Flucytosine 500mg Capsules

Flucytosine is an antimetabolite that is converted to 5-fluorouracil (5-FU) within fungal cells by the enzyme cytosine deaminase. 5-FU is then metabolized to 5-fluorouridine triphosphate (5-FUTP) and 5-fluorodeoxyuridine monophosphate (5-FdUMP). 5-FUTP is incorporated into fungal RNA, disrupting protein synthesis. 5-FdUMP inhibits thymidylate synthetase, thereby interfering with fungal DNA synthesis. Mammalian cells lack cytosine deaminase, which accounts for the selective toxicity.

Urgent Side Effects: Seek Medical Help Right Away

Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:

Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of bleeding, including:
+ Vomiting or coughing up blood
+ Vomit that resembles coffee grounds
+ Blood in the urine
+ Black, red, or tarry stools
+ Bleeding from the gums
+ Abnormal vaginal bleeding
+ Unexplained bruises or bruises that increase in size
+ Uncontrollable bleeding
Signs of kidney problems, such as:
+ Inability to urinate
+ Changes in urine output
+ Blood in the urine
+ Sudden weight gain
Signs of low potassium levels, including:
+ Muscle pain or weakness
+ Muscle cramps
+ Abnormal heartbeat
Signs of low blood sugar, such as:
+ Dizziness
+ Headache
+ Feeling sleepy or weak
+ Shaking
+ Rapid heartbeat
+ Confusion
+ Hunger
+ Sweating
Chest pain or pressure
Shortness of breath
Sudden weight gain or swelling in the arms or legs
Confusion
Hallucinations (seeing or hearing things that are not there)
Seizures
Mood changes
Mouth irritation or mouth sores
Hearing loss
Changes in balance
Abnormal burning, numbness, or tingling sensations
Shakiness, difficulty moving, or stiffness
Severe and potentially life-threatening liver problems, characterized by:
+ Dark urine
+ Fatigue
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes

Other Possible Side Effects

Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it is essential to consult your doctor if you notice any of the following:

Drowsiness
Dry mouth
Stomach pain or diarrhea
Upset stomach or vomiting
Decreased appetite
Headache
* Fatigue or weakness

If you experience any of these side effects or any other unusual symptoms, contact your doctor for guidance. This is not an exhaustive list of possible side effects. If you have questions or concerns, consult your doctor.

Reporting Side Effects

You can report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch. Your doctor can also provide medical advice and guidance on managing side effects.

Before Taking This Medication: Important Information to Share with Your Doctor

It is essential to inform your doctor about the following:

Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
If you have a dihydropyrimidine dehydrogenase (DPD) deficiency, a condition that affects the body's ability to break down certain medications.

This list is not exhaustive, and it is crucial to discuss all your medications, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins, with your doctor and pharmacist. They will help you determine if it is safe to take this medication with your existing treatments and health conditions.

Remember, do not start, stop, or adjust the dosage of any medication without first consulting your doctor to ensure your safety.

It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. Regular blood tests will be necessary, as directed by your doctor, to monitor your condition. Be sure to discuss any concerns or questions with your doctor.

This medication may interfere with certain laboratory tests, so it is crucial to notify all your healthcare providers and laboratory personnel that you are taking this drug.

One of the potential risks associated with this medication is that it may impair the bone marrow's ability to produce essential blood cells, leading to severe and potentially life-threatening bleeding problems or infections. If you experience any signs of infection, such as fever, chills, severe sore throat, ear or sinus pain, cough, increased or discolored sputum, painful urination, mouth sores, or a wound that does not heal, or if you notice any bruising or bleeding, or feel extremely tired or weak, notify your doctor immediately.

You may be more prone to bleeding while taking this medication, so it is essential to exercise caution and avoid injuries. To minimize the risk of bleeding, use a soft toothbrush and an electric razor.

Additionally, you may be more susceptible to infections. To reduce this risk, wash your hands frequently and avoid close contact with people who have infections, colds, or flu.

This medication may also increase your sensitivity to the sun, making you more likely to sunburn. Take necessary precautions when exposed to the sun, and inform your doctor if you experience any unusual sunburn or sensitivity.

Do not take this medication for longer than prescribed, as this may increase the risk of a secondary infection.

If you are pregnant, planning to become pregnant, or breastfeeding, it is essential to discuss the potential benefits and risks of this medication with your doctor to ensure the best possible outcome for you and your baby.

• Amphotericin B (increased risk of flucytosine toxicity due to impaired renal function, though often used synergistically with careful monitoring)
• Cytarabine (antagonizes the antifungal activity of flucytosine)
• Zidovudine (increased risk of myelosuppression)

• Myelosuppressive agents (e.g., chemotherapy, radiation therapy - increased risk of bone marrow suppression)
• Nephrotoxic agents (e.g., aminoglycosides, cyclosporine, NSAIDs - may impair flucytosine excretion, increasing toxicity)
• Drugs that alter gut flora (e.g., broad-spectrum antibiotics - may reduce conversion of flucytosine to 5-FU by gut bacteria, potentially affecting efficacy or toxicity profile)

• Signs of myelosuppression (e.g., fever, sore throat, unusual bleeding/bruising, fatigue)
• Gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea, abdominal pain)
• Signs of liver dysfunction (e.g., jaundice, dark urine, persistent fatigue)
• Skin rash
• Headache, confusion, hallucinations (rare CNS effects)

Category C. Flucytosine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Animal studies have shown teratogenic effects.

L3 (Moderately Safe). Flucytosine is excreted into breast milk. Due to the potential for serious adverse reactions in the nursing infant (e.g., bone marrow suppression, gastrointestinal effects), a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

Safety and efficacy have been established in pediatric patients. Dosing is weight-based. Close monitoring of hematologic, renal, and hepatic function, as well as therapeutic drug monitoring, is crucial due to potential for toxicity and variability in drug clearance.

Use with caution in elderly patients, as they are more likely to have decreased renal function. Dose adjustments based on creatinine clearance are often necessary. Close monitoring of hematologic, renal, and hepatic function is essential.

• Flucytosine is almost always used in combination with amphotericin B for serious systemic fungal infections (e.g., cryptococcal meningitis, severe candidiasis) due to synergy and to prevent resistance.
• Therapeutic Drug Monitoring (TDM) is critical for flucytosine to optimize efficacy and minimize toxicity, especially myelosuppression.
• Administer capsules over 15 minutes to minimize gastrointestinal upset.
• Resistance can develop rapidly when flucytosine is used as monotherapy; therefore, combination therapy is standard.
• Patients should be well-hydrated to support renal excretion and minimize potential renal toxicity, especially when co-administered with nephrotoxic agents like amphotericin B.

• Amphotericin B (various formulations: conventional, lipid complex, liposomal)
• Azoles (e.g., Fluconazole, Voriconazole, Itraconazole, Posaconazole, Isavuconazole)
• Echinocandins (e.g., Caspofungin, Micafungin, Anidulafungin)

If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about your medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.