Methazolamide 25mg Tablets
It is used to treat glaucoma.It may be given to you for other reasons. Talk with the doctor.
Drug Class
Antiglaucoma Agent
Pharmacologic Class
Carbonic Anhydrase Inhibitor
Pregnancy Category
C
FDA Approved
Jan 1958
DEA Schedule
Not Controlled
Overview
What is this medicine?
Methazolamide is a medication used to lower pressure inside the eye (intraocular pressure) in people with glaucoma. It works by reducing the amount of fluid produced in the eye. It can also act as a diuretic (water pill) by increasing the amount of salt and water your body gets rid of through urine.
How to Use This Medicine
Taking Your Medication
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 medication and follow the instructions closely. Continue taking your medication as prescribed by your doctor or healthcare provider, even if you're feeling well.
It's worth noting that this medication may increase the frequency of urination. To minimize sleep disturbances, try to avoid taking it too close to bedtime.
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. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you have questions about the best way to dispose of your medication, consult your pharmacist. You may also want to check if there are drug take-back programs available 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 medication and follow the instructions closely. Continue taking your medication as prescribed by your doctor or healthcare provider, even if you're feeling well.
It's worth noting that this medication may increase the frequency of urination. To minimize sleep disturbances, try to avoid taking it too close to bedtime.
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. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you have questions about the best way to dispose of your medication, consult your pharmacist. You may also want to check if there are drug take-back programs available 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
- Stay well-hydrated to prevent kidney stone formation.
- Report any unusual symptoms, especially muscle weakness, tingling, or severe fatigue, to your doctor immediately.
- Avoid driving or operating machinery until you know how this medication affects you, as it can cause drowsiness or dizziness.
- Limit alcohol consumption, as it may worsen dizziness or drowsiness.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
50 to 100 mg two or three times daily
Dose Range:
50 - 300 mg
Condition-Specific Dosing:
open-angle_glaucoma:
50 to 100 mg two or three times daily
secondary_glaucoma:
50 to 100 mg two or three times daily
preoperative_acute_congestive_glaucoma:
50 to 100 mg two or three times daily
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established
Adolescent:
Not established
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment recommended, monitor for adverse effects.
Moderate:
Use with caution; consider lower doses and monitor for adverse effects and electrolyte imbalances.
Severe:
Contraindicated in severe renal disease due to risk of acidosis and accumulation.
Dialysis:
Contraindicated; Methazolamide is not significantly dialyzable.
Hepatic Impairment:
Mild:
No specific adjustment recommended.
Moderate:
Use with caution; monitor for adverse effects and electrolyte imbalances.
Severe:
Contraindicated in severe hepatic insufficiency due to risk of hepatic encephalopathy.
Pharmacology
Mechanism of Action
Methazolamide is a potent carbonic anhydrase inhibitor. Carbonic anhydrase is an enzyme found in various tissues, including the ciliary body of the eye, renal tubules, and red blood cells. In the eye, inhibition of carbonic anhydrase decreases the secretion of aqueous humor, thereby lowering intraocular pressure (IOP). In the kidney, it inhibits carbonic anhydrase in the renal tubules, leading to increased excretion of bicarbonate, sodium, potassium, and water, resulting in diuresis and metabolic acidosis.
Pharmacokinetics
Absorption:
Bioavailability:
Not available (well absorbed orally)
Tmax:
6 to 8 hours
FoodEffect:
Food may delay absorption but does not significantly affect the extent of absorption.
Distribution:
Vd:
Not available
ProteinBinding:
Approximately 50-60%
CnssPenetration:
Yes (can cause CNS side effects)
Elimination:
HalfLife:
Approximately 14 hours
Clearance:
Not available
ExcretionRoute:
Renal (primarily unchanged)
Unchanged:
Approximately 25% to 30%
Pharmacodynamics
OnsetOfAction:
2 to 4 hours
PeakEffect:
6 to 8 hours
DurationOfAction:
10 to 18 hours
Safety & Warnings
Side Effects
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 immediately or seek emergency medical attention:
Signs of an allergic reaction: rash, hives, itching, red, swollen, blistered, or peeling skin (with or without fever), wheezing, tightness in the chest or throat, difficulty breathing, swallowing, or talking, unusual hoarseness, or swelling of the mouth, face, lips, tongue, or throat.
Signs of electrolyte problems: mood changes, confusion, muscle pain, cramps, or spasms, weakness, shakiness, balance changes, abnormal heartbeat, seizures, loss of appetite, or severe nausea and vomiting.
Signs of acidosis (too much acid in the blood): confusion, rapid breathing, rapid heartbeat, irregular heartbeat, severe stomach pain, nausea, vomiting, excessive sleepiness, shortness of breath, or feeling extremely tired or weak.
Changes in vision or hearing.
Ringing in the ears.
Abnormal burning, numbness, or tingling sensations.
Increased urination.
In rare cases, severe and potentially life-threatening effects have been associated with sulfa drugs, including liver problems, blood disorders, and severe skin reactions (Stevens-Johnson syndrome/toxic epidermal necrolysis). If you experience any of the following, seek medical help immediately:
Rash, red, swollen, blistered, or peeling skin.
Red or irritated eyes.
Sores in the mouth, throat, nose, or eyes.
Fever, chills, or sore throat.
New or worsening cough.
Extreme fatigue or weakness.
Bruising or bleeding.
Signs of liver problems: dark urine, fatigue, decreased appetite, nausea, stomach pain, light-colored stools, vomiting, or yellow skin and 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's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or persist, contact your doctor for guidance:
Diarrhea, nausea, or vomiting.
Changes in taste.
Decreased appetite.
Drowsiness.
Fatigue or weakness.
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns, consult 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, 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 immediately or seek emergency medical attention:
Signs of an allergic reaction: rash, hives, itching, red, swollen, blistered, or peeling skin (with or without fever), wheezing, tightness in the chest or throat, difficulty breathing, swallowing, or talking, unusual hoarseness, or swelling of the mouth, face, lips, tongue, or throat.
Signs of electrolyte problems: mood changes, confusion, muscle pain, cramps, or spasms, weakness, shakiness, balance changes, abnormal heartbeat, seizures, loss of appetite, or severe nausea and vomiting.
Signs of acidosis (too much acid in the blood): confusion, rapid breathing, rapid heartbeat, irregular heartbeat, severe stomach pain, nausea, vomiting, excessive sleepiness, shortness of breath, or feeling extremely tired or weak.
Changes in vision or hearing.
Ringing in the ears.
Abnormal burning, numbness, or tingling sensations.
Increased urination.
In rare cases, severe and potentially life-threatening effects have been associated with sulfa drugs, including liver problems, blood disorders, and severe skin reactions (Stevens-Johnson syndrome/toxic epidermal necrolysis). If you experience any of the following, seek medical help immediately:
Rash, red, swollen, blistered, or peeling skin.
Red or irritated eyes.
Sores in the mouth, throat, nose, or eyes.
Fever, chills, or sore throat.
New or worsening cough.
Extreme fatigue or weakness.
Bruising or bleeding.
Signs of liver problems: dark urine, fatigue, decreased appetite, nausea, stomach pain, light-colored stools, vomiting, or yellow skin and 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's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other symptoms that bother you or persist, contact your doctor for guidance:
Diarrhea, nausea, or vomiting.
Changes in taste.
Decreased appetite.
Drowsiness.
Fatigue or weakness.
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns, consult 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:
- Severe skin rash, blistering, or peeling (signs of Stevens-Johnson syndrome or toxic epidermal necrolysis)
- Unusual bleeding or bruising, persistent sore throat, fever, or extreme tiredness (signs of blood dyscrasias)
- Muscle weakness, cramps, or irregular heartbeat (signs of low potassium)
- Confusion, severe drowsiness, or unusual behavior changes
- Severe stomach pain, nausea, or vomiting
- Signs of kidney stones (e.g., severe back or side pain, blood in urine)
- Allergic reactions (e.g., swelling of face/lips/tongue, difficulty breathing, severe rash)
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.
Certain health conditions, including:
+ Acidic blood problems
+ Kidney disease
+ Liver disease
+ Low potassium levels (hypokalemia)
+ Low sodium levels (hyponatremia)
+ Poor adrenal function (adrenal insufficiency)
If you are currently taking acetazolamide, as this may interact with the medication.
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 will help determine if it is safe to take this medication with your existing health conditions and medications. Never start, stop, or change the dose of any medication without first consulting your doctor to ensure your safety.
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.
Certain health conditions, including:
+ Acidic blood problems
+ Kidney disease
+ Liver disease
+ Low potassium levels (hypokalemia)
+ Low sodium levels (hyponatremia)
+ Poor adrenal function (adrenal insufficiency)
If you are currently taking acetazolamide, as this may interact with the medication.
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 will help determine if it is safe to take this medication with your existing health conditions and medications. Never start, stop, or change the dose of any medication without first consulting your doctor to ensure your safety.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
Regular monitoring is crucial, so be sure to undergo eye pressure and vision checks as directed by your doctor. Additionally, have your blood work checked as scheduled, and discuss the results with your doctor.
Please note that this medication may interfere with certain laboratory tests. Therefore, it is vital to notify all your healthcare providers and laboratory personnel that you are taking this drug.
When taking this medication, you may be more susceptible to sunburn. Exercise caution when exposed to the sun, and inform your doctor if you experience increased sensitivity to sunlight.
If you are also taking aspirin, consult with your doctor, as high doses of aspirin combined with this medication can lead to severe adverse effects, including loss of appetite, rapid breathing, lethargy, coma, and even death.
If you are pregnant, planning to become pregnant, or breastfeeding, it is crucial to discuss the potential benefits and risks of this medication with your doctor to ensure the best possible outcome for you and your baby.
Regular monitoring is crucial, so be sure to undergo eye pressure and vision checks as directed by your doctor. Additionally, have your blood work checked as scheduled, and discuss the results with your doctor.
Please note that this medication may interfere with certain laboratory tests. Therefore, it is vital to notify all your healthcare providers and laboratory personnel that you are taking this drug.
When taking this medication, you may be more susceptible to sunburn. Exercise caution when exposed to the sun, and inform your doctor if you experience increased sensitivity to sunlight.
If you are also taking aspirin, consult with your doctor, as high doses of aspirin combined with this medication can lead to severe adverse effects, including loss of appetite, rapid breathing, lethargy, coma, and even death.
If you are pregnant, planning to become pregnant, or breastfeeding, it is crucial to discuss the potential benefits and risks of this medication with your doctor to ensure the best possible outcome for you and your baby.
Overdose Information
Overdose Symptoms:
- Severe electrolyte imbalance (e.g., profound hypokalemia, metabolic acidosis)
- Dehydration
- Drowsiness, confusion
- Nausea, vomiting
- Paresthesias
What to Do:
Call 1-800-222-1222 (Poison Control). Treatment is symptomatic and supportive, including correction of fluid and electrolyte imbalances. Gastric lavage may be considered if ingestion is recent. Methazolamide is not significantly dialyzable.
Drug Interactions
Contraindicated Interactions
- Salicylates (high-dose) - increased risk of metabolic acidosis and CNS toxicity
- Other carbonic anhydrase inhibitors (e.g., acetazolamide) - increased risk of systemic toxicity
Major Interactions
- Corticosteroids (e.g., prednisone) - increased risk of hypokalemia
- Digoxin - increased risk of digoxin toxicity due to hypokalemia
- Lithium - increased lithium excretion, leading to decreased lithium levels
- Methenamine compounds - decreased efficacy of methenamine due to alkalinization of urine
- Cyclosporine - increased cyclosporine levels
Moderate Interactions
- Other diuretics (e.g., loop, thiazide) - additive diuretic and potassium-wasting effects
- Amphetamines - increased amphetamine excretion due to urinary alkalinization
- Quinidine - increased quinidine excretion due to urinary alkalinization
- Oral hypoglycemics - potential for altered glucose control (rare)
Minor Interactions
- Sodium bicarbonate - may reduce efficacy of methazolamide
Monitoring
Baseline Monitoring
Serum Electrolytes (Na, K, Cl, HCO3)
Rationale: To establish baseline and identify pre-existing imbalances, especially hypokalemia and metabolic acidosis.
Timing: Prior to initiation of therapy.
Renal Function (BUN, Creatinine)
Rationale: To assess kidney function, as the drug is renally excreted and contraindicated in severe renal disease.
Timing: Prior to initiation of therapy.
Complete Blood Count (CBC)
Rationale: To check for baseline blood dyscrasias (rare but serious adverse effect).
Timing: Prior to initiation of therapy.
Intraocular Pressure (IOP)
Rationale: To establish baseline and assess the effectiveness of therapy for glaucoma.
Timing: Prior to initiation of therapy.
Routine Monitoring
Serum Electrolytes (Na, K, Cl, HCO3)
Frequency: Weekly for the first few weeks, then monthly or as clinically indicated.
Target: Within normal limits (e.g., K: 3.5-5.0 mEq/L, HCO3: 22-28 mEq/L)
Action Threshold: Significant deviations (e.g., K < 3.0 mEq/L, HCO3 < 20 mEq/L) require intervention (e.g., potassium supplementation, dose adjustment, discontinuation).
Renal Function (BUN, Creatinine)
Frequency: Every 3-6 months or as clinically indicated, especially in elderly or those with risk factors.
Target: Within normal limits
Action Threshold: Significant increase in BUN/Creatinine may indicate renal impairment and require dose adjustment or discontinuation.
Complete Blood Count (CBC)
Frequency: Periodically, especially if symptoms of blood dyscrasias (e.g., fever, sore throat, unusual bleeding/bruising) occur.
Target: Within normal limits
Action Threshold: Significant decrease in cell counts (e.g., severe anemia, leukopenia, thrombocytopenia) requires immediate discontinuation.
Intraocular Pressure (IOP)
Frequency: As determined by ophthalmologist, typically at follow-up visits.
Target: Target IOP as set by ophthalmologist (e.g., < 21 mmHg or lower depending on disease severity)
Action Threshold: Failure to achieve target IOP may require dose adjustment or alternative therapy.
Symptom Monitoring
- Signs of electrolyte imbalance (e.g., muscle weakness, cramps, fatigue, irregular heart beat, confusion, nausea, vomiting)
- Signs of metabolic acidosis (e.g., hyperventilation, fatigue, confusion)
- Signs of hypersensitivity reactions (e.g., rash, fever, sore throat, Stevens-Johnson syndrome)
- Signs of blood dyscrasias (e.g., unusual bleeding, bruising, persistent sore throat, fever, pallor)
- Gastrointestinal disturbances (e.g., nausea, vomiting, diarrhea, anorexia)
- Central nervous system effects (e.g., paresthesias, drowsiness, confusion, dizziness)
- Renal calculi symptoms (e.g., flank pain, hematuria)
Special Patient Groups
Pregnancy
Methazolamide is Pregnancy Category C. Animal studies have shown adverse effects on the fetus. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Trimester-Specific Risks:
First Trimester:
Potential for teratogenic effects observed in animal studies (e.g., limb defects, craniofacial anomalies).
Second Trimester:
Risk of electrolyte imbalance and metabolic acidosis in the mother, which could indirectly affect fetal well-being.
Third Trimester:
Risk of electrolyte imbalance and metabolic acidosis in the mother, potential for neonatal acidosis or electrolyte disturbances if used close to delivery.
Lactation
Methazolamide is excreted in human milk. Due to the potential for serious adverse reactions in the nursing infant (e.g., metabolic acidosis, growth inhibition), 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. Lactation risk is L3 (Moderate Concern).
Infant Risk:
Metabolic acidosis, electrolyte imbalance, potential for idiosyncratic reactions (e.g., sulfonamide-like effects).
Pediatric Use
Safety and effectiveness in pediatric patients have not been established. Use is generally not recommended due to lack of data and potential for serious adverse effects, including metabolic acidosis and growth retardation.
Geriatric Use
Elderly patients may be more susceptible to the effects of methazolamide, particularly electrolyte imbalances (hypokalemia, metabolic acidosis) and CNS side effects (drowsiness, confusion). Renal function should be closely monitored, and lower initial doses may be appropriate.
Clinical Information
Clinical Pearls
- Methazolamide is a sulfonamide derivative; caution in patients with sulfonamide allergy.
- Patients should be advised to maintain adequate fluid intake to prevent renal calculus formation.
- Paresthesias (tingling sensation) are a common and generally benign side effect, often occurring in the extremities.
- Monitor for signs of metabolic acidosis, especially in patients with pre-existing renal or respiratory compromise.
- Unlike acetazolamide, methazolamide has a longer half-life, allowing for less frequent dosing.
- Consider potassium supplementation if hypokalemia develops, especially in patients on concomitant diuretics or corticosteroids.
Alternative Therapies
- Topical Carbonic Anhydrase Inhibitors (e.g., dorzolamide, brinzolamide) - for glaucoma
- Beta-blockers (e.g., timolol, betaxolol) - for glaucoma
- Prostaglandin Analogs (e.g., latanoprost, travoprost) - for glaucoma
- Alpha-adrenergic Agonists (e.g., brimonidine) - for glaucoma
- Rho Kinase Inhibitors (e.g., netarsudil) - for glaucoma
- Osmotic Diuretics (e.g., mannitol, glycerol) - for acute angle-closure glaucoma
- Loop Diuretics (e.g., furosemide) - for fluid retention (different indication)
Cost & Coverage
Average Cost:
$15 - $50 per 30 tablets (25mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (Generic)
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 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 emergency medical attention. When seeking help, be prepared to provide details about the medication taken, including the amount and time of ingestion.