The
volume of distribution is decreased in elderly patients
. As a result, loading doses should be reduced by approximately 20%[60].
How does age affect drug distribution?
In general drug absorption, distribution in the body, activity, metabolism and excretion can all change as a result of ageing. The older person is
more likely to experience side effects
as well as experiencing difficulty in swallowing their medication.
What factors affect volume of distribution?
The major determinants of Vd are drug properties which affect protein binding and tissue binding. These consist of
molecule size, charge, pKa, and the lipid/water partition coefficient
.
How does VD change with age?
With ageing body
fat increases and total body water as well as lean body mass decrease
. Consequently, hydrophilic drugs have a smaller apparent volume of distribution (V) and lipophilic drugs have an increased V with a prolonged half-life.
How does increasing age influence pharmacokinetics?
With age,
body fat generally increases and total body water decreases
. Increased fat increases the volume of distribution for highly lipophilic drugs (eg, diazepam, chlordiazepoxide) and may meaningfully increase their elimination half-lives.
What factors can affect drug metabolism in an elderly?
Aging results in a number of significant changes in the human liver including
reductions in liver blood flow, size, drug-metabolizing enzyme content
, and pseudocapillarization. Drug metabolism is also influenced by comorbid disease, frailty, concomitant medicines, and (epi)genetics.
How are drugs distributed?
Drug distribution is
the disbursement of an unmetabolized drug as it moves through the body’s blood and tissues
. The efficacy or toxicity of a drug depends on the distribution in specific tissues and in part explains the lack of correlation between plasma levels and the effects that are seen.
What increases distribution volume?
Volume of distribution may be increased by
kidney failure
(due to fluid retention) and liver failure (due to altered body fluid and plasma protein binding). Conversely it may be decreased in dehydration.
What does volume of distribution depend on?
Apparent volume of distribution is dependent on
the drug’s lipid or water solubility, plasma protein binding as well as tissue binding
.
What is the significance of volume of distribution?
ABSTRACT: Volume of distribution is one of the most important pharmacokinetic properties of a drug candidate. It is
a major determinant of half-life and dosing frequency of a drug
. For a similar log P, a basic molecule will tend to exhibit higher volume of distribution than a neutral molecule.
What four routes are drugs excreted?
- Urine,
- Tears,
- Perspiration.
- Saliva.
- Respiration.
- Milk.
- Faeces.
- Bile.
How does gender affect drug effectiveness?
Pharmacodynamic differences in women include
greater sensitivity to and enhanced effectiveness of beta blockers, opioids
, selective serotonin reuptake inhibitors, and typical antipsychotics. Additionally, women are 50 to 75 percent more likely than men to experience an adverse drug reaction.
Which pharmacokinetic changes do adults experience with aging?
One of the most important pharmacokinetic changes associated with aging is
decreased renal elimination of drugs
. … Decreases in tubular function with age parallel those in glomerular function.
Which factors may contribute to unintentional nonadherence?
Common multivariate predictors of each of the three unintentional non-adherence behaviors included:
lower perceived need for medications, lower perceived medication affordability, younger age
, worse self-rated health, and diabetes or osteoporosis (relative to hypertension).
Does liver function decrease with age?
AGING AND LIVER VOLUME, BLOOD FLOW, AND FUNCTION
The volume and blood flow of the
liver gradually decrease with aging
. According to studies using ultrasound, the liver volume decreases by 20–40% as one gets older [4,9–11].
Why do drug handing varies for different age ranges?
Changes in drug distribution with ageing are due to:
Differences in body composition in the elderly
(e.g. reduced body water and increased body fat). Reduced serum albumin levels.
