Methazolamide (Neptazane) is a carbonic anhydrase inhibitor (like acetazolamide) that increases urinary volume and alters the blood and urinary PH. It is used in the treatment of patients with chronic open-angle glaucoma.

Methazolamide Uses:

• Glaucoma:

  • It is indicated for the treatment of chronic open-angle or secondary glaucoma.
  • It is also used for the short-term treatment of acute angle-closure glaucoma before surgery.

Methazolamide (Neptazane) Dose in Adults:

Methazolamide (Neptazane) Dose in the treatment of Glaucoma:

• Oral: 50 to 100 mg twice or thrice daily.

Use in Children:

Not indicated.

Pregnancy Risk Factor C

• Animal reproduction studies showed adverse pregnancy outcomes.

Use of methazolamide while breastfeeding

• It is unknown if the drug will be excreted into breastmilk.
• The risk of serious adverse events in infants can be very real.
• Therefore, it is important to weigh the advantages of breastfeeding and the risks to the infant from drug exposure. It is not advised to breastfeed.

Dose in Kidney Disease:

It is contraindicated in advanced renal dysfunction.

Dose in Liver disease:

It is contraindicated in advanced liver disease.

Side effects of Methazolamide (Neptazane):

• Central Nervous System:

  • Confusion
  • Drowsiness
  • Fatigue
  • Flaccid Paralysis
  • Malaise
  • Paresthesia
  • Seizure

• Dermatologic:

  • Erythema Multiforme
  • Skin Photosensitivity
  • Skin Rash
  • Stevens-Johnson Syndrome
  • Toxic Epidermal Necrolysis
  • Urticaria

• Endocrine & Metabolic:

  • Electrolyte Disturbance
  • Glycosuria
  • Metabolic Acidosis

• Gastrointestinal:

  • Decreased Appetite
  • Diarrhea
  • Dysgeusia
  • Melena
  • Nausea
  • Vomiting

• Genitourinary:

  • Crystalluria
  • Hematuria

• Hematologic & Oncologic:

  • Agranulocytosis
  • Aplastic Anemia
  • Bone Marrow Depression
  • Hemolytic Anemia
  • Immune Thrombocytopenia
  • Leukopenia
  • Pancytopenia

• Hepatic:

  • Fulminant Hepatic Necrosis
  • Hepatic Insufficiency

• Hypersensitivity:

  • Anaphylaxis
  • Hypersensitivity Reaction

• Ophthalmic:

  • Myopia

• Otic:

  • Auditory Disturbance
  • Tinnitus

• Renal:

  • Nephrolithiasis
  • Polyuria

• Miscellaneous:

  • Fever

Contraindications to Methazolamide (Neptazane):

• Advanced liver or kidney dysfunction
• Failure of the adrenal glands
• Cirrhosis
• Hyperchloremic acidosis;
• Hyponatremia;
• Hypokalemia
• Angle-closure Glaucoma: Long-term Treatment

Warnings and precautions

• CNS effects

  • It can cause CNS depression, and may impair mental or physical abilities. 
  • It should be used with caution by patients who are required to maintain mental alertness for tasks such as driving or operating heavy machinery.

• Electrolyte disturbance:

  • Hypokalemia can occur during treatment. Patients should be closely monitored for clinical signs and potassium levels should also be checked.

• Allergy to sulfonamide ("sulfa")

  • Patients with a history sulfa-drug allergy are generally advised to avoid drugs containing the sulfonamide groups. Cross-sensitivity is possible.
  • However, the latest recommendations don't recommend completely avoiding drugs that have a sulfonamide-related group. 
  • It is important to exercise caution. Cross-sensitivity reactions are very unlikely.
  • This is particularly true for non-antibiotics sulfonamide-containing drugs.
  • However, T-cell-mediated (type I) reactions (eg maculopapular skin rash) can also occur.
  • The mechanisms behind these reactions are not fully understood.
  • Avoid drugs that have caused severe reactions in patients who have used the same drug class previously.

• Diabetes:

  • Patients suffering from diabetes mellitus or prediabetes should avoid this as their glucose control could be impaired.

• Hepatic impairment

  • Patients suffering from liver disease should not take the drug, as it can cause hepaticencephalopathy.
  • Patients with liver impairments or cirrhosis are not advised to take the drug.

• Respiratory disease

  • It can worsen respiratory acidosis. Patients with chronic lung diseases like chronic obstructive or chronic pulmonary disease should not use it.

Methazolamide: Drug Interaction

Monitoring parameters:

• CBC and platelet count at baseline and periodically therafter.
• serum electrolytes periodically (watch for hypokalemia.
• Arterial blood gases if required (for metabolic acidosis.

How to administer methazolamide (Neptazane)?

It is administered orally without regard to meals.

Mechanism of action of Methazolamide (Neptazane):

• It acts as a noncompetitive inhibitor for the enzyme carbonic anhydrase. 
• It is located near the luminal edge of cells in the proximal tubeule.
• Inhibiting the carbonic anhydrase enzyme causes an increase of the volume of urine, and changes its pH (the urine becomes alkaline).
• This results in a decrease in excretion of titratable acids and ammonia.

Onset of action:

• Slow in comparison with acetazolamide (2-4 hours)

Peak effect:

• 6-8 hours

Duration:

• 10-18 hours

Absorption:

• Slow

Protein binding:

• About 55%

Metabolism:

• Slowly from the gastrointestinal tract

Half-life elimination:

• About 14 hours

Excretion:

• Urine (about 25% as unchanged drug)

International Brands of Methazolamide:

• Neptazane
• Glaumetax
• Mezomine

Methazolamide Brands Names in Pakistan:

No Brands Available in Pakistan.