Half life

Half-life is a term used in pharmacology and nuclear physics to describe the time it takes for a quantity to reduce to half its initial value. The term is commonly used in relation to the elimination of drugs or other substances from the body, as well as the decay of radioactive elements.

Pharmacology

In pharmacology, the half-life of a drug is the time it takes for the concentration of the drug in the body to be reduced by half. This is an important factor in determining the dosage and frequency of administration of a drug. The half-life of a drug can be affected by factors such as the drug's bioavailability, the rate of metabolism, and the individual's age, weight, and health status.

Nuclear Physics

In nuclear physics, the half-life is the time it takes for half of the atoms in a radioactive substance to decay. This is a key concept in understanding the behavior of radioactive materials, and is used in fields such as radiology, nuclear medicine, and nuclear engineering.

Calculation

The half-life of a substance can be calculated using the formula:

t_1/2 = (ln 2) / λ

where:

t_1/2 is the half-life

ln 2 is the natural logarithm of 2 (approximately 0.693)

λ is the decay constant

See Also

• Pharmacokinetics
• Radioactive decay
• Decay constant

References

Half life Resources
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