Eltrombopag Side Effects: Liver, Clots, and Eye Concerns

Eltrombopag is an oral medication that boosts platelet production, primarily prescribed for immune thrombocytopenia (ITP), aplastic anemia, and low platelets linked to chronic hepatitis C. Its most clinically watched side effects involve the liver, blood clots, and changes in the bone marrow, though everyday complaints like headache, nausea, and fatigue are more common. The drug carries a specific warning about liver damage, and the side-effect profile shifts depending on what condition you’re being treated for, how long you take it, and even your genetic background.

How the Drug Works and Why That Matters for Side Effects

Eltrombopag stimulates the body’s platelet-making machinery by mimicking a natural growth signal called thrombopoietin. It pushes early blood-forming cells in the bone marrow to mature into the cells that eventually release platelets into the bloodstream.¹ Understanding this mechanism explains several of the drug’s risks. If platelet counts climb too high, clotting risk goes up. Because the drug is processed through the liver, liver stress is a constant concern. And because it goads the bone marrow into sustained activity, prolonged use can change the marrow’s structure over time. Most of eltrombopag’s serious side effects trace back to one of those three pathways.

Liver Damage

Liver toxicity is the side effect that gets the most regulatory attention. Eltrombopag’s prescribing label includes a specific warning about the potential for serious liver injury, and routine blood tests to check liver enzymes are standard for anyone on the drug. In one study of 85 ITP patients treated with eltrombopag, liver dysfunction showed up in about one in five, mostly as mild elevations in liver enzymes or bilirubin. The majority of those cases were graded as mild, though a small fraction reached moderate severity.² A large pharmacovigilance study drawing on the FDA’s adverse event reporting database confirmed that eltrombopag carries stronger liver-related safety signals than some of its competitors in the same drug class.³

What makes some people more vulnerable? Recent research points to genetics. The way your body breaks down eltrombopag involves a liver enzyme called UGT1A1, and variations in the gene for that enzyme appear to influence how much of a potentially harmful byproduct accumulates. Researchers have suggested that monitoring levels of this byproduct and testing patients’ UGT1A1 genotype could help predict and prevent liver problems before they become serious.⁴ In practice, this kind of personalized screening isn’t yet routine, but it hints at where management of this side effect is heading. For now, the standard approach is checking liver function tests before starting treatment, every two weeks during dose adjustments, and monthly once stable.

In the large EXTEND study, which followed 302 ITP patients on eltrombopag for a median of about two and a half years, roughly 15% experienced some form of liver-related adverse event. The rate did not climb further after the first year of treatment, which is somewhat reassuring for long-term users.⁵

Blood Clots

Because eltrombopag raises platelet counts, there is an inherent tension at the heart of the treatment: too few platelets cause dangerous bleeding, but too many can trigger dangerous clotting. Thromboembolic events, meaning blood clots in veins or arteries, are an uncommon but serious risk. In the EXTEND study, about 6% of patients experienced a clot over the course of treatment, and this rate also did not increase beyond the first year.⁶

A systematic review and meta-analysis pooling data from 11 trials found that patients on drugs in this class experienced more clotting events than patients on placebo, though the difference did not reach statistical significance. The pooled risk ratio was about 1.8, meaning clots were roughly twice as frequent, but the confidence interval was wide enough to include the possibility of no real difference.⁷ The practical takeaway is that the absolute risk remains low, but it is real and not zero.

The types of clots reported cover a wide range. Case reports document deep vein thrombosis with pulmonary embolism in ITP patients on eltrombopag,⁸ cerebral venous thrombosis (a clot in the brain’s drainage veins) in a young woman just days after starting the drug,⁹ and portal vein thrombosis in a patient with underlying liver cirrhosis.¹⁰ That last case is worth flagging because patients with liver disease already face a higher baseline clotting risk in the portal vein system, and adding a platelet-boosting drug on top can tip the balance. If you have liver cirrhosis and are prescribed eltrombopag, your doctor should be monitoring especially closely for this complication.

Bone Marrow Changes

This one tends to surprise people. Because eltrombopag constantly stimulates the bone marrow to produce more platelets, prolonged use can cause the marrow to develop fibrous scar tissue, a condition called myelofibrosis. A long-term follow-up study of 66 ITP patients treated with drugs in this class found that roughly one in five developed moderate to severe marrow fibrosis after more than two years of treatment. Before treatment, two-thirds of biopsies showed no fibrosis at all; by the last biopsy, that proportion dropped to about one in five.¹¹

Individual case reports reinforce this pattern. One patient who had been on eltrombopag for three years developed significant marrow fibrosis, confirmed on biopsy as increased reticulin fiber deposition.¹² A scoping review of the literature confirmed that long-term eltrombopag use is associated with this kind of progressive marrow change.¹³

The clinical significance depends on severity. Mild fibrosis (grade 1) is common and often doesn’t affect blood counts or marrow function. Higher grades can impair the marrow’s ability to produce blood cells properly. Current guidelines recommend periodic bone marrow biopsies for patients on long-term treatment, though how often and at what intervals varies by institution. If significant fibrosis is found, the usual approach is to taper and discontinue the drug, which in many reported cases has led to partial or full reversal of the fibrosis over time.

Cataracts and Eye Concerns

Early animal studies raised an alarm when young rodents given high doses of eltrombopag developed cataracts. This triggered mandatory eye monitoring in clinical trials. The good news is that the human data has been reassuring. Across five clinical trials in chronic ITP patients, the rate of new cataracts or cataract progression was similar between eltrombopag and placebo groups. In the two short-term trials, about 5% of eltrombopag patients had cataract findings compared to 4% on placebo. In a longer trial, 8% of eltrombopag patients versus 10% of placebo patients had cataract changes. An expert committee reviewing the data concluded there was no evidence of a drug-related increase in cataract risk, noting that nearly all affected patients had prior corticosteroid use, which is itself a well-known cataract risk factor.¹⁴

That said, the prescribing information still recommends regular eye exams while on the drug. Since many ITP patients have been treated with corticosteroids at some point, distinguishing a steroid-related cataract from a drug-related one is difficult. The practical advice: get baseline eye exams and follow up regularly, but the cataract concern appears to be largely theoretical in humans at standard doses.

An interesting wrinkle from pediatric safety data involves a different eye finding. An analysis of the FDA’s adverse event reporting database found that vitreous opacities, which are floater-like changes in the gel filling the eye, showed the strongest safety signal among children taking eltrombopag.¹⁵ Whether this represents a real risk specific to children or a reporting artifact remains unclear, but it’s worth being aware of.

What Happens When You Stop

Eltrombopag doesn’t cure the underlying problem in most cases. It manages platelet counts while you take it. So stopping the drug means your platelet count will fall, and for some people, it falls hard. In a study of ITP patients who had responded to eltrombopag and then temporarily stopped, more than 80% relapsed, with a median time to relapse of just 15 days. Worse, 40% of those who relapsed experienced severe rebound thrombocytopenia, with platelet counts dropping below a dangerously low threshold.¹⁶

This rebound effect is a practical concern, not just a statistical one. If you need to stop eltrombopag for surgery, because of side effects, or for any other reason, the drop in platelets can happen fast enough to cause bleeding. The usual recommendation is to taper gradually rather than stop abruptly, and to monitor platelet counts closely during and after discontinuation.

Food, Antacids, and the Absorption Problem

Eltrombopag has one of the more demanding dosing schedules among oral medications. It binds aggressively to metal ions like calcium, iron, aluminum, and magnesium. If you take it with a meal, especially one high in dairy or calcium, or if you take it alongside a common antacid, the drug’s absorption drops dramatically. In a controlled study, a high-fat, high-calcium breakfast reduced blood levels of eltrombopag by about 59%. Taking the drug with a metal-containing antacid cut absorption by roughly 70%.¹⁷

In practice, this means you need to take eltrombopag on an empty stomach, at least one hour before or two hours after eating. Calcium-rich foods, dairy products, calcium-fortified juices, iron supplements, and antacids all need to be separated by at least four hours. Many patients find this scheduling difficult to maintain, and poor compliance with these restrictions is a real-world reason the drug sometimes seems to stop working when the issue is actually absorption, not resistance.

Differences Across Populations

Eltrombopag is processed differently depending on your ethnic background. A population pharmacokinetic analysis found that East Asian patients clear the drug about a third more slowly than patients of other backgrounds, leading to significantly higher drug exposure at the same dose. Female patients also showed somewhat higher levels than males. Because of these differences, prescribing guidelines recommend that East Asian patients start at a lower dose, typically 25 mg instead of the usual 50 mg.¹⁸ Higher drug exposure means a higher risk of dose-dependent side effects like liver damage, so this dosing adjustment isn’t trivial.

Safety in Children

Eltrombopag is approved for children with chronic ITP, and data from two major pediatric trials showed a favorable safety profile overall. The most common drug-related side effects in children were headache, nausea, and abnormal liver tests, the same pattern seen in adults.¹⁹ The most frequently reported adverse event in the FDA’s post-market database for children on eltrombopag was nosebleeds, which could reflect ongoing disease rather than a drug side effect, since nosebleeds are a hallmark of low platelet counts.²⁰

Long-term data in children remain limited, which is the honest caveat. The adult studies have not shown a clinically significant increase in clotting, marrow fibrosis, or cataracts, but whether those patterns hold over a child’s much longer expected treatment horizon is less certain.

Pregnancy and Eltrombopag

Eltrombopag is not routinely recommended during pregnancy. Animal studies showed embryo death and restricted fetal growth at high doses, and the drug crosses the placenta.²¹ A literature review of case reports found that while use during pregnancy appeared relatively safe in most reported cases, there was a possible association between eltrombopag used in the first or second trimester and lower birth weight, though this signal was muddied by the fact that most of these patients were also taking other drugs that could affect fetal growth.²²

In rare situations where a pregnant woman has severe, life-threatening thrombocytopenia that hasn’t responded to other treatments, some physicians have used eltrombopag as a last resort. At least one published case described a woman with aplastic anemia who took eltrombopag throughout pregnancy and delivered a healthy baby at term without the infant developing abnormal platelet counts afterward.²³ But isolated case reports are not a safety endorsement. The current consensus is that eltrombopag should be avoided in pregnancy unless the potential benefit clearly outweighs the risk and no safer alternative exists.

Clonal Evolution in Aplastic Anemia

Eltrombopag is also used in severe aplastic anemia, where it’s combined with immunosuppressive therapy to help kick-start blood cell production. In this setting, a different kind of risk has drawn attention: the possibility that the drug could drive abnormal genetic changes in blood-forming stem cells, potentially increasing the risk of evolving into a blood cancer like myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). Early data in patients with aplastic anemia that had come back after initial treatment showed a relatively high rate of these chromosomal abnormalities.²⁴

More reassuring data have followed. A phase 3 randomized trial comparing immunosuppressive therapy with and without eltrombopag in newly diagnosed aplastic anemia patients found that adding eltrombopag improved blood count recovery without increasing the rate of transformation to blood cancers.²⁵ A real-world analysis with longer follow-up found no cases of AML or MDS in either the eltrombopag-plus-immunosuppression group or the immunosuppression-alone group.²⁶ The current picture is cautiously optimistic: while clonal changes in the marrow can occur in aplastic anemia regardless of treatment, eltrombopag does not appear to make them significantly more likely.

The Long-Term Safety Picture

The EXTEND study is the largest and longest dataset we have on eltrombopag in ITP. In its final analysis, 302 patients were treated for a median of about 2.4 years, with some patients reaching nearly nine years of continuous use. About 14% withdrew because of adverse events. The individual reasons for withdrawal reflect the drug’s known risk areas: liver problems in seven patients, cataracts in four, deep vein thrombosis in three, strokes in two, headache in two, and marrow fibrosis in two. The reassuring finding was that rates of clotting events and liver problems did not accumulate over time, meaning the risk per year of treatment didn’t grow the longer you stayed on the drug.²⁷ An earlier interim analysis at the three-year mark had already found no new safety signals emerging with prolonged use.²⁸

One side-effect concern that the data have largely put to rest is the risk of the body forming antibodies against the drug itself. Because eltrombopag is a small synthetic molecule and does not resemble the body’s natural thrombopoietin protein, it is not expected to trigger an immune response that would neutralize either the drug or the body’s own thrombopoietin. This has been borne out clinically and represents a meaningful advantage over earlier experimental platelet-boosting agents that were abandoned precisely because of this problem.

Everyday Side Effects That Get Less Attention

The serious risks described above understandably dominate the conversation, but the side effects you’re most likely to actually feel day to day are more mundane. Headache is consistently the most commonly reported complaint in both adults and children. Upper respiratory infections, nausea, diarrhea, fatigue, and muscle aches are also common. In the EXTEND study, headache alone was enough to cause two patients to withdraw. Most people tolerate these symptoms without major disruption, but if headache or gastrointestinal symptoms are persistent or worsening, they’re worth reporting to your doctor, since they can occasionally signal rising drug levels or early liver stress rather than simple nuisance effects.

The fasting requirement discussed earlier adds its own burden. Taking a medication on an empty stomach once a day, then waiting before eating, is manageable but annoying enough that some people shift their dose to bedtime to simplify things. If you go this route, the same four-hour separation from calcium-rich foods and supplements still applies.