Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ACETAZOLAMIDE vs ACTIQ
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Reversible inhibition of carbonic anhydrase, primarily in the proximal renal tubule, reducing hydrogen ion secretion and increasing bicarbonate, sodium, potassium, and water excretion. Also reduces aqueous humor formation via ocular carbonic anhydrase inhibition.
Opioid agonist; binds to mu-opioid receptors in the CNS, altering pain perception and response.
Edema due to congestive heart failure (adjunctive therapy),Drug-induced edema,Centrencephalic epilepsies (petit mal, unlocalized seizures),Chronic simple (open-angle) glaucoma,Secondary glaucoma,Preoperative lowering of intraocular pressure in acute angle-closure glaucoma,Altitude sickness (prevention and treatment),Off-label: Idiopathic intracranial hypertension, metabolic alkalosis, sleep apnea, bipolar disorder, cystinuria, hypokalemic periodic paralysis
Management of breakthrough pain in cancer patients aged 16 and older who are already receiving and tolerant to opioid therapy for their underlying persistent cancer pain
250-500 mg orally twice daily or 250 mg intravenously twice daily; for edema, 250-375 mg orally once daily; for altitude sickness, 250 mg orally every 8-12 hours.
200 mcg transmucosally, titrated upward as needed; initial dose for opioid-tolerant patients is 200 mcg, with additional doses possible after 15 minutes if needed. Maximum 4 doses per episode. At least 4 hours between episodes.
Terminal half-life approximately 10–15 hours; prolonged in renal impairment (up to 30+ hours).
Terminal half-life 0.83–2 hours (mean 1.3 h) in adults; note that context: transmucosal absorption leads to rapid onset but short duration; half-life is not correlated with clinical effect due to oral transmucosal route and rapid redistribution.
Primarily excreted unchanged in urine (70-100%). Minor metabolism via hydrolysis of acetyl group (possibly by plasma esterases) to acetazolamide, and glucuronide conjugation.
Primarily hepatic via CYP3A4 to inactive metabolites (norfentanyl, despropionylfentanyl, hydroxyfentanyl) and other metabolites; <7% excreted unchanged in urine.
Renal: ~90% unchanged drug via tubular secretion and glomerular filtration; minor biliary/fecal (<2%).
Primarily renal as metabolites (about 75% as metabolites, <10% unchanged). Fecal excretion accounts for <9%. Biliary excretion is minor.
~70–90% bound primarily to carbonic anhydrase in erythrocytes and plasma proteins (albumin).
Fentanyl is 80–85% bound to plasma proteins (primarily albumin and α1-acid glycoprotein).
0.2–0.3 L/kg; concentrates in tissues with high carbonic anhydrase content (RBCs, kidneys, eyes).
Approximately 4 L/kg (range 3–6 L/kg); large Vd indicates extensive tissue distribution and redistribution contributing to short duration.
Oral: ~100% (well absorbed); IV: 100%.
Oral transmucosal: 50% (range 47–54%) relative to IV; variable and enhanced by rapid absorption through buccal mucosa.
Cr Cl 10-50 m L/min: administer every 12 hours; Cr Cl <10 m L/min: avoid use (ineffective).
No specific GFR-based dose adjustment recommended; use with caution in severe renal impairment (Cr Cl < 30 m L/min) and consider dose reduction due to potential accumulation.
Child-Pugh class A: no adjustment; Child-Pugh class B-C: caution, reduce dose by 50% and monitor for encephalopathy.
Child-Pugh Class A/B: No adjustment. Child-Pugh Class C: Reduce initial dose to 100 mcg and titrate slowly; monitor closely for prolonged effects.
Children: 5-10 mg/kg/dose orally or IV every 8-12 hours; maximum 500 mg/dose.
Not approved for pediatric use; safety and efficacy not established in patients under 16 years.
Initiate at lowest effective dose (250 mg daily) due to increased risk of electrolyte disturbances and renal impairment.
Initiate at 100 mcg transmucosally; titrate slowly due to increased sensitivity and risk of respiratory depression. Monitor for adverse effects.
WARNING: Metabolically induced acidosis. Use with caution in patients with hepatic cirrhosis to avoid precipitation of hepatic encephalopathy. Not recommended for long-term use in patients with chronic noncongestive angle-closure glaucoma due to risk of increased intraocular pressure with lens displacement.
Risk of respiratory depression, addiction, abuse, and misuse; accidental ingestion can be fatal; concomitant use with benzodiazepines or CNS depressants may cause profound sedation, respiratory depression, coma, and death; not for use in opioid non-tolerant patients; risk of neonatal opioid withdrawal syndrome with prolonged use during pregnancy; serious, life-threatening, or fatal respiratory depression may occur even at recommended doses.
Sulfonamide hypersensitivity reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis) - discontinue at first sign of rash,Metabolic acidosis - monitor electrolytes, use with caution in patients with respiratory acidosis or those at risk,Hepatic impairment - contraindicated in cirrhosis; may precipitate hepatic encephalopathy,Renal impairment (Cr Cl <10 m L/min) - ineffective and may cause metabolic acidosis,Hematologic reactions (agranulocytosis, aplastic anemia) - monitor CBC,Hypercalciuria and renal stone formation - ensure adequate hydration,Drowsiness, confusion, fatigue - impaired ability to drive/operate machinery,Use in pregnancy - potential risk; cross-sensitivity with sulfonamides
Risk of respiratory depression; addiction, abuse, and misuse; interactions with CNS depressants; serotonin syndrome; adrenal insufficiency; severe hypotension; seizures; withdrawal; use in patients with head injuries, increased intracranial pressure, biliary tract disease, pancreatitis; risk of choking with lozenge; oral mucosal irritation; dental caries; hypokalemia; hyponatremia; use in elderly, cachectic, or debilitated patients.
Hypersensitivity to acetazolamide or any sulfonamide derivative,Severe hepatic cirrhosis or hepatic impairment,Severe renal impairment (Cr Cl <10 m L/min) or anuria,Hyponatremia or hypokalemia,Adrenocortical insufficiency (Addison's disease),Long-term use in chronic noncongestive angle-closure glaucoma,Metabolic acidosis
Significant respiratory depression; acute or severe bronchial asthma in an unmonitored setting or without resuscitative equipment; known or suspected paralytic ileus; hypersensitivity to fentanyl or any component; opioid non-tolerant patients; management of acute or postoperative pain including headache/migraine, dental pain, or emergency department use.
Avoid high doses of vitamin C or cranberry juice as they may acidify urine and decrease drug effectiveness. Maintain adequate hydration; no specific food restrictions.
No significant food interactions. Grapefruit juice may increase fentanyl levels, but specific studies with ACTIQ are lacking. Avoid alcohol, as it may increase sedation and respiratory depression risk.
First trimester: Avoid; associated with increased risk of congenital malformations (limb defects, hypospadias). Second and third trimesters: Use only if clearly needed; may cause fetal metabolic acidosis, electrolyte disturbances, and growth retardation.
FDA Pregnancy Category C. First trimester: limited human data; animal studies show increased resorptions and fetal growth restriction. Second/third trimester: chronic use may cause neonatal opioid withdrawal syndrome; avoid use during labor due to risk of neonatal respiratory depression.
Excreted into breast milk (M/P ratio approximately 0.25). Not recommended due to risk of sulfonamide-related adverse effects (e.g., kernicterus in jaundiced infants, hemolytic anemia in G6PD deficiency).
Excreted in breast milk; M/P ratio not established. Limited data suggest low levels, but risk of infant sedation and respiratory depression. Avoid use while breastfeeding unless potential benefit outweighs risk.
No standard dose adjustment recommended; pharmacokinetics altered (increased Vd, decreased Cmax) but clinical significance uncertain. Monitor for metabolic acidosis and adjust if necessary.
Due to increased plasma volume and hepatic metabolism in pregnancy, dose requirements may increase; adjust based on clinical response and tolerance. Avoid use during labor and delivery due to risk of neonatal respiratory depression; short-term use preferred.
Acetazolamide is a carbonic anhydrase inhibitor used for glaucoma, altitude sickness, and as a diuretic. Monitor serum electrolytes (especially potassium and bicarbonate) due to metabolic acidosis risk. Avoid in severe hepatic or renal impairment. Can cause paresthesias, especially in hands and feet. Use with caution in patients with sulfonamide allergy as cross-reactivity is possible but rare.
ACTIQ is a transmucosal immediate-release fentanyl formulation indicated for breakthrough cancer pain in opioid-tolerant patients. Initiate with the lowest strength (200 mcg) and titrate upward. Avoid use in opioid-naive patients due to risk of fatal respiratory depression. Place the unit between cheek and lower gum, not sublingually. Instruct patient not to bite or suck the unit. Monitor for sedation and respiratory depression. Multiple units may be used per episode if needed, but wait at least 4 hours before next episode. Dispose of partially used units by flushing down toilet.
Take exactly as prescribed; do not stop suddenly.,May cause tingling or numbness in fingers, toes, or mouth; this is usually temporary.,Drink plenty of fluids unless otherwise directed; avoid excessive alcohol.,Report unusual fatigue, muscle cramps, or rapid breathing to your doctor.,Avoid prolonged sun exposure; use sunscreen as photosensitivity may occur.,If used for altitude sickness, start 1-2 days before ascent and continue during climb.
Only use ACTIQ if you are already taking regular around-the-clock opioid pain medicine and are tolerant to opioids.,Do not use ACTIQ for short-term pain like after surgery, headache, or dental pain.,Place the unit in your cheek pouch, not under your tongue. Do not chew or suck it.,If you need more than 4 units per day, contact your doctor as your dose may need adjustment.,Store ACTIQ in a safe place away from children, as accidental ingestion can be fatal.,Dispose of unused or partially used units by flushing them down the toilet.
"Bosutinib, a potent CYP3A4 inhibitor, can significantly increase the serum concentration of acetazolamide, a carbonic anhydrase inhibitor, by reducing its hepatic metabolism. This elevation may potentiate acetazolamide's adverse effects, including metabolic acidosis, electrolyte imbalances (e.g., hypokalemia), and paresthesias, especially in patients with renal impairment. Clinicians should monitor for signs of acetazolamide toxicity when coadministered with bosutinib."
"Acetazolamide, a carbonic anhydrase inhibitor, can cause metabolic acidosis and decrease renal tubular secretion of metformin, potentially increasing metformin plasma concentrations. This combination may elevate the risk of lactic acidosis, a rare but serious adverse effect of metformin. Additionally, acetazolamide-induced hypokalemia can exacerbate metformin-associated hyperlactatemia."
"Acetazolamide, a carbonic anhydrase inhibitor, increases urinary pH and promotes bicarbonate excretion, leading to metabolic alkalosis. This systemic alkalinization enhances renal tubular reabsorption of lithium, paradoxically decreasing lithium clearance and increasing serum lithium concentrations. Clinically, this can precipitate lithium toxicity, manifesting as nausea, tremor, ataxia, or confusion, particularly in patients on stable lithium regimens."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ACETAZOLAMIDE vs ACTIQ, answered by our medical review team.
ACETAZOLAMIDE is a Carbonic Anhydrase Inhibitor that works by Reversible inhibition of carbonic anhydrase, primarily in the proximal renal tubule, reducing hydrogen ion secretion and increasing bicarbonate, sodium, potassium, and water excretion. Also reduces aqueous humor formation via ocular carbonic anhydrase inhibition.. ACTIQ is a Opioid Analgesic that works by Opioid agonist; binds to mu-opioid receptors in the CNS, altering pain perception and response.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ACETAZOLAMIDE and ACTIQ depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of ACETAZOLAMIDE is: 250-500 mg orally twice daily or 250 mg intravenously twice daily; for edema, 250-375 mg orally once daily; for altitude sickness, 250 mg orally every 8-12 hours.. The standard adult dose of ACTIQ is: 200 mcg transmucosally, titrated upward as needed; initial dose for opioid-tolerant patients is 200 mcg, with additional doses possible after 15 minutes if needed. Maximum 4 doses per episode. At least 4 hours between episodes.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between ACETAZOLAMIDE and ACTIQ in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. ACETAZOLAMIDE is classified as Category C. First trimester: Avoid; associated with increased risk of congenital malformations (limb defects, hypospadias). Second and third trimesters: Use only if clearly needed; may cause f. ACTIQ is classified as Category C. FDA Pregnancy Category C. First trimester: limited human data; animal studies show increased resorptions and fetal growth restriction. Second/third trimester: chronic use may cause. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.