharmacokinetics and pharmacodynamics?

Obesity-related changes in normal physiology, such as alterations in lipid content, plasma proteins, drug metabolizing enzymes, drug transporters, and blood flow, can affect the disposition (absorption, distribution, metabolism, and excretion) and pharmacodynamics of commonly prescribed drugs, thereby altering their …

What happens when an obese person is given with a lipophilic drug?

After redistribution, lipophilic drugs tend to accumulate in the fat mass. As a result, volume of distribution (Vd) for lipophilic drugs will increase in the obese. The loading dose of these drugs should therefore be based on TBW. Hydrophilic drugs will be primarily distributed to the muscle mass.

Does body weight affect drug absorption?

The distribution of a drug between fat and lean tissues may influence its pharmacokinetics in obese patients. Thus, the loading dose should be adjusted to the TBW or IBW, according to data from studies carried out in obese individuals.

How does obesity affect VD?

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 body weight affect drug doses?

When lean body weight increases there will be a corresponding increase in drug clearance and an increased dose may be required.

Which drugs are dosed by ideal body weight?

In general, lean body weight is the most appropriate dose for most anesthetic drugs, with the exception of NDMB, where ideal body weight may be more appropriate. Succinylcholine should be dosed to total body weight.

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When do you use ideal body weight and actual body weight?

If a patient’s actual body weight was less than his or her ideal weight, then actual weight should be used. However, if the patient is obese, then a correction is used.

How do you calculate ideal body weight?

Ideal body weight is computed in men as 50 + (0.91 × [height in centimeters − 152.4]) and in women as 45.5 + (0.91 × [height in centimeters − 152.4]). A simple alternative would be to compute ideal body weight as the weight corresponding to an ideal body mass index of 22 kg/m2.

Is total body weight the same as actual body weight?

Total Body Weight (TBW) is the patient’s actual weight. Ideal Body Weight (IBW): Males = height – 100.

What is optimal body weight?

According to the National Institutes of Health (NIH) : A BMI of less than 18.5 means that a person is underweight. A BMI of between 18.5 and 24.9 is ideal. A BMI of between 25 and 29.9 is overweight.

How does age affect drug absorption?

As age increases, the functions of tissues and organs in the body gradually decline. Due to this decline in organ function, drug absorption, distribution, metabolism and excretion (ADME processes) in elderly people are worse than those of young people.

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