Fidaxomicin (oral)


Fidaxomicin belongs to a class of drugs known as macrolide antibiotics, and it is primarily used to fight a type of bacteria that is highly resistant to most other forms of medication. By preventing this bacteria's growth, fidaxomicin can alleviate the symptoms it causes: blood or mucus in a patient's stool, powerful cramping of the abdomen or stomach, persistent diarrhea and severe pain or discomfort in the stomach.

Fidaxomicin works only on this particular strain of bacteria, and will not provide relief for any other kind of infections in the body, including all of those that are viral in nature. Although it is not absorbed by the body, this medication does navigate to the intestines, and there it takes on the task of fighting the harmful bacteria causing the problem.

It should be taken orally, either once or twice daily, at your doctor's direction, and may be ingested with or without a meal. Ideally, it should be taken at the same time each day so your body becomes acclimated to it and so that you remember each day to take it. It is very important to use up the entire amount that has been prescribed for you, even if you begin to feel better long before the prescription has been used up.

Condition treated

  • Severe diarrhea associated with clostridium difficile

Type Of Medicine

  • Macrolide antibiotics

Side Effects

It is possible for various side effects to be exhibited while you are being treated with fidaxomicin. Some of these are relatively mild in nature and will subside within a day or two all on their own, but others may be more serious and cause you discomfort, in which case you should report them to your doctor. In rare cases, fidaxomicin can cause a serious allergic reaction, and when that happens, you should seek medical attention at the earliest opportunity, before the symptoms worsen. In the most extreme cases, an allergic reaction can become life-threatening, so this situation should be taken seriously. Common signs of an allergic reaction include some or all of the following:

  • Hives and or rashes which appear on the skin
  • Extreme itchiness
  • Disorientation or dizziness
  • Difficulty breathing, often associated with tightness in the chest
  • Pronounced swelling that appears in the face, primarily in the neck, throat, tongue and lips

Some of the more serious side effects that might develop as a result of taking fidaxomicin include the following:

  • Black or tarry stools, possibly including blood as well
  • Signs of an infection, such as chills, persistent sore throat or fever
  • Vomiting up material that has the appearance of coffee grounds
  • Unusual and unexplained tiredness or weakness.


A standard dosage for patients who are being treated for clostridial infection, i.e. clostridium difficile-associated diarrhea, would normally be in the range of 200 mg, taken orally twice each day. This dosage should be continued for about 10 days and can be taken with or without a meal. It is extremely important that the entire 10 day period be observed and that the entire amount of fidaxomicin is used up as prescribed. Stopping short of the full prescription amount may allow the bacteria being targeted to develop greater resistance to the antibiotic properties of the medication.

While the 200 mg dosage may not be ideal for every patient, it is a good starting point from which your doctor may make adjustments upward or downward to achieve the optimal dosage. The optimal dosage for you personally will be an amount that achieves the desired result of killing the offensive bacteria with the least amount of medication.

If you should miss a dosage of fidaxomicin, it is permissible to take it as soon as you remember it, unless you are already nearing the time for the next regularly scheduled dosage. In that case, it is much better to simply skip the dosage you missed and wait until the next scheduled dosage. It's never a good idea to double up on doses simply to get back on schedule.


Interactions with other drugs may cause adverse effects in your body that are akin to side effects, and may be uncomfortable or painful. Interactions can also limit the effectiveness of fidaxomicin or other medications that you are taking. It is, therefore, inadvisable to be taking fidaxomicin with any other drug that has the potential to interact with it and cause some kind of diminution of its effectiveness.

To prevent this from happening, it is worth your while to prepare a list of medications that you are currently using, including all herbal supplements, vitamins, over the counter drugs and other prescription medications, as well as all the dosages of each of these. Your doctor can then review this list and make a determination on whether it will be necessary to discontinue usage of fidaxomicin or any of the other medications. It is also possible that a lowering of the dosage of some of your other medications will help to achieve the same avoidance of interactions.

It would be helpful to have a list of medications like this if you have a need to go to a healthcare clinic where your primary care doctor is not in residence, or if you have to visit an emergency room for some reason. Any doctor other than your own will not know what to prescribe in order to treat your condition, unless they have this list to refer to, so that drug interactions can be avoided. The specific drugs that are most commonly checked for by doctors to avoid interactions with fidaxomicin include all of the following:

  • Zantac
  • Zofran
  • Zyrtec
  • Tylenol
  • Vitamin B12
  • Xanax
  • Carvedilol
  • Omega-3 polyunsaturated fatty acids
  • Flonase
  • Ciprofloxacin
  • Ubiquinone
  • MiraLAX
  • Flonase
  • Keflex
  • Niaspan
  • Panthenol
  • Acetaminophen
  • Plavix
  • Promethazine
  • Omeprazole.

There is also one medical condition which is known to be seriously impacted by fidaxomicin, and that is QT prolongation, so if you have this medical condition, be sure to point it out to your doctor before agreeing to treatment with fidaxomicin.


As with most drugs, there are a few precautions or warnings that should be observed when taking fidaxomicin. If you know that you are allergic to fidaxomicin, you should alert your doctor to this fact immediately, so that it is not considered for treatment. If you have any other allergic reactions to pets, foods, preservatives or fabrics, make sure you let your doctor know about these as well, because it is possible for inert components of fidaxomicin to trigger some of those other allergies.

Before prescribing a program of treatment with fidaxomicin, your doctor will probably have a consultation with you in which your entire medical history is reviewed, so they can be aware of any potential problems from your past which could be triggered by using this drug. For instance, a previous infection related to Clostridium difficile would be important to let your doctor know about.

You should avoid receiving any kind of immunizations or vaccinations while using fidaxomicin, unless your doctor has urged you to do so, because there is a potential for fidaxomicin to reduce the effectiveness of any kind of live bacterial vaccine.

If you have some kind of surgery scheduled during the time frame that you will be treated with fidaxomicin, be sure to let your doctor know that you are being treated with this medication. It may be necessary to discontinue your usage of this drug or to lower its dosage at the time you are to go undergo surgery. Oral surgeries fall into the same category, so if you know you are going to have any kind of oral surgery, you should alert your dentist to the fact that you are being treated with fidaxomicin.

There is no data available from either human studies or animal studies that shows any kind of harm being passed on to infants by mothers who are being treated with fidaxomicin. Even though this is the case, it is not advised to be taking this drug if you are pregnant or thinking of becoming pregnant, because there is always the potential for trace amounts of any medication you take to be passed on to a fetus.

In that same vein, it is unknown whether or not fidaxomicin is passed on to a nursing infant through breast milk. This uncertainty makes it inadvisable to breast-feed at the same time as being treated with fidaxomicin. Women who become pregnant or wish to breast-feed should consult with the family doctor and have a thorough discussion about the potential risks of both of these.


This medication should be stored in a location that is well out of the reach of all pets and children, preferably high up where it cannot be accessed, even when standing on furniture. It should not be kept in a pill reminder container, since these are not equipped with locking mechanisms to prevent unwanted access.

The room where your fidaxomicin is stored should not be subject to high humidity, like there would be in a bathroom when showering or bathing occur. Extremes of temperature are to be avoided, especially the possibility of having your medication frozen. Room temperature is best for fidaxomicin, although temperatures in the range of 45 to 85 degrees Fahrenheit are acceptable.

Any expired or unused amount of fidaxomicin should be disposed of through proper methods, as recommended by your doctor or pharmacist. You can also consult the FDA website, which is maintained to provide guidelines for the safe disposal of medicines.


Fidaxomicin is a macrolide antibiotic medication used in the treatment of infections brought on by a clostridium difficile-associated bacteria, and it works by preventing the growth of this resistant bacteria. This medication does not carry many potential side effects with usage and does not interact with a great number of other drugs, so it is tolerated well by most patients for whom it is prescribed. It is important that all the medication being prescribed is used up by a patient, so as not to increase the resistance of the bacteria being targeted.