Acetazolamide

About Acetazolamide

Acetazolamide blocks carbonic anhydrase, an enzyme the eye uses to make its internal fluid and the kidneys use to handle bicarbonate, so it lowers eye pressure and acts as a mild diuretic. Tablets are labeled as an add-on for open-angle and secondary glaucoma and before surgery for acute angle-closure glaucoma, for certain epilepsies, for edema from heart failure or medicines, and to prevent or ease acute mountain sickness. The extended-release capsules are labeled only for glaucoma and mountain sickness, and the hospital injection for the tablet uses except mountain sickness.

For mountain sickness the label gives 500 to 1,000 mg a day in divided doses, preferably started 24 to 48 hours before the ascent and continued for 48 hours at altitude, or longer if needed. For glaucoma the extended-release dose is one 500 mg capsule morning and evening. For edema it is given once in the morning, often on alternate days.

Upset stomach, vomiting and loss of appetite can occur. MedlinePlus advises calling your doctor right away for numbness or tingling, more thirst or urination, drowsiness, confusion, fever, rash, blood in the urine, yellowing skin, a sore throat or unusual bleeding or bruising. As a sulfonamide it has rarely caused fatal reactions, including Stevens-Johnson syndrome, severe liver damage, anaphylaxis and blood disorders, so it is stopped at signs of a serious reaction, and blood counts and electrolytes are checked. It can cause kidney stones. It is not used with low sodium or potassium, marked kidney or liver disease, cirrhosis, adrenal failure or hyperchloremic acidosis, or long term in chronic noncongestive angle-closure glaucoma, and needs caution in emphysema. There is no boxed warning.

Taking Acetazolamide

How to take it

Tablets once a day or in divided doses, depending on the reason; extended-release capsules usually morning and evening, swallowed without crushing or chewing. For altitude sickness the label advises starting 24 to 48 hours before the ascent.

If you miss a dose

Take it as soon as you remember, unless it is almost time for the next dose; then skip the missed dose and continue your regular schedule. Do not take a double dose.

Storage

At room temperature in the original container, tightly closed, away from excess heat and moisture (not in the bathroom), and out of reach of children.

Interactions to know about

High-dose aspirin with it has caused coma and death. It raises phenytoin and cyclosporine levels, can lower primidone and lithium levels, strengthens amphetamines and quinidine, blocks methenamine, and can raise or lower blood sugar. Other carbonic anhydrase inhibitors are not advised with it, and sodium bicarbonate raises the risk of kidney stones. Alcohol adds to drowsiness, so do not drive until you know how it affects you.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Acetazolamide differs from pharmacy to pharmacy

Acetazolamide tablets are an old generic with many makers, so the price is mostly the dispensing fee and markup, and a flat-price generic list matters most for a short altitude course. The extended-release capsules have fewer makers and cost pharmacies more, so their quotes vary more.

Ways to pay less for Acetazolamide without insurance

• Ask whether acetazolamide tablets are on the pharmacy’s flat-price generic list.
• If extended-release capsules are prescribed, ask your prescriber whether tablets would suit you.
• For long-term treatment, ask for a ninety-day supply.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Acetazolamide

1. 1.When do I start it before my ascent, and for how long?
2. 2.Is it safe with my sulfa allergy?
3. 3.Does it interact with my aspirin, seizure medicine or lithium?
4. 4.Will I need blood tests while I take it?

Related medications