Tramadol


Tramadol, sold under the brand name Tramal among others, is an opioid pain medication and a serotonin–norepinephrine reuptake inhibitor used to treat moderate to severe pain. When taken by mouth in an immediate-release formulation, the onset of pain relief usually begins within an hour. It is also available by injection. It is available in combination with paracetamol.
As is typical of opioids, common side effects include constipation, itchiness, and nausea. Serious side effects may include hallucinations, seizures, increased risk of serotonin syndrome, decreased alertness, and drug addiction. A change in dosage may be recommended in those with kidney or liver problems. It is not recommended in those who are at risk of suicide or in those who are pregnant. While not recommended in women who are breastfeeding, those who take a single dose should not generally have to stop breastfeeding. Tramadol is converted in the liver to O-desmethyltramadol, an opioid with a stronger affinity for the μ-opioid receptor.
Tramadol was patented in 1972 and launched under the brand name Tramal in 1977 by the West German pharmaceutical company Grünenthal GmbH. In the mid-1990s, it was approved in the United Kingdom and the United States. It is available as a generic medication and marketed under many brand names worldwide. In 2023, it was the 36th most commonly prescribed medication in the United States, with more than 16million prescriptions.

Medical uses

Pain relief

Tramadol is used primarily to treat mild to severe pain, both acute and chronic. There is moderate evidence for use as a second-line treatment for fibromyalgia, but it is not FDA-approved for this use. Its use is approved for treatment of fibromyalgia as a secondary painkiller by the NHS.
Its analgesic effects take approximately an hour to be realized, and it takes from two to four hours to reach peak effect after oral administration with an immediate-release formulation. On a dose-by-dose basis, tramadol has about one-tenth the potency of morphine and is practically equally potent when compared with pethidine and codeine. For moderate pain, its effectiveness is roughly equivalent to that of codeine in low doses and hydrocodone at very high doses. For severe pain, it is less effective than morphine.
Pain-reducing effects last approximately six hours. The potency of analgesia varies considerably as it depends on an individual's genetics. People with specific variants of CYP2D6 enzymes may not produce adequate amounts of the active metabolite for effective pain control.

Off-label uses

Restless legs syndrome

Sleep medicine physicians sometimes prescribe tramadol for refractory restless legs syndrome ; that is, RLS that does not respond adequately to treatment with first-line medications such as dopamine agonists or gabapentinoids, often due to augmentation.

Premature ejaculation

Tramadol, due to its activity as a serotonin reuptake inhibitor, is effective in the treatment of premature ejaculation per systematic reviews and meta-analyses and is used off-label for this indication. However, the British Society for Sexual Medicine 2025 guidelines recommend against use of tramadol for premature ejaculation due to recent reports of habituation.

Contraindications

Pregnancy and lactation

Use of tramadol during pregnancy is generally avoided, as it may cause some reversible withdrawal effects in the newborn. A small prospective study in France found, while an increased risk of miscarriages existed, no major malformations were reported in the newborn. Its use during lactation is also generally advised against, but a small trial found that infants breastfed by mothers taking tramadol were exposed to about 2.88% of the dose the mothers were taking. No evidence of this dose harming the newborn was seen.

Labor and delivery

Its use as an analgesic during labor is not advised due to its long onset of action. The ratio of the mean concentration of the drug in the fetus compared to that of the mother when it is given intramuscularly for labor pains has been estimated to be 1:94.

Children

Its use in children is generally advised against, although it may be done under the supervision of a specialist. On 21 September 2015, the FDA started investigating the safety of tramadol in use in persons under the age of 17. The investigation was initiated because some of these people have experienced slowed or difficult breathing. The FDA lists age under 12 years old as a contraindication.

Elderly

The risk of opioid-related adverse effects such as respiratory depression, falls, cognitive impairment, and sedation is increased. Tramadol may interact with other medications and increase the risk for adverse events.

Liver and kidney failure

The drug should be used with caution in those with liver or kidney failure, due to metabolism in the liver and elimination by the kidneys.

Side effects

The most common adverse effects of tramadol include nausea, dizziness, dry mouth, indigestion, abdominal pain, vertigo, vomiting, constipation, drowsiness, and headache. Other side effects may result from interactions with other medications. Tramadol has the same dose-dependent adverse effects as morphine including respiratory depression.

Dependence and withdrawal

Long-term use of high doses of tramadol causes physical dependence and withdrawal syndrome. These include both symptoms typical of opioid withdrawal and those associated with serotonin–norepinephrine reuptake inhibitor withdrawal; symptoms include numbness, tingling, paresthesia, and tinnitus. Psychiatric symptoms may include hallucinations, paranoia, extreme anxiety, panic attacks, and confusion. In most cases, tramadol withdrawal will set in 12–20 hours after the last dose, but this can vary. Tramadol withdrawal typically lasts longer than that of other opioids. Seven days or more of acute withdrawal symptoms can occur as opposed to typically 3 or 4 days for other codeine analogs.

Overdose

The clinical presentation in overdose cases can vary but typically includes neurological, cardiovascular, and gastrointestinal manifestations. The predominant neurological symptoms are seizures and altered levels of consciousness, ranging from somnolence to coma. Seizures are particularly notable due to tramadol's lowering of the seizure threshold, occurring in approximately half of acute poisoning cases. Patients often exhibit tachycardia and mild hypertension. Gastrointestinal disturbances such as nausea and vomiting are common, and agitation, anxiety, and cold and clammy skin may also be present.
While less common, severe complications like respiratory depression and serotonin syndrome can occur, particularly in polydrug overdoses involving other CNS depressants and agents with serotonergic activity. Additionally, individuals with genetic variations leading to CYP2D6 enzyme duplication may have an increased risk of adverse effects, due to faster conversion of tramadol to its active metabolite.
Acute tramadol overdose is generally not life-threatening, with most fatalities resulting from polysubstance overdose. Management includes cardiovascular monitoring, activated charcoal administration, hydration, and treatment of seizures. Naloxone, an opioid antagonist, can partially reverse some effects of tramadol overdose, particularly respiratory depression. However, its use may increase the risk of seizures due to unopposed alpha-adrenergic stimulation. For suspected serotonin syndrome, cyproheptadine, a serotonin antagonist, is considered an effective antidote.
The incidence of tramadol-related overdose deaths has been on the rise in certain regions. For instance, Northern Ireland has reported an increased frequency of such cases. In 2013, England and Wales recorded 254 tramadol-related deaths, while Florida reported 379 cases in 2011. In 2011, 21,649 emergency room visits in the United States were related to tramadol. The likely explanation for these observations is due to increase in frequency of prescriptions and use due to easier access due to lighter regulatory scheduling by authorities but this is starting to change. In 2021, Health Canada announced tramadol would be added to Schedule I of the Controlled Drugs and Substances Act and to the Narcotic Control Regulations due to tramadol being suspected of having contributed to 18 reported deaths in Canada between 2006 and 2017.

Interactions

Tramadol can have pharmacodynamic, pharmacokinetic, and pharmacogenetic interactions.
Tramadol is metabolized by CYP2D6 enzymes which contributes to the metabolism of approximately 25% of all medications. Any medications with the ability to inhibit or induce these enzymes may interact with tramadol. These include common antiarrhythmics, antiemetics, antidepressants, antipsychotics, analgesics, and tamoxifen.
Due to tramadol's serotonergic effects, tramadol has the potential to contribute to the development of an acute or chronic hyper-serotonin state called serotonin syndrome when used concurrently with other pro-serotonergic medications such as antidepressants, antipsychotics, triptans, cold medications containing dextromethorphan, and some herbal products such as St. John's wort.
Concurrent use of 5-HT3 antagonists such as ondansetron, dolasetron, and palonosetron may reduce the effectiveness of both drugs.
Tramadol also acts as an opioid agonist and thus can increase the risk for side effects when used with other opioid and opioid-containing analgesics.
Tramadol increases the risk for seizures by lowering the seizure threshold. Using other medications that lower seizure threshold - such as antipsychotic medications, bupropion, and amphetamines - can further increase this risk.

Pharmacology

Mechanism of action

Tramadol induces analgesic effects through a variety of different targets on the noradrenergic system, serotonergic system, and opioid receptors system. Tramadol affects serotonin and norepinephrine reuptake inhibition similarly to certain antidepressants known as serotonin–norepinephrine reuptake inhibitors, such as venlafaxine and duloxetine. Tramadol exists as a racemic mixture, the positive enantiomer inhibits serotonin reuptake while the negative enantiomer inhibits noradrenaline re-uptake, by binding to and blocking the transporters. Both enantiomers of tramadol are agonists of the μ-opioid receptor and its M1 metabolite, O-desmetramadol, is also a μ-opioid receptor agonist but is 6 times more potent than tramadol itself. All of these actions may work synergistically to induce analgesia.
Tramadol has been found to possess these actions:
Tramadol acts on the opioid receptors through its major active metabolite desmetramadol, which has as much as 700-fold higher affinity for the MOR relative to tramadol. Moreover, tramadol itself has been found to possess no efficacy in activating the MOR in functional activity assays, whereas desmetramadol activates the receptor with high intrinsic activity. As such, desmetramadol is exclusively responsible for the opioid effects of tramadol. Both tramadol and desmetramadol have pronounced selectivity for the MOR over the DOR and KOR in terms of binding affinity.
Tramadol is well-established as an SRI. In addition, a few studies have found that it also acts as a serotonin releasing agent, similar in effect to fenfluramine. The serotonin releasing effects of tramadol could be blocked by sufficiently high concentrations of the serotonin reuptake inhibitor 6-nitroquipazine, which is in accordance with other serotonin releasing agents such as fenfluramine and MDMA. However, two more recent studies failed to find a releasing effect of tramadol at respective concentrations up to 10 and 30 μM. In addition to serotonergic activity, tramadol is also a norepinephrine reuptake inhibitor. It is not a norepinephrine releasing agent. Tramadol does not inhibit the reuptake or induce the release of dopamine.
A positron emission tomography imaging study found that single oral 50-mg and 100-mg doses of tramadol to human volunteers resulted in 34.7% and 50.2% respective mean occupation of the serotonin transporter in the thalamus. The estimated median effective dose for SERT occupancy hence was 98.1 mg, which was associated with a plasma tramadol level of about 330 ng/mL. The estimated maximum daily dosage of tramadol of 400 mg would result in as much as 78.7% occupancy of the SERT. This is close to that of SSRIs, which occupy the SERT by 80% or more.
Peak plasma concentrations during treatment with clinical dosages of tramadol have generally been found to be in the range of 70 to 592 ng/mL for tramadol and 55 to 143 ng/mL for desmetramadol. The highest levels of tramadol were observed with the maximum oral daily dosage of 400 mg per day divided into one 100-mg dose every 6 hours. Some accumulation of tramadol occurs with chronic administration; peak plasma levels with the maximum oral daily dosage are about 16% higher and the area-under-the-curve levels 36% higher than following a single oral 100-mg dose. Positron emission tomography imaging studies have reportedly found that tramadol levels are at least four-fold higher in the brain than in plasma. Conversely, brain levels of desmetramadol "only slowly approach those in plasma". The plasma protein binding of tramadol is only 4–20%; hence, almost all tramadol in circulation is free, thus bioactive.