May 5, 2016
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"Every year as many as 10 million U.S. children risk side effects from antibiotic prescriptions that are unlikely to help their upper respiratory conditions. Many of these infections are caused by viruses, which are not helped by antibiotics."...



Ketek Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 2/23/2016

Ketek (telithromycin) is an antibiotic used to treat bacterial infections in the lungs and sinuses. Common side effects of Ketek include nausea, vomiting, mild diarrhea, headache, anxiety, a strange taste in the mouth, or vaginal itching or discharge.

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.

What is Patient Information in Detail?

Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.

Ketek in Detail - Patient Information: Side Effects

Telithromycin may cause sudden and serious liver damage. In rare cases, liver failure can develop and may cause death. Stop using the medication and call your doctor right away if you have nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

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

Stop using telithromycin and call your doctor at once if you have a serious side effect such as:

  • diarrhea that is watery or bloody;
  • severe dizziness, fainting, fast or pounding heartbeats;
  • confusion, hallucinations; or
  • problems with vision (difficulty focusing, double vision).

Less serious side effects may include:

  • mild diarrhea;
  • mild nausea, vomiting;
  • vaginal itching or discharge; or
  • changes in your sense of taste.

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.

Read the entire detailed patient monograph for Ketek (Telithromycin)

What is Patient Information Overview?

A concise overview of the drug for the patient or caregiver from First DataBank.

Ketek Overview - Patient Information: Side Effects

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)

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Ketek FDA Prescribing Information: Side Effects
(Adverse Reactions)


In Phase III clinical trials, 4,780 patients (n=2702 in controlled trials) received daily oral doses of KETEK (telithromycin) 800 mg once daily for 5 days or 7 to 10 days. Most adverse events were mild to moderate in severity. In the combined Phase III studies, discontinuation due to treatment-emergent adverse events occurred in 4.4% of KETEK (telithromycin) -treated patients and 4.3% of combined comparator-treated patients. Most discontinuations in the KETEK (telithromycin) group were due to treatment-emergent adverse events in the gastrointestinal body system, primarily diarrhea (0.9% for KETEK (telithromycin) vs. 0.7% for comparators), nausea (0.7% for KETEK (telithromycin) vs. 0.5% for comparators).

All and possibly related treatment-emergent adverse events (TEAEs) occurring in controlled clinical studies in ≥ 2.0% of all patients are included below:

Table 5 : All and Possibly Related Treatment-Emergent Adverse Events Reported in Controlled Phase III Clinical Studies (Percent Incidence)

Adverse Event* All TEAEs Possibly-Related TEAEs
n= 2702
n= 2139
n= 2702
n= 2139
Diarrhea 10.8% 8.6% 10.0% 8.0%
Nausea 7.9% 4.6% 7.0% 4.1%
Headache 5.5% 5.8% 2.0% 2.5%
Dizziness (excl. vertigo) 3.7% 2.7% 2.8% 1.5%
Vomiting 2.9% 2.2% 2.4% 1.4%
Loose Stools 2.3% 1.5% 2.1% 1.4%
Dysgeusia 1.6% 3.6% 1.5% 3.6%
*Based on a frequency of all and possibly related treatment-emergent adverse events of ≥ 2% in KETEK (telithromycin) or comparator groups.
†Includes comparators from all controlled Phase III studies.

The following events judged by investigators to be at least possibly drug related were observed infrequently ( ≥ 0.2% and < 2%), in KETEK (telithromycin) -treated patients in the controlled Phase III studies.

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

Liver and biliary system: abnormal liver function tests: increased transaminases, increased liver enzymes (e.g., ALT, AST) were usually asymptomatic and reversible. ALT elevations above 3 times the upper limit of normal were observed in 1.6%, and 1.7% of patients treated with KETEK (telithromycin) and comparators, respectively. Hepatitis, with or without jaundice, occurred in 0.07% of patients treated with KETEK, and was reversible. (See PRECAUTIONS, General.)

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

Body as a whole: abdominal pain, upper abdominal pain, fatigue

Special senses: Visual adverse events most often included blurred vision, diplopia, or difficulty focusing. Most events were mild to moderate; however, severe cases have been reported. Some patients discontinued therapy due to these adverse events. Visual adverse events were reported as having occurred after any dose during treatment, but most visual adverse events (65%) occurred following the first or second dose. Visual events lasted several hours and recurred upon subsequent dosing in some patients. For patients who continued treatment, some resolved on therapy while others continued to have symptoms until they completed the full course of treatment. (See WARNINGS and PATIENT INFORMATION.)

Females and patients under 40 years old experienced a higher incidence of telithromycinassociated visual adverse events. (See Clinical Studies.)

Urogenital system: vaginal candidiasis, vaginitis, vaginosis fungal

Skin: rash

Hematologic: increased platelet count

Other possibly related clinically-relevant events occurring in < 0.2% of patients treated with KETEK (telithromycin) from the controlled Phase III studies included: anxiety, bradycardia, eczema, elevated blood bilirubin, erythema multiforme, flushing, hypotension, increased blood alkaline phosphatase, increased eosinophil count, paresthesia, pruritus, urticaria.

Post-Marketing Adverse Event Reports

In addition to adverse events reported from clinical trials, the following events have been reported from worldwide post-marketing experience with KETEK (telithromycin) .

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

Cardiovascular: atrial arrhythmias, palpitations

Gastrointestinal system: pancreatitis

Liver and biliary system: Hepatic dysfunction has been reported.

Severe and in some cases fatal hepatotoxicity, including fulminant hepatitis, hepatic necrosis and hepatic failure have been reported in patients treated with KETEK (telithromycin) . These hepatic reactions were observed during or immediately after treatment. In some of these cases, liver injury progressed rapidly and occurred after administration of only a few doses of KETEK. (See CONTRAINDICATIONS and WARNINGS.) Severe reactions, in some but not all cases, have been associated with serious underlying diseases or concomitant medications.

Data from post-marketing reports and clinical trials show that most cases of hepatic dysfunction were mild to moderate. (See PRECAUTIONS, General.)

Musculoskeletal: muscle cramps, rare reports of exacerbation of myasthenia gravis. (See CONTRAINDICATIONS.) arthralgia, myalgia

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

Psychiatric disorders: confusion, hallucinations (mostly visual)

Special senses: taste/smell perversion and/or loss

Read the entire FDA prescribing information for Ketek (Telithromycin)

Ketek - User Reviews

Ketek User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Ketek sorted by most helpful. Patient Discussions FAQs

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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