Methazolamide 50mg 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
Category C
FDA Approved
Jan 1958
DEA Schedule
Not Controlled
Overview
What is this medicine?
Methazolamide is a medication used to lower high pressure inside the eye, which is often caused by a condition called glaucoma. It works by reducing the amount of fluid your eye produces.
How to Use This Medicine
Taking Your Medication Correctly
To get the most benefit from your medication, take it exactly 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.
It's essential to note that this medication may increase the frequency of urination. To minimize sleep disturbances, try to avoid taking your medication too close to bedtime.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry location, avoiding the bathroom. Keep all medications in a secure place, out of the reach of children and pets. Dispose of any unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so by your pharmacist. If you have questions about the best way to dispose of your medication, consult with your pharmacist. You may also want to check if there are any 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, take it exactly 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.
It's essential to note that this medication may increase the frequency of urination. To minimize sleep disturbances, try to avoid taking your medication too close to bedtime.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry location, avoiding the bathroom. Keep all medications in a secure place, out of the reach of children and pets. Dispose of any unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so by your pharmacist. If you have questions about the best way to dispose of your medication, consult with your pharmacist. You may also want to check if there are any 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
- Maintain adequate hydration to prevent kidney stone formation.
- Report any unusual symptoms, especially tingling, numbness, muscle weakness, or severe fatigue.
- Avoid driving or operating machinery if you experience dizziness, drowsiness, or blurred vision.
- Wear medical alert identification if you have a history of severe allergic reactions to sulfonamides.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
50 mg to 100 mg two or three times daily
Dose Range:
50 - 100 mg
Condition-Specific Dosing:
glaucoma:
50 mg 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, but monitor for adverse effects.
Moderate:
Use with caution; monitor for metabolic acidosis and electrolyte imbalances. Dose reduction may be necessary.
Severe:
Use with caution; monitor closely for metabolic acidosis and electrolyte imbalances. Dose reduction likely necessary.
Dialysis:
Not well studied; caution advised. Methazolamide is not significantly dialyzable.
Hepatic Impairment:
Mild:
Use with caution.
Moderate:
Use with caution; monitor for signs of hepatic encephalopathy. Dose reduction may be necessary.
Severe:
Contraindicated in severe hepatic insufficiency due to risk of hepatic coma.
Pharmacology
Mechanism of Action
Methazolamide is a potent, reversible inhibitor of carbonic anhydrase. 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 in the ciliary body reduces the formation of bicarbonate ions, which in turn decreases the secretion of aqueous humor, leading to a reduction in intraocular pressure (IOP). In the kidney, it inhibits bicarbonate reabsorption, leading to increased excretion of bicarbonate, sodium, potassium, and water, resulting in a diuretic effect and metabolic acidosis.
Pharmacokinetics
Absorption:
Bioavailability:
Well absorbed (specific percentage not readily available)
Tmax:
6 to 8 hours
FoodEffect:
Not significantly affected by food
Distribution:
Vd:
Not readily available
ProteinBinding:
Approximately 50-60%
CnssPenetration:
Limited, but can cause CNS side effects
Elimination:
HalfLife:
Approximately 10 to 14 hours
Clearance:
Not readily available
ExcretionRoute:
Primarily renal
Unchanged:
Approximately 25-30%
Pharmacodynamics
OnsetOfAction:
2 to 4 hours
PeakEffect:
6 to 8 hours
DurationOfAction:
10 to 18 hours
Confidence:
Medium
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 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
+ Difficulty breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of electrolyte problems, including:
+ Mood changes
+ Confusion
+ Muscle pain, cramps, or spasms
+ Weakness
+ Shakiness
+ Balance changes
+ Abnormal heartbeat
+ Seizures
+ Loss of appetite
+ Severe upset stomach or vomiting
Signs of acidosis (too much acid in the blood), such as:
+ Confusion
+ Rapid breathing
+ Rapid heartbeat
+ Abnormal heartbeat
+ Severe stomach pain, upset stomach, or vomiting
+ Excessive sleepiness
+ Shortness of breath
+ Feeling extremely tired or weak
Changes in vision
Changes in hearing
Ringing in the ears
Abnormal burning, numbness, or tingling sensations
Increased urination
Rare but Serious Side Effects
In rare cases, sulfa drugs can cause severe and potentially life-threatening effects, including liver problems, blood disorders, and severe skin reactions (Stevens-Johnson syndrome/toxic epidermal necrolysis). If you experience any of the following symptoms, contact your doctor 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, such as:
+ 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's essential to discuss any concerns with your doctor. If you experience any of the following side effects, contact your doctor or seek medical attention if they bother you or persist:
Diarrhea
Upset stomach or vomiting
Changes in taste
Decreased appetite
Drowsiness
* Fatigue or weakness
Reporting Side Effects
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, 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
+ Difficulty breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of electrolyte problems, including:
+ Mood changes
+ Confusion
+ Muscle pain, cramps, or spasms
+ Weakness
+ Shakiness
+ Balance changes
+ Abnormal heartbeat
+ Seizures
+ Loss of appetite
+ Severe upset stomach or vomiting
Signs of acidosis (too much acid in the blood), such as:
+ Confusion
+ Rapid breathing
+ Rapid heartbeat
+ Abnormal heartbeat
+ Severe stomach pain, upset stomach, or vomiting
+ Excessive sleepiness
+ Shortness of breath
+ Feeling extremely tired or weak
Changes in vision
Changes in hearing
Ringing in the ears
Abnormal burning, numbness, or tingling sensations
Increased urination
Rare but Serious Side Effects
In rare cases, sulfa drugs can cause severe and potentially life-threatening effects, including liver problems, blood disorders, and severe skin reactions (Stevens-Johnson syndrome/toxic epidermal necrolysis). If you experience any of the following symptoms, contact your doctor 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, such as:
+ 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's essential to discuss any concerns with your doctor. If you experience any of the following side effects, contact your doctor or seek medical attention if they bother you or persist:
Diarrhea
Upset stomach or vomiting
Changes in taste
Decreased appetite
Drowsiness
* Fatigue or weakness
Reporting Side Effects
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:
- Severe skin reactions (e.g., rash, blistering, peeling skin, sores in the mouth or eyes)
- Signs of allergic reaction (e.g., hives, difficulty breathing, swelling of face/lips/tongue/throat)
- Signs of blood problems (e.g., unusual bleeding or bruising, persistent sore throat, fever, extreme tiredness, pale skin)
- Signs of liver problems (e.g., yellowing of skin or eyes, dark urine, severe stomach pain, nausea, vomiting)
- Signs of kidney stones (e.g., severe back or side pain, blood in urine)
- Signs of metabolic acidosis (e.g., confusion, rapid breathing, deep sighing, extreme tiredness, nausea, vomiting)
- Muscle weakness or cramps, irregular heartbeat (signs of low potassium)
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
This list is not exhaustive, and it is crucial to discuss all your medications and health conditions with your doctor. Please provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter (OTC) medications you are taking
Any natural products or supplements you are using
Vitamins you are taking
* Any existing health problems
Your doctor will help you determine whether it is safe to take this medication with your other medications and health conditions. Do not initiate, stop, or modify the dosage 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.
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
This list is not exhaustive, and it is crucial to discuss all your medications and health conditions with your doctor. Please provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter (OTC) medications you are taking
Any natural products or supplements you are using
Vitamins you are taking
* Any existing health problems
Your doctor will help you determine whether it is safe to take this medication with your other medications and health conditions. Do not initiate, stop, or modify the dosage 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. Regularly schedule check-ups with your doctor to monitor your eye pressure and eyesight as advised. Additionally, have your blood work checked as directed by your doctor and discuss the results with them.
Be aware that this medication may interfere with certain laboratory tests. Therefore, it is crucial 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 if you experience increased sensitivity to sunlight, inform your doctor promptly.
If you are also taking aspirin, consult with your doctor, as combining high doses of aspirin 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 vital to discuss the potential benefits and risks of this medication with your doctor to ensure the best possible outcome for you and your baby.
Be aware that this medication may interfere with certain laboratory tests. Therefore, it is crucial 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 if you experience increased sensitivity to sunlight, inform your doctor promptly.
If you are also taking aspirin, consult with your doctor, as combining high doses of aspirin 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 vital 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:
- Exaggerated side effects such as severe electrolyte imbalance (e.g., hypokalemia, hyperchloremic metabolic acidosis)
- CNS depression (e.g., drowsiness, confusion)
- Gastrointestinal disturbances (e.g., nausea, vomiting)
What to Do:
Seek immediate medical attention. Treatment is symptomatic and supportive. Induce emesis or perform gastric lavage. Maintain fluid and electrolyte balance. Monitor blood gases. Call 1-800-222-1222 for Poison Control.
Drug Interactions
Contraindicated Interactions
- High-dose salicylates (increased risk of CNS toxicity)
- Severe hepatic insufficiency
Major Interactions
- Other carbonic anhydrase inhibitors (e.g., acetazolamide, dorzolamide, brinzolamide) - increased risk of systemic toxicity
- Salicylates (especially high doses) - increased risk of metabolic acidosis and CNS toxicity
Moderate Interactions
- Corticosteroids (systemic) - increased risk of hypokalemia
- Diuretics (loop, thiazide) - increased risk of hypokalemia
- Cyclosporine - increased cyclosporine levels
- Lithium - decreased lithium excretion, leading to increased lithium levels and toxicity
- Methenamine - decreased efficacy of methenamine due to alkalinization of urine
- Sodium bicarbonate - may counteract the acidifying effect of methazolamide
Minor Interactions
- Not available
Monitoring
Baseline Monitoring
Intraocular Pressure (IOP)
Rationale: To establish baseline and assess treatment efficacy for glaucoma.
Timing: Prior to initiation of therapy
Serum Electrolytes (Potassium, Sodium, Chloride, Bicarbonate)
Rationale: To establish baseline and monitor for electrolyte imbalances (e.g., hypokalemia, metabolic acidosis).
Timing: Prior to initiation of therapy
Complete Blood Count (CBC) with differential
Rationale: To establish baseline and monitor for potential blood dyscrasias (e.g., aplastic anemia, agranulocytosis).
Timing: Prior to initiation of therapy
Renal Function (BUN, Serum Creatinine)
Rationale: To assess baseline renal function, as the drug is primarily renally excreted.
Timing: Prior to initiation of therapy
Liver Function Tests (ALT, AST, Bilirubin)
Rationale: To assess baseline hepatic function, especially given the contraindication in severe hepatic insufficiency.
Timing: Prior to initiation of therapy
Routine Monitoring
Intraocular Pressure (IOP)
Frequency: Regularly, as determined by ophthalmologist
Target: Individualized target IOP
Action Threshold: Failure to achieve target IOP, or significant fluctuations
Serum Electrolytes (Potassium, Bicarbonate)
Frequency: Periodically (e.g., every 1-3 months initially, then less frequently if stable)
Target: Potassium: 3.5-5.0 mEq/L; Bicarbonate: 22-29 mEq/L
Action Threshold: Potassium < 3.5 mEq/L, Bicarbonate < 20 mEq/L (metabolic acidosis)
Complete Blood Count (CBC) with differential
Frequency: Periodically (e.g., every 3-6 months or as clinically indicated)
Target: Within normal limits
Action Threshold: Significant decrease in WBC, RBC, or platelet counts
Renal Function (BUN, Serum Creatinine)
Frequency: Periodically (e.g., every 6-12 months or as clinically indicated)
Target: Within normal limits
Action Threshold: Significant increase in BUN or creatinine
Symptom Monitoring
- Signs of metabolic acidosis (e.g., fatigue, confusion, hyperventilation, nausea, vomiting)
- Signs of electrolyte imbalance (e.g., muscle weakness, cramps, irregular heartbeat, tingling/numbness)
- Signs of hypersensitivity reactions (e.g., rash, fever, sore throat, eye irritation, Stevens-Johnson syndrome, toxic epidermal necrolysis)
- Signs of blood dyscrasias (e.g., unusual bleeding or bruising, persistent sore throat, fever, pallor, fatigue)
- Signs of hepatic dysfunction (e.g., jaundice, dark urine, abdominal pain, unexplained nausea/vomiting)
- Changes in vision or eye discomfort
Special Patient Groups
Pregnancy
Methazolamide is classified as Pregnancy Category C. Animal studies have shown teratogenic effects (e.g., skeletal abnormalities) at doses higher than human therapeutic doses. There are no adequate and well-controlled studies in pregnant women. 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 teratogenicity based on animal data; avoid if possible.
Second Trimester:
Use with caution; monitor for fetal growth and development.
Third Trimester:
Use with caution; potential for electrolyte disturbances in the neonate.
Lactation
Methazolamide is excreted into breast milk. Due to the potential for serious adverse reactions in nursing infants (e.g., metabolic acidosis, growth retardation, sulfonamide-related reactions), 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.
Infant Risk:
L3 (Moderate risk) - Potential for metabolic acidosis, electrolyte imbalance, and sulfonamide-related adverse effects in the infant. Monitor infant for signs of adverse effects.
Pediatric Use
Safety and efficacy in pediatric patients have not been established. Use is generally not recommended due to lack of data and potential for serious adverse effects.
Geriatric Use
Geriatric patients may be more susceptible to the adverse effects of methazolamide, particularly electrolyte imbalances (e.g., hypokalemia, metabolic acidosis) and CNS effects (e.g., confusion, drowsiness). Renal function often declines with age, which can affect drug clearance. Start with lower doses and monitor closely.
Clinical Information
Clinical Pearls
- Methazolamide is a sulfonamide derivative; caution should be exercised in patients with known sulfonamide hypersensitivity.
- It is less potent than acetazolamide but has a longer duration of action, allowing for less frequent dosing.
- Patients should be advised to maintain adequate fluid intake to prevent the formation of renal calculi.
- Regular monitoring of serum electrolytes (especially potassium and bicarbonate) is crucial due to the risk of hypokalemia and metabolic acidosis.
- Patients should be educated on the symptoms of metabolic acidosis and electrolyte imbalance and advised to seek medical attention if they occur.
- Can cause paresthesias (tingling sensation in extremities), which is a common but usually benign side effect of carbonic anhydrase inhibitors.
Alternative Therapies
- Topical beta-blockers (e.g., timolol, betaxolol)
- Prostaglandin analogs (e.g., latanoprost, travoprost, bimatoprost)
- Alpha-adrenergic agonists (e.g., brimonidine, apraclonidine)
- Other carbonic anhydrase inhibitors (e.g., acetazolamide, dorzolamide, brinzolamide)
- Miotics (e.g., pilocarpine)
- Rho kinase inhibitors (e.g., netarsudil)
- Combination topical agents (e.g., dorzolamide/timolol)
- Surgical interventions (e.g., trabeculectomy, laser trabeculoplasty)
Cost & Coverage
Average Cost:
Varies, typically $20-$60 per 30 tablets (50mg)
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (preferred 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 medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.