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Ketek Side Effects

Generic Name: telithromycin

Note: This page contains information about the side effects of telithromycin. Some of the dosage forms included on this document may not apply to the brand name Ketek.

In Summary

Common side effects of Ketek include: diarrhea. Other side effects include: headache and nausea. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to telithromycin: oral tablet

In addition to its needed effects, some unwanted effects may be caused by telithromycin (the active ingredient contained in Ketek). In the event that any of these side effects do occur, they may require medical attention.

Major Side Effects

You should check with your doctor immediately if any of these side effects occur when taking telithromycin:

  • Abdominal or stomach pain
  • blistering, peeling, or loosening of the skin
  • blurred vision
  • chest pain or discomfort
  • chills
  • confusion
  • convulsions
  • cough
  • dark urine
  • decreased urine
  • difficulty with breathing, chewing, swallowing, or talking
  • dizziness
  • double vision
  • drooping eyelids
  • dry mouth
  • fainting
  • faintness or lightheadedness when getting up suddenly from a lying or sitting position
  • fast, slow, or irregular heartbeat
  • fever with or without chills
  • increased thirst
  • itching
  • joint pain
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • light-colored stools
  • loss of appetite
  • mood changes
  • muscle pain or cramps
  • muscle weakness
  • nausea
  • nervousness
  • numbness or tingling in the hands, feet, or lips
  • red, irritated eyes
  • shortness of breath
  • skin rash
  • sores, ulcers, or white spots in the mouth or on the lips or tongue
  • stomach cramps, tenderness, or pain
  • sweating
  • tightness in the chest
  • unusual tiredness or weakness
  • upper right abdominal or stomach pain
  • vomiting
  • watery or bloody diarrhea
  • weakness or heaviness of the legs
  • wheezing
  • yellow eyes and skin
Incidence not known:
  • Black, tarry stools
  • clay-colored stools
  • continuous vomiting
  • dark-colored urine
  • decreased appetite
  • general feeling of tiredness or weakness
  • swelling of the feet or lower legs
  • unpleasant breath odor
  • vomiting of blood

Minor Side Effects

Some of the side effects that can occur with telithromycin may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common:
  • Diarrhea
Less common:
  • Abnormal dreams
  • acid or sour stomach
  • belching
  • bloated, full feeling, or pressure in the stomach
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • burning feeling in the chest or stomach
  • change in color, amount, or odor of vaginal discharge
  • change in sense of smell
  • change in taste
  • difficulty focusing the eyes
  • difficulty having a bowel movement (stool)
  • disturbed attention span
  • dry lips
  • dry skin
  • excess air or gas in the stomach or intestines
  • feeling of constant movement of self or surroundings
  • feeling of warmth, redness of the face, neck, arms, and occasionally, upper chest
  • frequent urination
  • headache
  • heartburn
  • increased amount of pale, dilute urine
  • indigestion
  • itching of the vagina or outside genitals
  • lack or loss of strength
  • lightheadedness
  • loose stools
  • loss of appetite
  • loss of sense of taste
  • pain during sexual intercourse
  • pain or tenderness around the eyes and cheekbones
  • passing gas more often than usual
  • redness of the skin
  • redness, swelling, or soreness of the tongue
  • sensation of spinning
  • shakiness in the legs, arms, hands, or feet
  • skin rash, encrusted, scaly, and oozing
  • sleeplessness
  • sore mouth or tongue
  • sore throat
  • stomach upset or pain
  • stuffy or runny nose
  • swelling or puffiness of the face
  • tenderness in the stomach area
  • thick, white curd-like vaginal discharge, without odor or with mild odor
  • tooth discoloration
  • trouble sleeping
  • weight loss
  • white patches in the mouth and on the tongue

For Healthcare Professionals

Applies to telithromycin: oral tablet


Severe liver injury and acute liver failure (in some cases fatal) have been reported. Such hepatic reactions were observed during or immediately after therapy and included fulminant hepatitis and hepatic necrosis leading to liver transplant. In some cases, liver injury progressed rapidly and occurred after a few doses of this drug were administered. Less severe liver dysfunction (associated with reversible hepatitis, elevated liver enzymes, and sometimes jaundice) has been reported.

Drug-related hepatotoxicity was reported in a 46-year-old man receiving treatment for an ear and sinus infection. The patient presented with a 4-day history of malaise, dark urine, jaundice, mild pruritus, and anorexia. The patient denied toxin exposure, IV drug abuse, or hepatic injury. ALT 948 units/L, AST 200 units/L, total bilirubin 65 mmol/L, and alkaline phosphatase 291 units/L were observed. These values warranted withdrawal of this drug and within 2 weeks the ALT decreased to 450 units/L and his jaundice resolved. After 8 weeks, the patient's liver tests had normalized.[Ref]

Common (1% to 10%): Increased liver enzymes (AST, ALT, alkaline phosphatase, GGT)
Uncommon (0.1% to 1%): Hepatitis (with or without jaundice)
Rare (0.01% to 0.1%): Cholestatic jaundice
Frequency not reported: Abnormal liver function tests, increased transaminases (ALT, AST), elevated blood bilirubin, increased ALT (at least 3 times the upper limit of normal), hepatocellular and/or cholestatic hepatitis (with or without jaundice), severe liver toxicity, hepatotoxicity (including acute liver failure, severe liver injury)
Postmarketing reports: Hepatic dysfunction, fulminant hepatitis, hepatic necrosis, hepatic failure, severe hepatitis[Ref]


Very common (10% or more): Diarrhea (10.8%)
Common (1% to 10%): Nausea, vomiting, gastrointestinal pain, flatulence
Uncommon (0.1% to 1%): Constipation, oral candidiasis, stomatitis
Very rare (less than 0.01%): Pseudomembranous colitis
Frequency not reported: Abdominal distension, dry mouth, dyspepsia, gastrointestinal upset, gastroenteritis, gastritis, glossitis, Clostridium difficile-associated diarrhea, loose stools, watery stools
Postmarketing reports: Pancreatitis[Ref]

Pseudomembranous colitis has also been reported during postmarketing experience.[Ref]

Nervous system

Exacerbations of myasthenia gravis (including fatal and life-threatening acute respiratory failure) have been reported. Rapid onset was observed in some cases, occurring within a few hours after the first dose.[Ref]

Common (1% to 10%): Headache, dizziness (excluding vertigo), taste disturbance/dysgeusia
Uncommon (0.1% to 1%): Somnolence, vertigo
Rare (0.01% to 0.1%): Paresthesia, transient loss of consciousness
Very rare (less than 0.01%): Parosmia
Postmarketing reports: Loss of consciousness (in some cases associated with vagal syndrome), exacerbation of myasthenia gravis, tremors, convulsions, taste/smell perversion, ageusia, anosmia, hearing loss[Ref]


Fatal and life-threatening acute respiratory failure has been reported in patients with myasthenia gravis.[Ref]

Frequency not reported: Acute respiratory failure, rhinitis, upper respiratory infection
Postmarketing reports: Dyspnea[Ref]


Common (1% to 10%): Vaginal candidiasis
Frequency not reported: Vaginitis, fungal vaginosis
Postmarketing reports: Chromaturia[Ref]


Uncommon (0.1% to 1%): Flush/flushing, palpitations
Rare (0.01% to 0.1%): Atrial arrhythmia, hypotension, bradycardia
Frequency not reported: Increased QTc interval
Postmarketing reports: QT/QTc interval prolongation, ventricular arrhythmias (including ventricular tachycardia, torsades de pointes) with potential fatal outcome, ischemic cardiac events (in the context of hypersensitivity reactions)[Ref]

Ventricular arrhythmias (including ventricular tachycardia, torsades de pointes) have sometimes occurred within a few hours after the first dose.

Atrial arrhythmias and palpitation have also been reported during postmarketing experience.[Ref]


Visual disturbances (some severe) most often included blurred vision, difficulty focusing, or diplopia; some patients stopped therapy due to these effects. Most visual side effects were reported after the first or second dose, lasted several hours, and recurred with subsequent doses in some patients. Symptoms continued throughout the entire course of therapy in some patients and resolved spontaneously during therapy in others. Females and patients up to 40 years of age had a higher rate of these side effects (females up to 40 years: 2.1%; females older than 40 years: 1%; males up to 40 years: 1.2%; males older than 40 years: 0.27%).[Ref]

Uncommon (0.1% to 1%): Blurred vision
Rare (0.01% to 0.1%): Diplopia
Frequency not reported: Visual disturbances (including blurred vision, difficulty focusing, diplopia)[Ref]


Uncommon (0.1% to 1%): Rash, pruritus, urticaria
Rare (0.01% to 0.1%): Eczema
Very rare (less than 0.01%): Erythema multiforme
Frequency not reported: Increased sweating
Postmarketing reports: Angioneurotic edema[Ref]


Uncommon (0.1% to 1%): Eosinophilia
Frequency not reported: Increased platelet count, increased eosinophil count[Ref]


Uncommon (0.1% to 1%): Anorexia
Frequency not reported: Increased blood alkaline phosphatase[Ref]


Uncommon (0.1% to 1%): Insomnia, nervousness
Frequency not reported: Anxiety
Postmarketing reports: Confusion, hallucinations (mostly visual)


Muscle cramps have also been reported during postmarketing experience.[Ref]

Very rare (less than 0.01%): Muscle cramps
Postmarketing reports: Arthralgia, myalgia[Ref]


Postmarketing reports: Severe allergic reactions (including angioedema, anaphylaxis), anaphylactic reactions (including anaphylactic shock), hypersensitivity[Ref]


Frequency not reported: Abdominal pain, fatigue, upper abdominal pain
Postmarketing reports: Face edema


1. Onur O, Guneysel O, Denizbasi A, Celikel C "Acute hepatitis attack after exposure to telithromycin." Clin Ther 29 (2007): 1725-1729

2. "Product Information. Ketek (telithromycin)." Aventis Pharmaceuticals, Bridgewater, NJ.

3. Clay KD, Hanson JS, Pope SD, Rissmiller RW, Purdum PP 3rd, Banks MD "Brief Communication: Severe hepatotoxicity of telithromycin: three case reports and literature review. Available from: URL:" ([2006 Mar 21]):

4. Clay KD, Hanson JS, Pope SD, Rissmiller RW, Purdum PP 3rd, Banks PM "Brief communication: severe hepatotoxicity of telithromycin: three case reports and literature review." Ann Intern Med 144 (2006): E1-E6

5. Owens RC Jr, Nolin TD "Antimicrobial-Associated QT Interval Prolongation: Pointes of Interest." Clin Infect Dis 43 (2006): 1603-1611

6. Nieman RB, Sharma K, Edelberg H, Caffe SE "Telithromycin and myasthenia gravis." Clin Infect Dis 37 (2003): 1579

Not all side effects for Ketek may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.