Flexid - Dosage | Interactions | Side effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Flexid contains levofloxacin - a synthetic antibacterial agent from a group of quinolone antibiotics. It exists in a dose of 250 mg and 500 mg.

It works on the enzyme DNA gyrase and topoisomerase IV, thus killing bacteria (bactericidal effect) which eliminates the cause of the infection.

The following infections can be successfully treated with this drug:

  • Acute bacterial sinusitis
  • Community-acquired pneumonia
  • Chronic bronchitis
  • Complicated skin infections
  • Complicated infection of the soft tissue
  • Complicated and uncomplicated urinary tract infections
  • Pyelonephritis
  • Chronic bacterial prostatitis

When you should not use Flexid?

  • If you are allergic to levofloxacin or other quinolones
  • Children and adolescents as they are still growing
  • If you suffer from epilepsy
  • If you have had adverse reactions during the application of quinolone antibiotics (e.g. muscle damage)

What should be considered when applying Flexid?

Flexid must be cautiously applied in the following conditions:

  • If you are over 65 years old
  • If you have had a cerebrovascular insult (stroke)
  • If you suffer from epilepsy
  • If you have mental problems
  • If you have heart problems
  • If you have diabetes
  • If you have problems with your kidneys or liver

It is likely that the methicillin-resistant Staphylococcus aureus (MRSA) is resistant to the effects of this drug, and there is no point in using this drug in patients who have infections caused by MRSA.

This drug may rarely cause tendon damage (usually damage to the Achilles tendon) which leads to tendon rupture. This side effect can occur after only a few days after you start taking Flexid but it also can occur several months after you stop taking this medicine. If you experience severe pain which intensifies with movement, contact your doctor immediately. If you experience symptoms of a tendon rupture, stop taking Flexid, and then immobilize and rest the affected tendons/muscles.

Considering that elderly patients have decreased renal function, it is necessary to adjust (decrease) the dose according to renal function.

Sometimes, Flexid can cause particularly difficult, bloody and persistent diarrhea which is associated with infection in the intestines caused by bacteria called Clostridium difficile. This infection can occur during the use of all antibiotics, including Flexid. If you notice diarrhea, especially if it is persistent and bloody, contact your doctor immediately.

Flexid can lower the threshold for the occurrence of epileptic seizures, which can induce epileptic seizure in people who already suffer from epilepsy. Therefore, it should not be administered in patients suffering from epilepsy.

Patients who have a deficiency of the enzyme known as glucose 6 phosphate dehydrogenase, should not take Flexid because it can lead to hemolytic anemia.

Very rarely Flexid can cause Stevens-Johnson syndrome, which is characterized by severe skin damage. If you notice any changes on the skin or mucosa, contact your doctor immediately.

In diabetics, it is recommended to monitor blood sugar levels more frequently while you are on Flexid therapy.

Flexid, as well as other quinolone antibiotics, may prolong the QT interval which causes dangerous heart arrhythmias. Patients who already have arrhythmias or take other medicines that can cause arrhythmia, should not take Flexid pills.

Cases of hepatic necrosis that can be life-threatening have been reported.

Considering that it can lead to a deterioration of muscle weakness, Flexid must not be administered in patients suffering from myasthenia gravis.

If you notice impaired vision or other eye problems, immediately discontinue administration of the drug and contact your doctor.

If you notice numbness or pain in the fingers on the arm or leg, immediately discontinue the use of the Flexid, because this is a sign of peripheral neuropathy. If you continue taking Flexid, peripheral neuropathy may become a permanent condition!

Flexid and pregnancy

FDA has classified this drug in group C (animal studies have shown possible adverse effects of the drug on fetus, but there are no studies in humans). The US CDC has recommended this medicine as the first line treatment to treat anthrax in pregnant women, because in this case, the benefit to the mother outweighs the risks for the child.

Flexid and lactation

Flexid passes into breast milk and may affect the infant. For this reason, it is recommended to stop breastfeeding while you are taking Flexid. Instead of breastfeeding your baby, you should use alternative commercial infant formula.

Although some authors believe that this drug is safe for use in lactating women, based on the information from available studies, it is better to stop breastfeeding during Flexid therapy.


Dosage depends primarily on the type of infection and its severity.

In the table below you can find the recommended dosage of the Flexid (according to PIL) in different types of infections

Indication - type of infection Recommended dosage regimen
Acute bacterial sinusitis 500 mg once daily during 10-14 days
Community-acquired pneumonia 500 mg once or twice daily during 7-14 days
Complicated urinary tract infections 500 mg once daily during 7-14 days
Uncomplicated urinary tract 250 mg once daily during 3 days
Pyelonephritis 500 mg once daily during 7-10 days
Prostatitis caused by bacteria 500 mg once daily during 4 weeks
Skin and soft tissue infections 500 mg once or twice daily during 7-14 days

Drink a tablet with a 1 cup of water. A few hours before and after administration of this drug, do not consume milk or milk products as well as calcium-fortified juices because they can reduce the utilization of this drug.

Other food does not affect this drug.


Drugs that can reduce utilization of Flexid:

  • OTC products containing iron, magnesium, zinc and calcium
  • Antacids (medicines for heartburn) containing aluminum, calcium or magnesium
  • Sucralfate

Flexid may affect the following drugs:

  • Cyclosporine
  • Vitamin K antagonists
  • Tricyclic antidepressants (amitriptyline, nortriptyline, imipramine, and others). Taking these medications together leads to an increased risk of QT prolongation and severe arrhythmias!
  • Erythromycin - Co-administration leads to an increased risk of arrhythmias
  • Amiodarone
  • Painkillers

Flexid side effects

Side effects of the Flexid include:

  1. Increased sensitivity to the sun (use sunscreens with a high SPF, wear a hat and avoid the solarium while you are taking this drug)
  2. Allergic reaction (occurs in 0.01% > of patients)
  3. Tendinitis and tendon rupture (occurs in 0.01-0.1% of patients)
  4. Paraesthesia or pain and numbness in the fingers on the arm or leg - signs of peripheral neuropathy (occurs in 0.01% > of patients). Immediately contact your doctor if you notice these symptoms.
  5. Digestive disorders
  6. Nervousness
  7. Insomnia
  8. Rapid heart beat
  9. Pain in the joints and muscles
  10. Vision impairment
  11. Prolongation of the QT interval
  12. Acute renal failure

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.

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