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Fostemsavir Side Effects

Medically reviewed by Last updated on Aug 3, 2020.

For the Consumer

Applies to fostemsavir: oral tablet extended release


Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • fast or pounding heartbeats, fluttering in your chest;

  • shortness of breath; and

  • sudden dizziness (like you might pass out).

Fostemsavir affects your immune system, which may cause certain side effects (even weeks or months after you've taken this medicine). Tell your doctor if you have:

  • signs of a new infection--fever, night sweats, swollen glands, cold sores, cough, wheezing, diarrhea, weight loss;

  • trouble speaking or swallowing, problems with balance or eye movement, weakness or prickly feeling; or

  • swelling in your neck or throat (enlarged thyroid), menstrual changes, impotence.

Nausea is the most common side effect of fostemsavir.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to fostemsavir: oral tablet extended release


Most (81%) of the side effects reported were of mild or moderate severity. This drug was discontinued due to a side effect in 7% of patients at week 96; the most common side effects leading to discontinuation were related to infections. Serious drug reactions were reported in 3% of patients and included a few cases of severe immune reconstitution inflammatory syndrome.[Ref]


Very common (10% or more): Elevated creatinine (19%)[Ref]

Elevated creatinine (greater than 1.8 times the upper limit of normal [1.8 x ULN] or 1.5 times baseline) has been reported in 19% of patients.

Clinically relevant increases in serum creatinine have been reported primarily in patients with identifiable risk factors for reduced renal function, including preexisting medical history of renal disease and/or concomitant agents known to increase creatinine; a causal association between this drug and elevated serum creatinine was not established.[Ref]


Very common (10% or more): Elevated direct bilirubin (up to 14%), elevated ALT (up to 14%), elevated AST (up to 14%)

Common (1% to 10%): Elevated bilirubin[Ref]

Elevated direct bilirubin (greater than ULN), ALT (greater than 5 x ULN), and AST (greater than 5 x ULN) have each been reported in up to 14% of patients; elevated bilirubin (at least 2.6 x ULN) has been reported in up to 6% of patients.

Increases in direct (conjugated) bilirubin have been reported after treatment with this drug. Clinically significant cases were uncommon and were confounded by intercurrent serious comorbid events (e.g., sepsis, cholangiocarcinoma, other complications of viral hepatitis coinfection); in the remaining cases, elevations in direct bilirubin (without clinical jaundice) were generally transient, occurred without increases in liver transaminases, and resolved on continued therapy.

Grade 3 and 4 elevations in ALT and AST have each been reported in 14% of patients with hepatitis B and/or C virus coinfection compared with 3% (ALT) and 2% (AST) of patients without viral hepatitis coinfection; in some cases, these transaminase elevations were consistent with hepatitis B reactivation, especially when antihepatitis therapy was stopped.[Ref]


Elevated lipase (greater than 3 x ULN) has been reported in up to 10% of patients.[Ref]

Common (1% to 10%): Nausea, elevated lipase, diarrhea, abdominal pain (included abdominal discomfort, abdominal pain, upper abdominal pain), dyspepsia, vomiting[Ref]


Elevated triglycerides (greater than 500 mg/dL), cholesterol (at least 300 mg/dL), and LDL cholesterol (at least 190 mg/dL) have been reported in up to 10%, 5%, and 4% of patients, respectively.[Ref]

Common (1% to 10%): Elevated triglycerides, fatigue (included fatigue, asthenia), elevated cholesterol, elevated low-density lipoprotein (LDL) cholesterol[Ref]


Common (1% to 10%): Decreased neutrophils, decreased hemoglobin, decreased leukocytes[Ref]

Decreased neutrophils (up to 599 cells/mm3) and hemoglobin (less than 9 g/dL) have been reported in up to 7% and 6% of patients, respectively.[Ref]

Nervous system

Common (1% to 10%): Headache, somnolence

Frequency not reported: Dizziness, dysgeusia, peripheral neuropathy (included peripheral neuropathy, peripheral sensory neuropathy)[Ref]


Hyperglycemia (greater than 250 mg/dL) and elevated urate (greater than 12 mg/dL) have been reported in 4% and 3% of patients, respectively.[Ref]

Common (1% to 10%): Hyperglycemia, elevated urate[Ref]


Common (1% to 10%): Sleep disturbance (included insomnia, sleep deficit, sleep disorder, abnormal dreams)[Ref]


Common (1% to 10%): Rash (included rash, generalized rash, maculopapular rash, pruritic rash, allergic dermatitis)

Frequency not reported: Pruritus[Ref]


Common (1% to 10%): Immune reconstitution inflammatory syndrome[Ref]


Elevated creatine kinase (at least 10 x ULN) has been reported in 2% of patients.[Ref]

Common (1% to 10%): Elevated creatine kinase

Frequency not reported: Myalgia[Ref]


Frequency not reported: Prolonged ECG QT[Ref]

All reports of prolonged ECG QT were asymptomatic.[Ref]


1. "Product Information. Rukobia (fostemsavir)." ViiV Healthcare, Research Triangle Park, NC.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.