Ketek Side Effects Center

Last updated on RxList: 8/9/2022
Ketek Side Effects Center

What Is Ketek?

Ketek (telithromycin) is an antibiotic used to treat bacterial infections in the lungs and sinuses.

What Are Side Effects of Ketek?

Common side effects of Ketek include:

Ketek may cause serious side effects including:

  • hives,
  • difficulty breathing,
  • swelling of your face, lips, tongue, or throat,
  • vision changes,
  • blurred vision,
  • double vision,
  • difficulty focusing your eyes,
  • dizziness,
  • fainting,
  • irregular or fast heartbeat,
  • worsening muscle weakness,
  • extreme tiredness,
  • loss of appetite,
  • stomach pain,
  • dark urine,
  • yellowing of your eyes or skin (jaundice), and
  • diarrhea (may occur weeks or months after treatment has stopped)

Get medical help right away, if you have any of the symptoms listed above.

Seek medical care or call 911 at once if you have the following serious side effects:

  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms such as fast, irregular, or pounding heartbeats; fluttering in your chest; shortness of breath; and sudden dizziness, lightheartedness, or passing out;
  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors.

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

Dosage for Ketek

The dose of Ketek tablets is 800 mg (2 tablets of 400 mg) taken orally once every 24 hours, for 7–10 days.

What Drugs, Substances, or Supplements Interact with Ketek?

Ketek may interact with blood thinners, cholesterol-lowering medicines, ergot medicines, sedatives, itraconazole, ketoconazole, heart rhythm medications, rifampin, seizure medications, metoprolol, tacrolimus, sirolimus, cyclosporine, or digoxin. Tell your doctor all medications and supplements you use.

Ketek During Pregnancy or Breastfeeding

During pregnancy, Ketek should be used only when prescribed. It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

Additional Information

Our Ketek (telithromycin) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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The following serious and otherwise important adverse drug reactions are discussed in greater detail in other sections of labeling:

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

In Phase 3 clinical trials, 4,780 patients (n=2702 in controlled trials) received oral dosages of KETEK 800 mg once daily for 5 days or 7 to 10 days. Note that treatment with KETEK for 5 days duration is not a recommended dosage regimen. [see DOSAGE AND ADMINISTRATION]

In the combined Phase 3 studies, discontinuation due to adverse reactions occurred in 4.4% of KETEKtreated patients and 4.3% of combined comparator-treated patients. Most discontinuations in the KETEK group were due to adverse reactions in the gastrointestinal body system, primarily diarrhea (0.9% for KETEK vs. 0.7% for comparators), and nausea (0.7% for KETEK vs. 0.5% for comparators).

Adverse reactions (ARs) occurring in clinical studies in 2% or more of KETEK patients are included below.

Table 1: Adverse Reactions Reported in 2% or more of Patients in Controlled Phase 3 Clinical Studies

Adverse Reaction * Percent Incidence
n= 2702
n= 2139
Diarrhea 10% 8%
Nausea 7% 4.1%
Dizziness (excl. vertigo) 2.8% 1.5%
Vomiting 2.4% 1.4%
*Based on a frequency of all and possibly related adverse reactions of 2% or more in KETEK or comparator groups.
†Includes comparators from all controlled Phase 3 studies.

Less Common Adverse Reactions

Frequency Of 0.2% Or More And Less Than 2%

The following adverse reactions were observed at a frequency of 0.2% or more and less than 2% in KETEK-treated patients in clinical studies.

Gastrointestinal system: abdominal distension, dyspepsia, gastrointestinal upset, flatulence, constipation, gastroenteritis, gastritis, anorexia, oral candidiasis, glossitis, stomatitis.

Liver and biliary system: abnormal liver function tests: increased transaminases (i.e., ALT, AST). Hepatitis, with or without jaundice, occurred in 0.07% of patients treated with KETEK. [see WARNINGS AND PRECAUTIONS]

Nervous system: dry mouth, somnolence, insomnia, vertigo, increased sweating

Body as a whole: abdominal pain, fatigue

Special senses: Visual adverse reactions, some of them severe, most often included blurred vision, diplopia, or difficulty focusing. Some patients discontinued therapy due to these adverse reactions. Visual adverse reactions were reported as having occurred after any dose during treatment, but most (65%) occurred following the first or second dose. Visual adverse reactions lasted several hours and recurred upon subsequent dosing in some patients. For patients who continued treatment, some visual adverse reactions resolved on therapy while others persisted through the full course of treatment. [see WARNINGS AND PRECAUTIONS]

Females and patients under 40 years old experienced a higher incidence of KETEK-associated visual adverse reactions. Table 2 provides the incidence of all visual adverse reactions in controlled Phase 3 studies by age and gender. The group with the highest incidence was females under the age of 40, while males over the age of 40 had rates of visual adverse reactions similar to comparator-treated patients.

Table 2: Incidence of All Visual Adverse Reactions in Controlled Phase 3 Studies

Gender/Age Telithromycin Comparators*
Female 40 and under 2.1% (14/682) 0.0% (0/534)
Female greater than 40 1.0% (7/703) 0.35% (2/574)
Male 40 and under 1.2% (7/563) 0.48% (2/417)
Male greater than 40 0.27% (2/754) 0.33% (2/614)
Total 1.1% (30/2702) 0.28% (6/2139)
*Includes all comparators combined

Urogenital system: vaginal candidiasis, vaginitis, vaginosis fungal

Skin: rash

Hematologic: increased platelet count

Frequency of Less Than 0.2%

Other clinically-significant adverse reactions occurring in less than 0.2% of patients treated with KETEK from the controlled Phase 3 studies included: anxiety, bradycardia, eczema, elevated blood bilirubin, erythema multiforme, flushing, hypotension, increased blood alkaline phosphatase, increased eosinophil count, paresthesia, pruritus, urticaria.

Post-Marketing Experience

The following adverse reactions have been identified during post-approval use of KETEK. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Allergic: face edema, severe allergic (hypersensitivity) reactions, including angioedema and anaphylaxis

Cardiovascular: atrial arrhythmias, ventricular arrhythmias (including ventricular tachycardia and torsades de pointes) with potential fatal outcome, palpitation, ischemic cardiac events in the context of hypersensitivity reactions [see WARNINGS AND PRECAUTIONS]

Gastrointestinal system: pseudomembranous colitis, pancreatitis [see WARNINGS AND PRECAUTIONS]

Liver and biliary system: Hepatic dysfunction, fulminant hepatitis, hepatic necrosis, and hepatic failure, chromaturia [see CONTRAINDICATIONS; WARNINGS AND PRECAUTIONS]

Musculoskeletal: muscle cramps, arthralgia, myalgia, exacerbation of myasthenia gravis [see CONTRAINDICATIONS]

Nervous system: loss of consciousness, in some cases associated with vagal syndrome, tremor, convulsions

Psychiatric disorders: confusion, hallucinations (mostly visual)

Special senses: taste/smell perversion and/or loss, hearing loss

Respiratory, thoracic and mediastinal disorders: dyspnea

Read the entire FDA prescribing information for Ketek (Telithromycin)


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© Ketek Patient Information is supplied by Cerner Multum, Inc. and Ketek Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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