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 …
How does obesity affect drug dosing?
Due to the increase in clearance in obese patients, the dose should be increased. The recommended dose of 1 g has been increased to 2 g in obese patients to ensure adequate exposure and may need to be administered more frequently.
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 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.
How does obesity 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.
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.
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.
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.
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.
What drugs accumulate in fat?
Drugs that dissolve in water (water-soluble drugs), such as the antihypertensive drug atenolol, tend to stay within the blood and the fluid that surrounds cells (interstitial space). Drugs that dissolve in fat (fat-soluble drugs), such as the antianxiety drug clorazepate, tend to concentrate in fatty tissues.
How does age factor affect drug metabolism?
Thus, age-related changes in drug metabolism should be considered a typical phenotypic characteristic of the aging process. Generally, older age is associated with increased blood concentrations of drugs and altered metabolism, reduced effectiveness, and increased risk of adverse reactions for many medications (2).
Does Weight Affect ibuprofen?
Ibuprofen volume of distribution was increased in obese subjects, and this increased distribution correlated positively with body weight (r = 0.82; P less than 0.001).
What is weight based dosing?
Weight-Based Dosing Errors
Medication dosing is often calculated on the basis of a patient’s weight, particularly for pediatric patients, who require individualized dose calculations based on their size.
How does disease affect drug action?
The absorption, distribution, metabolism, and elimination (ADME) of drugs can be influenced by the physiological and biochemical changes that occur due to various diseases. These changes can have dramatic influence on the exposure of drugs and lead to drug toxicity or lack of drug efficacy.
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.
What is ideal body weight definition?
Ideal body weight is the optimal weight associated with maximum life expectancy for a given height. Before the use of BMI to quantify obesity, TBW above 20% of IBW was defined as being obese.