Is Tramadol an Opioid? Effects, Risks, and Warnings

Tramadol is an opioid, though it behaves differently from the opioids most people picture when they hear that word. It binds to the same mu-opioid receptors that morphine and oxycodone target, but it also blocks the reuptake of serotonin and norepinephrine in the brain, giving it a dual mechanism that sets it apart from conventional painkillers. That hybrid identity has shaped almost everything about how tramadol is prescribed, regulated, and misunderstood.

How Tramadol Works in the Body

Tramadol itself actually has weak affinity for the mu-opioid receptor. Much of the opioid-style pain relief comes from a metabolite called O-desmethyltramadol, usually referred to as M1. Your liver produces M1 when it processes tramadol, and M1 binds to the mu-opioid receptor with far greater strength than the parent drug. One receptor-binding study found that M1’s affinity for the human mu-opioid receptor was roughly 700 times higher than tramadol’s own affinity.¹ That said, tramadol is not merely a prodrug waiting to become M1. Research in oocyte models has shown that tramadol itself can directly activate mu-opioid receptors, though at higher concentrations than M1.²

The second part of tramadol’s mechanism is what really distinguishes it. Tramadol inhibits the reuptake of serotonin and norepinephrine, two neurotransmitters involved in mood regulation and descending pain pathways. A positron emission tomography study in primates showed that tramadol occupied serotonin and norepinephrine transporters in a dose-dependent fashion, reaching occupancy levels as high as about 70% at adequate doses.³ This makes tramadol pharmacologically similar to certain antidepressants, and it explains many of the drug’s unusual side effects and interaction risks that pure opioids do not share.

Your Genetics Determine How Well It Works

Because tramadol depends so heavily on its M1 metabolite for opioid-style pain relief, and because the liver enzyme that produces M1 (CYP2D6) varies dramatically from person to person, two patients given the same dose can have very different experiences. People who carry gene variants that make them “poor metabolizers” of CYP2D6 produce much less M1 and tend to get less pain relief. Conversely, “ultrarapid metabolizers” convert tramadol to M1 faster and at higher levels, increasing the risk of side effects like respiratory depression. A study of post-surgical patients confirmed that poor and intermediate metabolizers had significantly lower M1 blood levels compared to normal and ultrarapid metabolizers at both 30 and 120 minutes after dosing.⁴

Roughly 5 to 10 percent of people of European descent are CYP2D6 poor metabolizers, and that fraction varies across populations. For these individuals, tramadol may be no more effective than a placebo for opioid-type pain relief, though the serotonin and norepinephrine effects still contribute some analgesia. Ultrarapid metabolizers, estimated at 1 to 2 percent of Europeans but up to about 30 percent in certain East African and Middle Eastern populations, face the opposite problem: the drug can be too potent. This is the same genetic variability that led the FDA to warn against giving codeine to children, since codeine is metabolized through the same enzyme pathway.⁵

How It Compares to Other Painkillers

Tramadol is frequently described as a “mild” opioid, but the clinical picture is more nuanced than that label suggests. For chronic conditions like osteoarthritis, controlled-release tramadol has been shown to provide pain relief and improvements in stiffness and physical function comparable to diclofenac, a common anti-inflammatory drug.⁶ Against stronger opioids like morphine or oxycodone, tramadol provides somewhat less raw pain reduction but is broadly considered comparable at appropriate doses.

Where the comparison gets interesting is when you stack tramadol against NSAIDs like ibuprofen or naproxen. A systematic review published in Canadian Family Physician found that tramadol (with or without acetaminophen) was actually less likely to achieve meaningful pain reduction than NSAIDs, while producing more adverse events and more treatment dropouts.⁷ That finding challenges the common clinical assumption that tramadol is a safer “step up” from over-the-counter anti-inflammatories. When compared head-to-head with other opioids in the same review, tramadol showed no significant difference in either pain relief or harm outcomes. In short, tramadol is not markedly gentler than full opioids in terms of side effects, and it is not clearly better than NSAIDs at relieving pain.

Its Regulatory Story

Tramadol was initially marketed in the United States in 1995 as an unscheduled prescription painkiller, meaning it was not classified as a controlled substance. The thinking at the time was that its dual mechanism and weaker opioid binding made it low-risk for abuse. That assessment held for nearly two decades. In 2014, the DEA placed tramadol into Schedule IV of the Controlled Substances Act, the same category as benzodiazepines and sleep medications like zolpidem.⁸ The reclassification was driven by accumulating evidence of misuse, dependence, and diversion. Several U.S. states had already individually scheduled tramadol before the federal rule caught up.

For context, Schedule IV is two tiers below the Schedule II classification given to drugs like oxycodone, morphine, and fentanyl. The lower scheduling reflects tramadol’s comparatively lower (but not absent) potential for abuse and dependence. In some countries outside the U.S., tramadol remains available without strict scheduling, which has contributed to widespread non-medical use in parts of Africa and the Middle East.

The Seizure Risk

Seizures are the most distinctive serious risk associated with tramadol, and one that separates it from other opioids. The mechanism appears unrelated to tramadol’s opioid activity. In animal studies, the standard opioid-reversal drug naloxone did not prevent tramadol-induced seizures, but diazepam (a benzodiazepine) abolished them completely.⁹ This strongly suggests the seizure risk comes from tramadol’s non-opioid pathways, likely its effects on serotonin and possibly other neurotransmitter systems.

The seizure risk climbs sharply with overdose and when tramadol is combined with certain other drugs. A study of older nursing home residents found that taking tramadol alongside antidepressants that inhibit the CYP2D6 enzyme was associated with a higher rate of seizures than tramadol paired with antidepressants that do not inhibit that enzyme.¹⁰ A 2025 case report and literature review reinforced that tramadol can lower the seizure threshold even at therapeutic doses, and called for greater awareness among prescribers.¹¹ People with epilepsy or a history of seizures are generally advised to avoid tramadol.

Serotonin Syndrome and Antidepressant Interactions

Because tramadol blocks serotonin reuptake, combining it with other serotonergic drugs creates a real risk of serotonin syndrome, a condition marked by agitation, muscle twitching, rapid heart rate, high blood pressure, and in severe cases, dangerously high body temperature. The drugs most commonly involved in this interaction are SSRIs and SNRIs, the two most widely prescribed classes of antidepressants. The incidence of full-blown serotonin syndrome with the combination is low, and most cases are mild to moderate, but it can be life-threatening.¹²

Both seizures and serotonin syndrome are more likely to occur during misuse, overdose, or co-administration with antidepressants than during routine tramadol use alone.¹³ Given how many people take antidepressants, this interaction matters practically. If you are prescribed tramadol and are already on an SSRI, SNRI, or tricyclic antidepressant, the combination warrants a careful conversation with your prescriber about whether the risk is worth it.

A Side Effect Most People Do Not Expect

Tramadol can cause drops in blood sugar. This is unusual for an opioid and not widely appreciated by patients or even some physicians. A pharmacovigilance study comparing tramadol to codeine found a significantly higher rate of hypoglycemia reports associated with tramadol, both in people taking diabetes medications and in those who were not.¹⁴ A separate analysis using the FDA’s adverse event reporting database found that tramadol’s association with hypoglycemia was dramatically higher than for the broader opioid class and could not be explained by its serotonin or NMDA receptor effects.¹⁵

For most healthy people, this effect is unlikely to cause serious harm. But for people with diabetes, especially those on insulin or sulfonylureas, the added blood sugar-lowering effect of tramadol could push glucose levels to dangerous lows. Symptoms of hypoglycemia like shakiness, sweating, and confusion can also be mistaken for side effects of the drug itself, so the condition might go unrecognized.

Abuse Potential and Dependence

Tramadol’s abuse potential exists, but it looks different from that of classic opioids. A systematic review of laboratory studies found that tramadol’s relative abuse potential was lower than the opioids it was compared against. Participants given tramadol generally reported more negative effects at higher doses, experienced a slower onset, and were less likely to identify it as an opioid. Interestingly, the abuse potential appeared highest when tramadol was taken by mouth by people who were not already dependent on opioids.¹⁶ An older comparison study similarly found that at moderate injectable doses, tramadol was essentially indistinguishable from placebo in experienced opioid users, while morphine produced characteristic euphoria and pupil constriction.¹⁷

These laboratory findings help explain why tramadol was initially sold without controls, but they should not be mistaken for proof that tramadol is safe from misuse. Real-world patterns tell a different story. In Africa, particularly in Egypt and Nigeria, non-medical use of tramadol has become a major public health problem, with the majority of research on the topic concentrated in those two countries.¹⁸ Iran has similarly documented widespread tramadol misuse.¹⁹ Much of this misuse occurs in settings where tramadol is easier to obtain than other opioids, where it is perceived as harmless, or where it is used for non-pain purposes like enhancing work endurance or sexual performance.

Withdrawal Is Not Straightforward

People who use tramadol regularly and then stop can experience withdrawal, and tramadol withdrawal has a character all its own. A surveillance project found that withdrawal symptoms accounted for nearly 40 percent of all adverse events reported with chronic tramadol use. Most cases involved classic opioid withdrawal symptoms like muscle aches, sweating, nausea, and restlessness. But roughly one in eight cases presented with atypical symptoms not normally seen in opioid withdrawal, including hallucinations, paranoia, extreme anxiety, panic attacks, confusion, and unusual sensory experiences like numbness or tingling.²⁰

These atypical symptoms are thought to arise from tramadol’s serotonergic and noradrenergic actions, not from its opioid properties. Case reports have documented frank psychosis during tramadol withdrawal, a presentation that would be extremely unusual in withdrawal from a pure opioid.²¹ This is relevant because the standard treatment for opioid withdrawal, tapering with methadone or buprenorphine, may not fully address tramadol’s atypical withdrawal features. Clinicians managing tramadol discontinuation sometimes need to treat what is, in effect, two overlapping withdrawal syndromes.

What Happens in Overdose

Tramadol overdose is more complex to manage than overdose from a conventional opioid. Naloxone, the rescue drug in every first-aid kit for opioid emergencies, does reverse tramadol-induced respiratory depression. However, animal research has shown that naloxone also significantly increased seizure activity in tramadol-overdosed rats and prolonged the duration of those seizures.²² The working theory is that by stripping away tramadol’s opioid-mediated sedation, naloxone unmasks the stimulant-like seizure-producing activity of tramadol’s non-opioid pathways. This does not mean naloxone should be withheld from someone who is not breathing after a tramadol overdose. Stopping respiratory failure is the priority. But emergency physicians need to be prepared for seizures, and the finding underscores how tramadol does not fit neatly into the playbook designed for pure opioids.

Tramadol Compared to Codeine

Tramadol and codeine are often lumped together as “weak opioids” on the WHO analgesic ladder, and they share CYP2D6-dependent metabolism. But a large observational study published in JAMA found that patients initially prescribed tramadol had a higher one-year rate of all-cause mortality, cardiovascular events, and fractures compared to those started on codeine.²³ The study found no significant difference between the two drugs in rates of falls, delirium, constipation, opioid abuse or dependence, or sleep disorders. These findings came from an observational design and cannot prove that tramadol directly caused the excess mortality, but they have contributed to a more cautious re-evaluation of the assumption that tramadol is inherently safer than codeine.

Pregnancy and Children

Tramadol crosses the placenta, and regular use during pregnancy can cause neonatal abstinence syndrome in the newborn, which involves withdrawal symptoms like irritability, feeding difficulties, tremors, and excessive crying.²⁴ A large study in JAMA Network Open found that the risk of neonatal opioid withdrawal syndrome with tramadol was statistically similar to hydrocodone, while stronger opioids like oxycodone, morphine, and methadone carried two- to three-fold higher risks.²⁵ That said, “similar risk to hydrocodone” is not the same as safe. Any opioid used chronically during pregnancy carries withdrawal risk for the newborn.

In children, the same CYP2D6 variability that creates uneven responses in adults is more dangerous. The FDA issued warnings against using codeine and tramadol in children under 12 for pain management, and against their use in adolescents after tonsillectomy or adenoidectomy, citing deaths and severe respiratory depression linked to ultrarapid metabolizer status.⁵

When Vets Prescribe It for Your Dog

Tramadol is one of the most commonly prescribed pain medications for dogs, but the evidence for whether it actually works well in canines is surprisingly thin. The problem traces back to the same M1 metabolite that is responsible for opioid-derived pain relief in humans. Dog livers produce M1 more slowly than human livers, and they are much faster at producing a different metabolite (M2) that has no meaningful opioid activity. One study of liver enzyme activity found that M1 formation from tramadol in dog liver was slower than in cat liver by nearly fourfold.²⁶ Pharmacokinetic work in dogs confirmed that while they do produce M1 after receiving tramadol intravenously, the circulating levels of M1 were lower than expected.²⁷

The clinical implication is uncertain. Tramadol may still help dogs through its serotonin and norepinephrine effects, and some veterinarians report subjective improvements in their patients. But the opioid component that accounts for a large share of tramadol’s pain relief in humans may contribute far less in dogs. This has led many veterinary pain specialists to move away from tramadol as a first-line analgesic for dogs, favoring NSAIDs or other options with better-documented efficacy in that species. Cats, on the other hand, appear to metabolize tramadol more similarly to humans and may benefit more reliably from the drug.