Linezolid belongs to the family of medications called antibiotics. It is used to kill certain types of bacteria that cause infections in the abdomen, lungs (e.g., pneumonia), urinary tract, skin, and skin-structures (e.g., sweat glands, hair follicles). This medication works by killing bacteria or preventing their growth.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The recommended dose of linezolid depends on the type of infection being treated. For uncomplicated skin and skin-structure infections, the dose is usually 400 mg every 12 hours for 10 to 14 days. For most other types of infections, the usual dose is 600 mg every 12 hours for 10 to 14 days or for 14 to 28 days (depending on the type of infection being treated). The tablets may be taken with or without food.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is very important to take this medication exactly as prescribed by your doctor. Finish all this medication, even if you have started to feel better.

If you miss a dose of this medication, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not use this medication if you:

• are allergic to linezolid or any ingredients of this medication
• have taken monoamine oxidase (MAO) inhibitors (e.g., phenelzine, tranylcypromine) in the past 2 weeks
• have uncontrolled high blood pressure
• have untreated thyroid disease
• have pheochromocytoma (tumour of the adrenal gland)
• are taking medications that increase blood pressure (e.g., pseudoephedrine, epinephrine, dopamine)
• are taking medications that affect the messenger serotonin (e.g., antidepressants, "triptan" migraine medications, buspirone, opioids)
• have carcinoid syndrome (a group of symptoms which results from the release of hormones, such as serotonin, from carcinoid tumours)

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• change in colour of tongue
• constipation
• diarrhea
• dizziness
• dry mouth
• headache
• increased thirst
• nausea
• rash
• stomach discomfort
• taste changes
• trouble sleeping
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• changes in vision (e.g., blurred vision, trouble seeing clearly)
• fever or chills
• increased blood pressure
• ringing in the ears

• signs of muscle damage (e.g., unexplained muscle pain, tenderness or weakness, brown or discoloured urine)

• symptoms of blood problems (unusual weakness or tiredness, unusual bleeding or bruising, shortness of breath, fever)
• symptoms of high blood sugar (e.g., frequent urination, increased thirst, excessive eating, unexplained weight loss, poor wound healing, infections, fruity breath odour)
• symptoms of low blood sugar (e.g., cold sweat, cool pale skin, headache, fast heartbeat, weakness)

• symptoms of low sodium levels in the blood (e.g., achy, stiff or uncoordinated muscles, confusion, tiredness, weakness)

• symptoms of nerve problems (numbness, tingling, prickling, or burning sensations)
• vaginal yeast infections (itching, white discharge)
• white patches in the mouth or on the tongue or throat

Stop taking the medication and seek immediate medical attention if any of the following occur:

• symptoms of antibiotic-associated diarrhea (severe, watery diarrhea that may be bloody)
• symptoms of a severe allergic reaction (hives, difficulty breathing, swelling of the mouth or throat)
• symptoms of a severe skin reaction such as blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort
• symptoms of lactic acidosis (severe or recurrent nausea, vomiting, or diarrhea)
• symptoms of serotonin syndrome (agitation, confusion, delirium, muscle stiffness, shaking, poor coordination, or seizures)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Antibiotic-associated diarrhea: This medication, like other antibiotics, may cause a potentially dangerous condition called antibiotic-associated, or pseudomembranous, colitis. Symptoms include severe, watery diarrhea that may be bloody. If you notice these symptoms, stop taking linezolid and contact your doctor as soon as possible.

Bacterial resistance: Misuse of an antibiotic such as linezolid may lead to the growth of resistant bacteria that will not be killed by the antibiotic. If this happens, the antibiotic may not work for you in the future. Although you may begin to feel better early in your course of treatment with linezolid, you need to take the full course exactly as directed to finish ridding your body of the infection and to prevent resistant bacteria from taking hold. Do not take linezolid or other antibiotics to treat a viral infection such as the common cold; antibiotics do not kill viruses, and using them to treat viral infections can lead to the growth of resistant bacteria.

Diabetes: Linezolid may cause a loss of blood glucose control and glucose tolerance may change. People with diabetes may find it necessary to monitor their blood sugar more frequently while using this medication. Symptoms of low blood sugar include lightheadedness, weakness, cool, pale skin, or rapid heart rate.

If you have diabetes, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Fluid and electrolyte balance: Linezolid may cause the levels of the electrolyte sodium in the blood to change while taking this medication. If you experience symptoms of fluid and electrolyte imbalance such as muscle pain or cramps; dry mouth; numb hands, feet, or lips; or racing heartbeat, contact your doctor as soon as possible. If you are taking this medication for longer than 2 weeks, your doctor may want you to have blood tests done to monitor the levels of these electrolytes in your blood while you are taking this medication.

Foods with high tyramine content: When using this medication, avoid large quantities of foods or beverages with high tyramine content (e.g., draft beers, red wines, soy sauce, aged cheeses). The combination of linezolid and large amounts of tyramine may result in episodes of dangerously high blood pressure, which can be life-threatening.

Kidney and liver function: People with decreased kidney or liver function may be more likely to experience decreased levels of platelets in the blood. As a result, this causes increased and unexpected bruising or bleeding.

If you have decreased kidney or liver function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Lactic acidosis: Rarely, linezolid may cause a serious condition called lactic acidosis (build-up of lactic acid in the blood). If you experience recurrent nausea or vomiting while taking this medication, get immediate medical attention.

Low blood cell counts: Linezolid may cause low blood cell counts. If you experience unusual weakness or tiredness, unusual bleeding or bruising, shortness of breath, or fever while taking linezolid contact your doctor immediately. Your doctor will monitor your blood cell counts while you are taking this medication.

Muscle effects: Muscle damage has been associated with the use of linezolid. Report any unexplained muscle pain, tenderness, weakness or cramps, or any brown or discoloured urine to your doctor immediately, particularly if you are also experiencing malaise (a general feeling of being unwell) or fever.

Nerve problems: Linezolid may cause a nerve problem called peripheral neuropathy, especially when used for longer than recommended. If you experience numbness, tingling or prickling sensations, or burning pain while taking this medication, contact your doctor.

Other medical conditions: Linezolid may cause symptoms of other illnesses to become worse. If you have uncontrolled high blood pressure, pheochromocytoma, carcinoid syndrome, or untreated overactive thyroid, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Overgrowth of organisms: Treatment with antibiotics such as linezolid may allow normal fungus or types of bacteria not killed by the antibiotic to overgrow and cause unwanted infections such as yeast infections. Contact your doctor if you experience fever or chills while taking this medication.

Phenylketonuria: The oral liquid form of linezolid contains aspartame, an ingredient that cannot be broken down in the body by people who have phenylketonuria (a condition where you are lacking the enzyme needed to break down phenylalanine). People with phenylketonuria should take linezolid tablets instead.

Seizures: This medication may cause seizures, especially for people with a history of seizures or who are at risk for seizures. Get immediate medical attention if you experience a seizure while taking this medication.

Serotonin syndrome: Severe reactions are possible when linezolid is combined with other medications that act on serotonin, such as tricyclic antidepressants and serotonin reuptake inhibitors, medications used to treat depression. These combinations must be avoided. Symptoms of a reaction may include muscle rigidity and spasms, difficulty moving, changes in mental state including delirium and agitation. Coma and death are possible.

If you are taking antidepressants, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Vision problems: Linezolid may cause vision problems, especially when used for longer than recommended. If you experience vision changes (e.g., blurred vision, changes in colour vision, trouble seeing clearly) while taking this medication, contact your doctor immediately.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children and adolescents less than 18 years old.

Seniors: People who are elderly may be more at risk of low sodium levels caused by linezolid.

For a full list of interactions, use the Drug Interaction Checker available on the Drugs.com website.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.