Have you ever heard the term ”psychoactive drugs?” Drugs in this category act on the central nervous system and alter its normal, everyday activity, causing changes in mood, awareness, and behavior.

People use drugs for many different reasons. These may be for fun or excitement; to feel good, better or different; to counteract negative feelings; because they are bored or curious; because their friends or family do it; or because they have a dependence on the drug.

Many psychoactive substances are used for their mood and perception altering effects, including those with accepted uses in medicine and psychiatry. Examples of psychoactive substances include caffeine, alcohol, cocaine, LSD, nicotine and cannabis.

Some of the many risks associated with drug abuse include death or injury from an overdose, but the greatest risk associated with psychoactive drugs is the loss of control which comes with addiction.

Caffeine

Caffeine is a psychoactive (mind-altering) drug that affects how we think and feel. It is a stimulant that speeds up our breathing, heart rate, thoughts and actions. Caffeine is found in the seeds, leaves and fruit of certain shrubs, including coffee and tea plants.

Psychoactive, also called psychotropic, is a term that is applied to chemical substances that change a person’s mental state by affecting the way the brain and nervous system work. This can lead to intoxication, which is often the main reason people choose to take psychoactive drugs.

There are four main groups of psychoactive drugs: stimulants, depressants, narcotics, and hallucinogens.

After being taken into the body by oral ingestion, smoking, injection, or snorting, the psychoactive chemicals in drugs move through the bloodstream and pass through the blood-brain barrier.

Barbiturates increase the activity of a chemical in the brain that helps transmit signals. This chemical is known as gamma amino butyric acid (GABA). As a medication, they reduce muscle spasms, relieve anxiety, prevent seizures, and induce sleep.

Intravenous (IV) drug use in which the drug is injected directly into a vein and enters the bloodstream to reach the brain. This is the quickest way of achieving a psycho-active drug effect. The drug effect is experienced in less than one minute.

For these reasons, most drugs are absorbed primarily in the small intestine, and acids, despite their ability as un-ionized drugs to readily cross membranes, are absorbed faster in the intestine than in the stomach (for review, see [1]).

In most instances, increasing the rate of gastric emptying and gastro-intestinal motility increases the rate of absorption of a drug but, for digoxin and riboflavin, increased gastrointestinal motility is associated with a decrease in the rate of absorption.

Even further, 94 to 97% of a drug will have been eliminated after 4 to 5 half-lives. Thus, it follows that after 4 to 5 half-lives, the plasma concentrations of a given drug will be below a clinically relevant concentration and thus will be considered eliminated.

However, there are numerous other drugs with very long half-life, examples are mefloquine 14–41 days (25), amiodarone 21–78 days (26), and oritavancin 393 h (27). Furthermore, what can be called “long half-life” is always relative to the length of the sampling period.

The elimination half-life of a drug is a pharmacokinetic parameter that is defined as the time it takes for the concentration of the drug in the plasma or the total amount in the body to be reduced by 50%. In other words, after one half-life, the concentration of the drug in the body will be half of the starting dose.

The half-life of a drug is the time it takes for the amount of a drug’s active substance in your body to reduce by half. This depends on how the body processes and gets rid of the drug.

A drug’s half-life is an important factor when it’s time to stop taking it. Both the strength and duration of the medication will be considered, as will its half-life. This is important because you risk unpleasant withdrawal symptoms if you quit cold turkey.

Half-life (symbol t1⁄2) is the time required for a quantity to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive.

Half-life, in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay (change spontaneously into other nuclear species by emitting particles and energy), or, equivalently, the time interval required for the number of disintegrations per second of a radioactive …

Effects of varying the dose interval A dosing interval of about a half-life is appropriate for drugs with half-lives of approximately 8-24 hours allowing dosing once, twice or three times daily. It is usually not practicable to administer drugs with shorter half-lives more frequently.

This shows that the population decays exponentially at a rate that depends on the decay constant. The time required for half of the original population of radioactive atoms to decay is called the half-life. The relationship between the half-life, T1/2, and the decay constant is given by T1/2 = 0.693/λ.

The time taken for the reactant species to reduce to half of its initial concentration is known as the half-life period of the reaction. At the half-life, 50% of the reaction is completed.

What Is Average Life? The average life is the length of time the principal of a debt issue is expected to be outstanding. In loans, mortgages, and bonds, the average life is the average period of time before the debt is repaid through amortization or sinking fund payments.

Answers. The half-life is 96 seconds. Since this is a zero-order reaction, the half-life is dependent on the concentration. In this instance, the half-life is decreased when the original concentration is reduced to 1.0 M.

Half-Life. Since the half-life equation of a first-order reaction does not include a reactant concentration term, it does not rely on the concentration of reactant present. In other words, a half-life is independent of concentration and remains constant throughout the duration of the reaction.