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Last reviewed on RxList: 7/16/2019
Ketek Side Effects Center

Last reviewed on RxList 7/16/2019

Ketek (telithromycin) is an antibiotic used to treat bacterial infections in the lungs and sinuses. Common side effects of Ketek include:

The dose of Ketek tablets is 800 mg (2 tablets of 400 mg) taken orally once every 24 hours, for 7–10 days. 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. During pregnancy, Ketek should be used only when prescribed. It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

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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Ketek Consumer Information
SIDE EFFECTS: Nausea, vomiting, mild diarrhea, headache, anxiety, or a strange taste in the mouth may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these unlikely but serious side effects occur: vision changes (e.g., blurred/double vision, difficulty focusing).

Seek immediate medical attention if any of these rare but serious side effects occur: dizziness, fainting, irregular/fast heartbeat, worsening muscle weakness.

Telithromycin may rarely cause very serious liver disease. Seek immediate medical attention if you develop: extreme tiredness, loss of appetite, stomach/abdominal pain, dark urine, yellowing eyes/skin.

This medication may rarely cause a severe intestinal condition (Clostridium difficile-associated diarrhea) due to resistant bacteria. This condition may occur weeks to months after treatment has stopped. Do not use anti-diarrhea products or narcotic pain medications if you have the following symptoms because these products may make them worse. Tell your doctor immediately if you develop persistent diarrhea, abdominal or stomach pain/cramping, or blood/mucus in your stool.

Use of this medication for prolonged or repeated periods may result in oral thrush or a new vaginal yeast infection (oral or vaginal fungal infection). Contact your doctor if you notice white patches in your mouth, a change in vaginal discharge, or other new symptoms.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any of the following symptoms of a serious allergic reaction: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the entire patient information overview for Ketek (Telithromycin)


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Ketek Professional Information


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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Read the Ketek User Reviews »

© 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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