Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ACTIQ vs ATMEKSI
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Opioid agonist; binds to mu-opioid receptors in the CNS, altering pain perception and response.
ATMEKSI (atazanavir/cobicistat) is a fixed-dose combination of atazanavir, an HIV-1 protease inhibitor that inhibits viral protease, preventing cleavage of viral polyproteins and resulting in immature non-infectious virions, and cobicistat, a pharmacokinetic enhancer that inhibits CYP3A, increasing atazanavir exposure.
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
Treatment of HIV-1 infection in adults and pediatric patients weighing at least 35 kg,Off-label use as part of antiretroviral therapy in treatment-experienced patients with viral suppression
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.
1.5 mg/kg IV every 4 weeks
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.
Terminal elimination half-life is 12 hours; renally impaired patients have prolonged half-life up to 24 hours.
Primarily hepatic via CYP3A4 to inactive metabolites (norfentanyl, despropionylfentanyl, hydroxyfentanyl) and other metabolites; <7% excreted unchanged in urine.
Atazanavir is metabolized by CYP3A4; cobicistat is metabolized by CYP3A and to a minor extent by CYP2D6.
Primarily renal as metabolites (about 75% as metabolites, <10% unchanged). Fecal excretion accounts for <9%. Biliary excretion is minor.
Primarily renal (80% unchanged) and biliary/fecal (15% as metabolites).
Fentanyl is 80–85% bound to plasma proteins (primarily albumin and α1-acid glycoprotein).
95% bound to albumin and alpha-1-acid glycoprotein.
Approximately 4 L/kg (range 3–6 L/kg); large Vd indicates extensive tissue distribution and redistribution contributing to short duration.
2.0 L/kg, indicating extensive tissue distribution.
Oral transmucosal: 50% (range 47–54%) relative to IV; variable and enhanced by rapid absorption through buccal mucosa.
Oral: 60-70% due to first-pass metabolism.
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.
GFR 15-29 m L/min: 1.0 mg/kg IV every 4 weeks; GFR <15 m L/min: not recommended
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.
Child-Pugh A: no adjustment; Child-Pugh B: 1.0 mg/kg IV every 4 weeks; Child-Pugh C: not recommended
Not approved for pediatric use; safety and efficacy not established in patients under 16 years.
Age 2-17 years: 1.5 mg/kg IV every 4 weeks; maximum 120 mg per dose
Initiate at 100 mcg transmucosally; titrate slowly due to increased sensitivity and risk of respiratory depression. Monitor for adverse effects.
No specific adjustment; monitor renal function and reduce dose if GFR <30 m L/min
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.
None
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.
Hepatotoxicity, especially in patients with pre-existing liver disease or elevated transaminases,Nephrolithiasis and cholelithiasis,Cardiac conduction abnormalities (PR interval prolongation),Risk of developing resistance if not used with other antiretrovirals,Renal impairment (cobicistat decreases estimated creatinine clearance)
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.
Concomitant use with drugs highly dependent on CYP3A for clearance (e.g., alfuzosin, rifampin, ergot derivatives, St. John's wort, lovastatin, simvastatin, sildenafil for pulmonary arterial hypertension),Severe hepatic impairment (Child-Pugh Class B or C)
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.
Avoid alcohol (may exacerbate CNS effects). Grapefruit juice may increase atomoxetine exposure; limit consumption. High-fat meals do not significantly affect absorption.
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.
First trimester: Limited human data; animal studies show no teratogenicity at therapeutic doses. Second and third trimesters: No known fetal risks. Avoid use during organogenesis unless benefit outweighs risk.
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.
Not recommended during breastfeeding. M/P ratio unknown. Excreted in animal milk; potential for serious adverse reactions in nursing infants.
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.
No dose adjustment required in pregnancy. Pharmacokinetic profile unchanged.
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.
ATMEKSI (atomoxetine) is a selective norepinephrine reuptake inhibitor (NRI) indicated for ADHD. It has a slower onset of action (2-4 weeks) compared to stimulants. Monitor for hepatotoxicity and suicidal ideation, especially in children and adolescents. Use cautiously with hepatic impairment (reduce dose) and CYP2D6 poor metabolizers (need lower dose). Avoid concurrent MAOIs. May cause orthostatic hypotension and urinary retention.
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.
Take ATMEKSI exactly as prescribed; do not change dose without consulting your doctor.,It may take 2-4 weeks to notice improvement in symptoms.,Avoid alcohol and grapefruit juice as they may affect drug levels.,Report any signs of liver problems (yellowing of skin/eyes, dark urine, abdominal pain) or suicidal thoughts immediately.,May cause dizziness or fainting, especially when standing up; rise slowly.,Do not stop abruptly without medical advice.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ACTIQ vs ATMEKSI, answered by our medical review team.
ACTIQ is a Opioid Analgesic that works by Opioid agonist; binds to mu-opioid receptors in the CNS, altering pain perception and response.. ATMEKSI is a PDE5 Inhibitor that works by ATMEKSI (atazanavir/cobicistat) is a fixed-dose combination of atazanavir, an HIV-1 protease inhibitor that inhibits viral protease, preventing cleavage of viral polyproteins and resulting in immature non-infectious virions, and cobicistat, a pharmacokinetic enhancer that inhibits CYP3A, increasing atazanavir exposure.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ACTIQ and ATMEKSI 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 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.. The standard adult dose of ATMEKSI is: 1.5 mg/kg IV every 4 weeks. 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 ACTIQ and ATMEKSI 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. 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. ATMEKSI is classified as Category C. First trimester: Limited human data; animal studies show no teratogenicity at therapeutic doses. Second and third trimesters: No known fetal risks. Avoid use during organogenesis u. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.