Cycloserine 250mg Capsules
It is used to treat TB (tuberculosis). It is used to treat a urinary tract infection (UTI).
Drug Class
Antitubercular agent
Pharmacologic Class
Cell wall synthesis inhibitor (D-alanine analog)
Pregnancy Category
Category C
FDA Approved
Jan 1955
DEA Schedule
Not Controlled
Overview
What is this medicine?
Cycloserine is an antibiotic used to treat serious forms of tuberculosis (TB), especially when other medicines haven't worked. It helps by stopping the TB bacteria from building their protective outer layer, which kills them. It's usually taken with other TB medicines.
How to Use This Medicine
Taking Your Medication Correctly
To get the most benefit from your medication, it's essential to use it as directed by your doctor. Carefully read all the information provided with your prescription, and follow the instructions closely. Continue taking your medication as prescribed by your doctor or healthcare provider, even if you start to feel better.
Storing and Disposing of Your Medication
To maintain the quality and safety of your medication, store it at room temperature in a dry place, avoiding bathrooms. Keep all medications in a secure location, out of the reach of children and pets. When disposing of unused or expired medications, do not flush them down the toilet or pour them down the drain unless specifically instructed to do so. Instead, consult with your pharmacist for guidance on the best disposal method. You may also want to explore local drug take-back programs in your area.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
To get the most benefit from your medication, it's essential to use it as directed by your doctor. Carefully read all the information provided with your prescription, and follow the instructions closely. Continue taking your medication as prescribed by your doctor or healthcare provider, even if you start to feel better.
Storing and Disposing of Your Medication
To maintain the quality and safety of your medication, store it at room temperature in a dry place, avoiding bathrooms. Keep all medications in a secure location, out of the reach of children and pets. When disposing of unused or expired medications, do not flush them down the toilet or pour them down the drain unless specifically instructed to do so. Instead, consult with your pharmacist for guidance on the best disposal method. You may also want to explore local drug take-back programs in your area.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Avoid alcohol completely while taking this medication, as it can increase serious side effects like seizures.
- Report any changes in mood, behavior, or thinking to your doctor immediately.
- Take this medication exactly as prescribed, even if you start to feel better. Do not skip doses.
- Take with food or milk if it causes stomach upset.
- You may be prescribed Vitamin B6 (pyridoxine) to help prevent some side effects; take it as directed.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
Initial: 250 mg orally every 12 hours for 2 weeks; then 250 mg orally every 8 hours or 250 mg orally every 6 hours, up to a maximum of 1000 mg/day.
Dose Range:
500 - 1000 mg
Condition-Specific Dosing:
Tuberculosis (MDR-TB):
250 mg orally every 12 hours, adjusted based on serum levels and tolerability, up to 1000 mg/day in divided doses.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
10-20 mg/kg/day orally divided every 12 hours, maximum 1000 mg/day.
Adolescent:
10-20 mg/kg/day orally divided every 12 hours, maximum 1000 mg/day.
Dose Adjustments
Renal Impairment:
Mild:
CrCl 50-80 mL/min: Monitor closely, consider lower end of dosing range.
Moderate:
CrCl 30-49 mL/min: 250 mg orally once daily.
Severe:
CrCl <30 mL/min: Contraindicated or significantly reduced dose (e.g., 250 mg every 24-48 hours) with close monitoring of serum levels.
Dialysis:
Hemodialysis: Administer dose after dialysis session. Peritoneal Dialysis: Not well studied, monitor levels closely.
Hepatic Impairment:
Mild:
No specific adjustment needed.
Moderate:
No specific adjustment needed.
Severe:
No specific adjustment needed, but monitor for CNS effects as hepatic encephalopathy can exacerbate neurotoxicity.
Pharmacology
Mechanism of Action
Cycloserine is a broad-spectrum antibiotic that inhibits bacterial cell wall synthesis. It acts as a structural analog of D-alanine, competitively inhibiting two enzymes involved in peptidoglycan synthesis: D-alanine racemase (which converts L-alanine to D-alanine) and D-alanine:D-alanine ligase (which catalyzes the formation of the D-alanine-D-alanine dipeptide). This prevents the incorporation of D-alanine into the peptidoglycan layer, leading to defective cell walls and bacterial cell death.
Pharmacokinetics
Absorption:
Bioavailability:
70-90%
Tmax:
4-8 hours
FoodEffect:
Minimal effect on absorption; may be taken with food to reduce gastrointestinal upset.
Distribution:
Vd:
0.6 L/kg
ProteinBinding:
<20%
CnssPenetration:
Yes
Elimination:
HalfLife:
10-12 hours (prolonged in renal impairment)
Clearance:
Not available
ExcretionRoute:
Renal (glomerular filtration)
Unchanged:
60-70% within 72 hours
Pharmacodynamics
OnsetOfAction:
Not immediate; requires accumulation to steady-state concentrations for therapeutic effect.
PeakEffect:
Achieved at steady-state concentrations, typically within 5-7 days of consistent dosing.
DurationOfAction:
Related to half-life; effects persist as long as therapeutic concentrations are maintained.
Safety & Warnings
Side Effects
Serious Side Effects: Seek Medical Attention Immediately
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor or seek medical help right away:
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
New or worsening behavioral or mood changes, including:
+ Depression
+ Thoughts of suicide
Confusion
Memory problems or loss
Dizziness or fainting
Seizures
Excessive sleepiness
Headache
Changes in speech
Shakiness
Muscle weakness
Shortness of breath
Sudden weight gain
Swelling in the arms or legs
Feeling extremely tired or weak
Abnormal burning, numbness, or tingling sensations
Other Possible Side Effects
Like all medications, this drug can cause side effects. However, many people do not experience any side effects or only have mild ones. If you have any side effects that bother you or do not go away, contact your doctor for advice.
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor or seek medical help right away:
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
New or worsening behavioral or mood changes, including:
+ Depression
+ Thoughts of suicide
Confusion
Memory problems or loss
Dizziness or fainting
Seizures
Excessive sleepiness
Headache
Changes in speech
Shakiness
Muscle weakness
Shortness of breath
Sudden weight gain
Swelling in the arms or legs
Feeling extremely tired or weak
Abnormal burning, numbness, or tingling sensations
Other Possible Side Effects
Like all medications, this drug can cause side effects. However, many people do not experience any side effects or only have mild ones. If you have any side effects that bother you or do not go away, contact your doctor for advice.
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Seizures or convulsions
- Severe dizziness or lightheadedness
- Confusion, disorientation, or memory problems
- Hallucinations (seeing or hearing things that aren't there)
- Severe depression or thoughts of harming yourself
- Unusual anxiety, agitation, or irritability
- Muscle weakness, numbness, or tingling in your hands or feet (peripheral neuropathy)
- Slurred speech
- Difficulty walking or loss of coordination
Before Using This Medicine
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 allergic reaction you experienced, including any symptoms that occurred.
If you have a history of certain health conditions, including:
+ Anxiety
+ Depression
+ Psychosis
+ Other mood disorders
+ Seizures
If you have kidney disease or any other kidney problems
If you consume alcohol or take medications that contain alcohol
This list is not exhaustive, and it is crucial to discuss all your medications, health problems, and concerns with your doctor and pharmacist. This includes:
All prescription and over-the-counter (OTC) medications
Natural products
* Vitamins
Your doctor and pharmacist need to be aware of all your medications and health problems to ensure it is safe for you to take this medication. Never start, stop, or change the dose of any medication without first consulting 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 allergic reaction you experienced, including any symptoms that occurred.
If you have a history of certain health conditions, including:
+ Anxiety
+ Depression
+ Psychosis
+ Other mood disorders
+ Seizures
If you have kidney disease or any other kidney problems
If you consume alcohol or take medications that contain alcohol
This list is not exhaustive, and it is crucial to discuss all your medications, health problems, and concerns with your doctor and pharmacist. This includes:
All prescription and over-the-counter (OTC) medications
Natural products
* Vitamins
Your doctor and pharmacist need to be aware of all your medications and health problems to ensure it is safe for you to take this medication. Never start, stop, or change the dose of any medication without first consulting your doctor.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. Until you understand how this drug affects you, avoid operating a vehicle and engaging in other activities that require alertness. Additionally, refrain from consuming alcohol while taking this medication. Do not exceed the prescribed duration of treatment, as this may increase the risk of a secondary infection. As directed by your doctor, undergo regular blood tests to monitor your condition. If you are pregnant, planning to become pregnant, or are breastfeeding, consult your doctor to discuss the potential benefits and risks of this medication to both you and your baby.
Overdose Information
Overdose Symptoms:
- Central nervous system (CNS) depression (drowsiness, lethargy)
- Psychosis
- Seizures
- Coma
- Headache
- Dizziness
- Confusion
- Tremor
- Hyperreflexia
What to Do:
Seek immediate medical attention or call Poison Control (1-800-222-1222). Treatment is supportive. Activated charcoal may be considered if ingestion is recent. Hemodialysis can effectively remove cycloserine from the body.
Drug Interactions
Contraindicated Interactions
- Alcohol (ethanol)
Major Interactions
- Isoniazid
- Ethionamide
- Phenytoin
Moderate Interactions
- Other CNS depressants (e.g., benzodiazepines, opioids, sedatives)
- Pyridoxine (Vitamin B6)
Monitoring
Baseline Monitoring
Renal function (BUN, serum creatinine)
Rationale: Cycloserine is primarily renally eliminated; impairment requires dose adjustment.
Timing: Prior to initiation of therapy
Liver function (ALT, AST, bilirubin)
Rationale: Although minimally metabolized, baseline assessment is prudent.
Timing: Prior to initiation of therapy
Mental status and neurological assessment
Rationale: To establish baseline for potential neurotoxic and psychiatric adverse effects.
Timing: Prior to initiation of therapy
Electrolytes
Rationale: To assess for any pre-existing imbalances that could exacerbate CNS effects.
Timing: Prior to initiation of therapy
Routine Monitoring
Serum cycloserine levels (Therapeutic Drug Monitoring)
Frequency: Weekly until stable, then monthly or as clinically indicated.
Target: 20-35 mcg/mL (peak, 2 hours post-dose)
Action Threshold: Levels >35 mcg/mL are associated with increased risk of CNS toxicity; levels <20 mcg/mL may indicate subtherapeutic dosing. Adjust dose accordingly.
Renal function (BUN, serum creatinine)
Frequency: Monthly or more frequently if clinically indicated.
Target: Within normal limits or stable for patient.
Action Threshold: Significant increase in BUN/creatinine may necessitate dose adjustment.
Neurological and psychiatric assessment
Frequency: Frequently, especially during dose titration and initiation.
Target: Absence of new or worsening symptoms.
Action Threshold: Development of new or worsening symptoms (e.g., anxiety, depression, psychosis, seizures, confusion, tremor, peripheral neuropathy) requires immediate evaluation and potential dose reduction or discontinuation.
Pyridoxine (Vitamin B6) supplementation
Frequency: Daily, if prescribed.
Target: Not applicable (supplementation to mitigate toxicity).
Action Threshold: Not applicable.
Symptom Monitoring
- Seizures
- Psychosis
- Depression
- Anxiety
- Confusion
- Dizziness
- Headache
- Tremor
- Peripheral neuropathy (numbness, tingling, weakness)
- Somnolence
- Insomnia
- Irritability
- Aggression
- Suicidal ideation
Special Patient Groups
Pregnancy
Cycloserine is classified as Pregnancy Category C. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Data are limited, but animal studies have shown adverse effects at high doses. Close monitoring of the mother and fetus is recommended.
Trimester-Specific Risks:
First Trimester:
Potential for teratogenicity, though human data are limited.
Second Trimester:
Risk of adverse effects on fetal development, but often used if essential for maternal health.
Third Trimester:
Risk of adverse effects on fetal development, but often used if essential for maternal health.
Lactation
Cycloserine is excreted into breast milk. The decision to breastfeed should consider the risk of infant exposure, the benefits of breastfeeding to the infant, and the benefits of treatment to the mother. Monitor the infant for potential adverse effects (e.g., feeding difficulties, drowsiness, irritability).
Infant Risk:
L3 (Moderately safe; monitor infant for adverse effects).
Pediatric Use
Cycloserine is used in pediatric patients for the treatment of tuberculosis, particularly drug-resistant forms. Dosing is weight-based (10-20 mg/kg/day). Close monitoring for neurotoxicity and serum levels is crucial in children.
Geriatric Use
Elderly patients may have reduced renal function, which can lead to higher cycloserine concentrations and increased risk of toxicity. Dose adjustments based on renal function are often necessary. Close monitoring for CNS adverse effects is particularly important in this population.
Clinical Information
Clinical Pearls
- Cycloserine is a second-line antitubercular drug, primarily used in multi-drug resistant tuberculosis (MDR-TB) regimens.
- Therapeutic drug monitoring (TDM) of serum cycloserine levels is highly recommended due to its narrow therapeutic index and significant dose-related neurotoxicity.
- Pyridoxine (Vitamin B6) supplementation (e.g., 50-100 mg/day) is often co-administered to reduce the risk of cycloserine-induced peripheral neuropathy and other neurotoxic effects.
- Psychiatric adverse effects (e.g., depression, anxiety, psychosis, suicidal ideation) are common and can be severe; patients require careful monitoring and prompt intervention if these symptoms develop.
- Alcohol consumption is strictly contraindicated due to a significant increase in the risk of seizures and other neurotoxic effects.
- Ensure adequate renal function before and during therapy, as dose adjustments are critical in renal impairment.
Alternative Therapies
- Bedaquiline
- Delamanid
- Linezolid
- Clofazimine
- Ethionamide
- Para-aminosalicylic acid (PAS)
- Injectable agents (e.g., Amikacin, Kanamycin, Capreomycin - though many are being phased out for oral regimens)
Cost & Coverage
Average Cost:
Varies widely, typically $1000-$3000+ per 30 capsules (250mg)
Generic Available:
Yes
Insurance Coverage:
Tier 3 or 4 (Non-preferred brand/specialty drug), may require prior authorization.
General Drug Facts
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 this medication, don't hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When reporting the incident, be prepared to provide details about the medication taken, the amount, and the time it occurred.