1. Half Life Rtx
2. Half Life 2
3. Half-life Equation
4. Halflife2.net

Medically reviewed by Carmen Fookes, BPharm. Last updated on April 28, 2021.

Half-Life: Uplink, released February 12, 1999, is one of two demos released by Valve for the original Half-Life video game. The first was Half-Life: Day One and contained the first fifth of the full game, and was only included with certain video cards of the time. Half-Life: Uplink, on the other hand, was a standalone demo set in the Half-Life.

Nov 16, 2004 1998. HALF-LIFE sends a shock through the game industry with its combination of pounding action and continuous, immersive storytelling. Valve's debut title wins more than 50 game-of-the-year awards on its way to being named 'Best PC Game Ever' by PC Gamer, and launches a franchise with more than eight million retail units sold worldwide. Half-life: This is a simulation of the radioactive decay of 400 radioactive nuclei. You can choose from three different half lives. Note that the nuclei turn blue.

Half-life calculator | What is half-life | Patient-specific variables | Drug-specific variables | Short vs long half-life | Common substances and their half-lives

Drug Half Life / Clearance Calculator

Work out how long it takes for a drug to leave your body.

Half life Clearance

This is an estimate on the time it will take for a drug to be removed from the body.

The actual half-life of the same drug may vary significantly from person to person, because it depends on a number of different patient-specific and drug-specific variables.

This tool should NOT be considered as a substitute for any professional medical service, NOR as a substitute for clinical judgement. It should not be relied upon to predict the time period required to ensure a negative drug test result, because laboratory tests mostly test for drug metabolites.

What is the half-life of a Drug?

The half-life of a drug is an estimate of the period of time that it takes for the concentration or amount in the body of that drug to be reduced by exactly one half (50%). The symbol for half-life is t½.

For example, if 100mg of a drug with a half-life of 60 minutes is taken, the following is estimated:

• 60 minutes after administration, 50mg remains
• 120 minutes after administration, 25mg remains
• 180 minutes after administration, 12.5mg remains
• 240 minutes after administration, 6.25mg remains
• 300 minutes after administration, 3.125mg remains.

In theory, we can see that after 300 minutes, almost 97% of this drug is expected to have been eliminated. Most drugs are considered to have a negligible effect after four-to-five half-lives. However, this does not mean that won’t be detectable, for example, during a drug test. Just that they will have no effect.

In reality, the actual half-life of a drug varies from person to person, because it depends on a number of different patient- and drug-specific variables. These affect how well a particular drug is distributed around a person’s body (called the volume of distribution), or how fast a person excretes that drug (called the drug clearance). For example, the IV drug gentamicin, which is cleared through the kidneys, has a half-life of 2-3 hours in a young person with no kidney disease, but over 24 hours in somebody with severe kidney disease.

Generally, it is difficult to precisely say how long a drug or substance will take to be excreted from someone’s body. This is an important fact for athletes or people in occupations that require them to be substance-free to remember. Half-lives in the anti-doping world are of limited value because they do not reflect the presence of metabolites (break-down products from the parent drug), which are often what is measured in anti-doping tests. In addition, serum half-life does not necessarily reflect urine concentrations, which is the main sample of choice in drug testing.

Patient-specific variables that may affect half-life

• Age
• Blood circulation
• Diet (eg, grapefruit juice and several drugs, green vegetables and warfarin)
• Excessive fluid (such as in people with heart failure or edema) or low fluid levels (dehydration)
• Gender
• History of previous drug use
• Kidney function (for drugs that are cleared via the kidneys)
• Liver function (for drugs that are metabolized through the liver)
• Obesity
• Pre-existing conditions (such as heart failure, gastrointestinal disorders, pregnancy)
• Presence of drugs that compete for binding sites or interact in other ways
• Race/ethnicity (this can influence the metabolism of a drug)
• Smoking
• Other variables, such as if the person is on hemodialysis.

Drug-specific variables that may affect half-life

• Drug formulation (ie, modified or controlled release preparations extend half-life)
• How the drug behaves in the body (ie, zero order, first order or multi-compartmental pharmacokinetics)
• How the drug is administered (half-life may be different with IV administration, compared to intranasal or oral administration)
• How the drug is cleared from the body (eg, kidneys, liver, lungs)
• If the drug accumulates in fat or other types of tissue
• If the drug binds to proteins or not
• Presence of metabolites or other drugs that may interact
• Properties of the drug, including molecule size, charge, and pKa
• The volume of distribution of a drug
• Other variables, such as if the drug is actively transported, is self-induced, or has saturation pharmacokinetics.

Short versus long half-lives

Drugs or substances that have a shorter half-life tend to act very quickly, but their effects wear off rapidly, meaning that they usually need to be taken several times a day to have the same effect. Drugs with a longer half-life may take longer to start working, but their effects persist for longer, and they may only need to be dosed once a day, once a week, once a month, or even less frequently.

When considering drugs with a high addiction or dependence potential, those with a short half-life are typically harder to withdraw from than those with a long half-life. For this reason, drug treatment programs will often switch a person from a short-acting drug to a long-acting equivalent from the same class, in order to improve the withdrawal process.

List of common medicines or substances and their half-lives

* Note that half-life varies depending on source used. Half-life in this table refers to the elimination half life.

See Also

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Set between the events of Half-Life and Half-Life 2, Alyx Vance and her father Eli mount an early resistance to the Combine's brutal occupation of Earth.
The loss of the Seven-Hour War is still fresh. In the shadow of a rising Combine fortress known as the Citadel, residents of City 17 learn to live under the rule of their invaders. But among this scattered population are two of Earth's most resourceful scientists: Dr. Eli Vance and his daughter Alyx, the founders of a fledgling resistance.

You and your father were relocated to City 17. In the years since, you've continued your clandestine scientific activity—performing critical research, and building invaluable tools for the few humans brave enough to defy the Combine.
Every day you learn more about your enemy, and every day you work toward finding a weakness.

Lean around a broken wall and under a barnacle to make an impossible shot. Rummage through shelves to find a healing syringe and some shotgun shells. Manipulate tools to hack alien interfaces. Tear a headcrab off your face and throw it out the window. VR was built for the kind of gameplay that sits at the heart of Half-Life.
Half-Life: Alyx supports a variety of play environments, locomotion methods, and input devices.

If you have VR hardware that works with a computer, then it works with SteamVR.
If you don’t yet own any VR hardware, now's the time. Headsets support different sets of features, so the experience will vary between them. Half-Life: Alyx was built hand in hand with Valve Index, which is the highest fidelity option on the market, but the game works great with Vive, Rift and Windows Mixed Reality too. Check out the different options to choose which one is right for you.

Appears in your Steam Library

There's no need to enter a key or purchase the game. It just appears in your Steam Library.

…No matter when you bought your gear

Half-Life: Alyx is yours, whether you've had your Valve Index for a while, or are just about to take the plunge.

…Or whether you have the whole VR kit

Half Life Rtx

Owners of Valve Index controllers also get Half-Life: Alyx for free.

A set of Source 2 tools for building new levels is included with the game, enabling any player to build and contribute new environments for the community to enjoy. Hammer, Valve’s level authoring tool, has been updated with all of the game's virtual reality gameplay tools and components.

The Half-Life Alyx Soundtrack will be released in a chronological fashion following the chapters of the game. While chapters are being published, the soundtrack will be available for streaming on Spotify and Apple Music, and for download on Steam Music. Once the entire soundtrack has been released, it will become available on all major music streaming and download platforms.

Half Life 2

Half-life Equation

Halflife2.net