How Does Xanax Work in the Body?

Most people who take Xanax know what it does: it calms them down. Fewer know How Does Xanax Work and how it does that. The “how” explains most of the warnings on the label, including why alprazolam makes you sleepy and why it shouldn’t be stopped abruptly.

GABA, the Brain’s Brake Pedal

Nerve cells pass signals to each other using chemical messengers. Some messengers rev nerve cells up. Others slow them down.

GABA, short for gamma-aminobutyric acid, is the brain’s main slowing-down messenger. When it binds to a nerve cell, that cell becomes less likely to fire.

A healthy brain keeps these signals in rough balance. In anxiety and panic, the circuits that handle fear and alertness can run hot, and the brakes don’t always keep up.

What Alprazolam Does at the Receptor

One of GABA’s main targets is the GABA-A receptor, a tiny channel in the outer wall of a nerve cell. When GABA binds to it, the channel opens and lets chloride ions flow in. Chloride carries a negative charge, and a cell with more of it inside is harder to set off.

Alprazolam binds to a different spot on the same receptor, called the benzodiazepine site. It can’t open the channel on its own. It changes the receptor’s shape so GABA works better, and the channel opens more often whenever GABA arrives. Pharmacologists call this positive allosteric modulation, a long way of saying it strengthens a signal the brain already sends.

Think of a volume knob. Alprazolam turns up the calming signal your brain is already producing.

Why You Feel Calm and Sleepy at the Same Time

GABA-A receptors aren’t limited to the parts of the brain that deal with fear. They’re found throughout it, including areas that control wakefulness, movement and memory. Strengthening GABA’s effect everywhere does more than ease worry.

Most of alprazolam’s side effects come from this:

• Sleepiness: the same quieting effect acting on the brain’s wakefulness systems.
• Clumsiness and slower reactions: its effect on movement and coordination.
• Trouble forming new memories: its effect on memory circuits, more noticeable at higher doses.
• Muscle relaxation: a mild relaxing effect on muscles.
• Fewer seizures: it makes seizures less likely, which matters when we get to withdrawal.

Our guide to Xanax side effects covers these in more detail.

From Tablet to Bloodstream

Immediate-release alprazolam is absorbed well from the digestive tract. Blood levels usually peak about one to two hours after a dose, and many people notice an effect before that.

From the bloodstream, it spreads through the body and crosses into the brain. A large share of it travels bound to proteins in the blood. The unbound portion is what’s free to act on receptors.

How the Liver Breaks It Down

Alprazolam is broken down mostly in the liver by an enzyme called CYP3A4. Its breakdown products, including one called alpha-hydroxyalprazolam, add little to the overall effect at usual levels. The kidneys then remove the drug and its breakdown products in urine.

CYP3A4 explains several of alprazolam’s drug interactions:

• Drugs that block the enzyme leave alprazolam in the body longer and at higher levels. Two antifungals, ketoconazole and itraconazole, block it strongly enough that they’re contraindicated with alprazolam.
• Drugs that speed the enzyme up, such as carbamazepine, can lower alprazolam levels and make it work less well.

A pharmacist can check your list for these. See Xanax drug interactions for more.

Half-Life, and Why the Feeling Fades First

Half-life is the time it takes for the amount of a drug in your blood to drop by half. For alprazolam in healthy adults, it averages about 11 hours, with a wide range from person to person. It tends to be longer in:

• older adults
• people with liver disease
• people with obesity

It takes several half-lives for a drug to be mostly cleared.

The calm you notice after an immediate-release dose usually wears off long before that. Once the level in the brain falls below a certain point, you stop feeling much, even though some alprazolam is still circulating. That leftover drug can still add to anything sedating you take later in the day, and it’s part of the reason some people feel slow the next morning. For timelines, see how long Xanax lasts and how long alprazolam stays in your system.

Immediate-Release vs. Extended-Release

Both versions contain alprazolam and act on the same receptors. They differ in how fast the drug reaches your blood. Immediate-release tablets rise and fall more quickly. Extended-release (XR) tablets let the drug out gradually, so levels stay steadier through the day.

One can’t be substituted for the other without your prescriber deciding to. XR tablets also have to be swallowed whole. Crushing, chewing or splitting them breaks the slow-release design and can release too much of the drug at once.

How the Brain Adapts Over Time

When alprazolam is taken regularly, the brain starts adjusting to the extra GABA activity. Receptors and the systems around them change in ways that push back against the drug.

That adjustment can lead to two things:

• Tolerance: some effects, especially sleepiness, may get weaker over time.
• Physical dependence: the brain comes to rely on the drug to stay balanced. This can happen even when every dose is taken exactly as prescribed.

If alprazolam is stopped suddenly or the dose drops fast, its calming influence disappears before the brain has time to readjust. What’s left is a nervous system running on the high side. That can show up as anxiety, poor sleep, irritability, shakiness and, in some cases, seizures. Alprazolam helps hold seizures back, so removing it abruptly takes that protection away too.

Dependence and addiction are different things. Addiction means compulsive use despite harm. Both can happen with benzodiazepines. Either way, any plan to reduce or stop alprazolam should come from your prescriber. Our article on Xanax withdrawal explains what that process looks like.

Why Alcohol and Opioids Are a Problem

Alcohol also acts on GABA-A receptors, at a different site. Combined with alprazolam, the effects pile up. Sedation gets heavier, coordination gets worse, and breathing can slow.

Opioids work through their own receptors, and one thing they do is weaken the brain’s drive to breathe. Add alprazolam’s sedation on top of that and the combination can lead to profound sedation, stopped breathing, coma or death. That danger is why the FDA requires a boxed warning about taking benzodiazepines with opioids.

Sleep aids, some antihistamines and muscle relaxants can add to the effect as well, so have a pharmacist look over everything you take. More in Xanax and alcohol.

What Alprazolam Can’t Do

Alprazolam lowers how strongly your brain reacts to anxiety. It doesn’t change the thought patterns, stress or biology behind an anxiety disorder, and when a dose wears off, symptoms can come back. That’s why prescribers often weigh it against, or pair it with, longer-term options such as certain antidepressants and therapy. Our complete guide to Xanax covers how it fits into anxiety treatment.

Frequently Asked Questions

What does Xanax do to your brain?

It makes GABA-A receptors respond more strongly to GABA, the brain’s main calming messenger. Nerve activity slows, which eases anxiety and also causes drowsiness.

Does Xanax increase GABA levels?

No. Alprazolam doesn’t add GABA. It strengthens the effect of the GABA your brain already makes.

Why does Xanax make me tired?

GABA-A receptors are spread across the brain, including areas that keep you awake and alert. When alprazolam boosts their activity, sleepiness comes along with the calm.

Is Xanax processed by the liver?

Yes, mainly by the CYP3A4 enzyme. Liver problems and some other medicines can change how much alprazolam ends up in your blood.

Why can’t you stop Xanax suddenly?

After regular use, the brain adjusts to having the drug there. Taking it away abruptly can cause withdrawal, which can be serious. Your prescriber can plan a gradual reduction.

The Bottom Line

Alprazolam strengthens GABA, your brain’s own calming signal. That one action accounts for both the relief and the side effects. It also explains why alcohol and opioids are risky with it, and why the brain can become dependent over time.

If you’d like help understanding how alprazolam fits with the rest of your medicines, visit our pharmacy or speak with our pharmacist.

References

• U.S. Food and Drug Administration. Xanax (alprazolam) tablets, prescribing information: Clinical Pharmacology and Drug Interactions sections. DailyMed.
• U.S. Food and Drug Administration. Xanax XR (alprazolam) extended-release tablets, prescribing information. DailyMed.
• FDA Drug Safety Communications on benzodiazepines (2020) and on opioid and benzodiazepine combined use (2016).
• MedlinePlus. Alprazolam.
• StatPearls (NCBI Bookshelf). Alprazolam; Benzodiazepines.
• National Institute of Mental Health. Anxiety Disorders.