Opioids and Benzodiazepines: Why the Combination Is So Dangerous

Opioids and benzodiazepines are two of the most commonly prescribed drug classes in the United States, and millions of people are prescribed both. In 2016 the U.S. Food and Drug Administration required its strongest warning, the boxed warning, on roughly 400 opioid and benzodiazepine products because of what happens when they are taken together. This page explains the biology behind that decision, and what it means for a person who is already taking both.

What Benzodiazepines Are and Who Takes Them

Benzodiazepines are central nervous system depressants prescribed for anxiety, panic disorder, insomnia, seizures, muscle spasm, and alcohol withdrawal. The most commonly encountered are alprazolam (Xanax), clonazepam (Klonopin), lorazepam (Ativan), diazepam (Valium), and temazepam (Restoril).

They differ from one another mainly in how quickly they take effect and how long they last. Alprazolam acts quickly and clears relatively quickly, which is part of why it produces noticeable rebound anxiety between doses. Diazepam and clonazepam persist far longer, and their active byproducts can accumulate over days, particularly in older adults. That accumulation matters for interaction risk, because a person can be carrying more of the drug than the timing of the last dose would suggest.

Benzodiazepines are genuinely useful medicines. They are also physically addictive, and the FDA updated the boxed warning on the entire class in 2020 to state more clearly that dependence and withdrawal can develop even at recommended doses.

Why the Combination Suppresses Breathing So Effectively

Breathing is controlled automatically by a network of neurons in the brainstem that responds to rising carbon dioxide in the blood. When carbon dioxide climbs, the network fires and the body takes a breath. It is one of the most protected reflexes in human physiology, and it is very difficult to override deliberately.

Opioids weaken it by binding mu-opioid receptors on those neurons, which makes them less responsive to carbon dioxide. The body still breathes, but it tolerates a higher carbon dioxide level before doing so.

Benzodiazepines weaken the same reflex from a different direction. They enhance the effect of GABA, the brain's principal inhibitory neurotransmitter, at GABA-A receptors. The result is broad suppression of neuronal activity, including in the regions that maintain arousal and respiratory drive.

The two effects converge on the same outcome by routes that do not compete with each other. Nothing in the opioid pathway limits the benzodiazepine effect, and nothing in the benzodiazepine pathway limits the opioid effect. In practice this means the combination often produces more respiratory depression than either drug would produce at an equivalent total dose.

Sedation is the visible signal that this is happening. A person becomes drowsy first, then difficult to rouse, and only then does breathing become obviously abnormal. By the point breathing looks wrong, the process is already well advanced. This is why unusual sleepiness after a dose change is treated as an emergency signal rather than an inconvenience.

What the FDA Boxed Warning Actually Says

On August 31, 2016, after reviewing studies showing rising co-prescription of the two classes alongside rising overdose deaths involving both, the FDA required a boxed warning on prescription opioid pain medicines, prescription opioid cough products, and benzodiazepines.

The warning describes the risks of combined use as extreme sleepiness, respiratory depression, coma, and death. The agency also required patient Medication Guides carrying the same information, so that the warning would reach the person taking the drug and not only the prescriber.

A boxed warning is the most serious warning the FDA issues. It does not prohibit the combination, and there are patients for whom both drugs are appropriate. What it signals is that the combination must be a deliberate clinical decision with monitoring attached, never an accident of two prescriptions that never met.

In 2020 the FDA went further with the benzodiazepine class itself, updating its boxed warning to address abuse, misuse, addiction, physical dependence, and withdrawal reactions, and noting that risks increase when benzodiazepines are combined with other medicines including opioid pain relievers.

How People End Up on Both Without Realizing the Risk

The people harmed by this combination are usually not misusing anything. Several ordinary paths lead to it.

Two prescribers, no shared record. A surgeon prescribes an opioid after a procedure. A primary care clinician or psychiatrist has been prescribing a benzodiazepine for months. Neither knows about the other, and the patient does not realize the two are related.

Pain and anxiety travel together. Chronic pain reliably produces anxiety and insomnia, and both are commonly treated pharmacologically. The clinical logic for each prescription is sound in isolation.

Different pharmacies. Interaction checking happens within a pharmacy system, not across all of them. Two pharmacies means neither has the full picture.

A borrowed pill. A person taking a prescribed opioid cannot sleep and takes a family member's alprazolam. This single decision accounts for a substantial number of emergency department visits.

Illicit supply. Counterfeit tablets sold as benzodiazepines increasingly contain novel synthetic benzodiazepines or fentanyl, sometimes both. A person believing they are taking one drug may be taking a combination they never chose.

Warning Signs of a Combined Overdose

Call 911 immediately if a person taking both drugs shows any of the following.

• Slow, shallow, irregular, or stopped breathing
• Loud or unusual snoring or gurgling, which often means the airway is partly obstructed
• Cannot be woken by shouting, shaking, or firm pressure on the breastbone
• Blue or gray coloring of the lips, fingertips, or the skin around the mouth
• Pinpoint pupils together with unresponsiveness
• Limp body, cold or clammy skin

Earlier and softer signs, which are the ones that allow intervention before an emergency, include confusion, slurred speech, unusual clumsiness, falling asleep mid-conversation, and daytime drowsiness that was not present before a dose change.

Why Naloxone Is Only Half an Answer

Naloxone displaces opioids from opioid receptors and can restore breathing within minutes. It is available over the counter, it is safe to give when in doubt, and it belongs in every home where opioids are present.

It does nothing at GABA-A receptors. In a combined overdose, naloxone removes the opioid contribution and leaves the benzodiazepine contribution entirely in place. The person may start breathing and remain deeply sedated, or may improve briefly and deteriorate again as naloxone wears off, which typically happens well before the opioid has cleared.

The reversal agent for benzodiazepines, flumazenil, is not a home medication and is used sparingly even in hospitals, because in a person who is physically dependent on benzodiazepines it can precipitate seizures.

The practical rule is simple. Give naloxone, call 911, stay with the person, and place them on their side if they are breathing but unresponsive.

Why Neither Drug Can Be Stopped Abruptly

Learning about this interaction often produces an urge to stop one drug immediately. That instinct can create a worse emergency than the interaction.

Benzodiazepine withdrawal can be fatal. Abrupt discontinuation after regular use can cause seizures, delirium, dangerous blood pressure changes, and psychosis. Unlike opioid withdrawal, benzodiazepine withdrawal is genuinely life threatening, and the taper is often measured in months rather than weeks.

Opioid withdrawal is rarely fatal but carries its own danger. The specific risk is what follows. Tolerance falls within days, and a person who returns to their previous dose after a break is at high risk of overdose at an amount they previously handled without difficulty. This pattern accounts for many deaths after detoxification, incarceration, or hospitalization.

Any change to either medication belongs in the hands of a clinician who can see the whole picture and adjust gradually.

The Special Case of Buprenorphine and Methadone

People receiving buprenorphine or methadone for opioid use disorder are sometimes told they must stop their benzodiazepine, or are refused treatment because they take one. The FDA has addressed this directly, advising that the combined use of these medicines with benzodiazepines does increase risk, but that the harm of untreated opioid addiction usually outweighs that risk, and that careful medication management can reduce it.

In other words, the correct response is closer monitoring, coordination between prescribers, and naloxone in the home. It is not the withdrawal of treatment that keeps a person alive.

This distinction is worth knowing, because a person turned away from treatment on these grounds may reasonably ask for a second opinion.

What to Ask a Prescriber or Pharmacist

• Do you know everything else I am taking, including what I get from other pharmacies?
• Is there a lower dose of either medication that would still work?
• Is there a non-benzodiazepine option for my anxiety or sleep that does not depress breathing?
• Should the two be taken at different times of day, and does the timing actually reduce risk?
• Do I have any lung condition, sleep apnea, or liver problem that raises my risk further?
• Can you prescribe or recommend naloxone, and can you show someone in my household how to use it?
• What should the people I live with watch for, and at what point should they call 911?

A pharmacist can answer most of these without an appointment and at no cost.

Frequently Asked Questions

Can I take a benzodiazepine and an opioid if I space them several hours apart?

Spacing helps less than most people expect. Longer acting benzodiazepines such as diazepam and clonazepam remain active in the body for many hours and their byproducts accumulate over days, so a dose taken in the morning can still be contributing at night. Extended release opioids behave the same way. Spacing does not remove the overlap, it only makes it harder to see.

Which benzodiazepine is safest to take with an opioid?

No benzodiazepine is established as safe in this combination, and none of them lack the boxed warning. Shorter acting agents at low doses are sometimes preferred by clinicians because the exposure window is narrower, but that is a matter of managing risk rather than eliminating it, and it is a judgment for the prescriber who knows the whole medication list.

Is the risk the same for someone with high opioid tolerance?

Tolerance to the pain relieving and sedating effects of opioids develops faster and further than tolerance to their effect on breathing, so a person with substantial tolerance is still vulnerable to respiratory depression. Tolerance to opioids also provides no protection at all against the benzodiazepine half of the combination.

What about Z-drugs like zolpidem, are they safer than benzodiazepines?

Zolpidem, eszopiclone, and zaleplon act on the same GABA-A receptor complex as benzodiazepines, just at a different site. They carry a similar concern in combination with opioids, and they are frequently perceived as milder because they are marketed for sleep rather than anxiety. That perception is not supported by their pharmacology.

Do these drugs have to be swallowed at the same time to be dangerous?

No. What matters is whether both are present in the body at meaningful levels at the same time, not whether they were taken in the same moment. Because both classes include agents that last many hours, overlap is common even when the doses are hours apart.

How is benzodiazepine dependence different from opioid dependence?

Both produce physical dependence, meaning the body adapts and reacts when the drug is removed. The difference lies in what withdrawal does. Opioid withdrawal is severe and exhausting but rarely fatal in an otherwise healthy person. Benzodiazepine withdrawal can produce seizures and delirium and can be fatal, which is why benzodiazepine tapers are slower and require closer supervision.

Where can I find help if I am dependent on both?

Dependence on both is common and is a recognized clinical situation with established approaches, though it requires a setting that can manage two withdrawal processes at once rather than one. The SAMHSA National Helpline, free and confidential at any hour, is 1-800-662-4357. Further educational information is available at getdetox.com and opioidtreatmentfinder.com.

Related Guides

• Opioid drug interactions: which combinations are dangerous and why
• Opioids and alcohol
• Opioids and gabapentin or pregabalin

Sources

• U.S. Food and Drug Administration, boxed warning requirement for opioid analgesics, opioid cough products, and benzodiazepines, August 31, 2016
• U.S. Food and Drug Administration, updated boxed warning for the benzodiazepine drug class, September 2020
• U.S. Food and Drug Administration, drug safety communication on buprenorphine and methadone used with benzodiazepines or other central nervous system depressants, 2017
• National Institute on Drug Abuse, opioids research topics
• Centers for Disease Control and Prevention, overdose prevention
• Substance Abuse and Mental Health Services Administration, National Helpline