Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NALOXONE HYDROCHLORIDE AND PENTAZOCINE HYDROCHLORIDE vs EVISTA
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Pentazocine is a mixed agonist-antagonist opioid that binds to mu-opioid receptors (partial agonist) and kappa-opioid receptors (agonist), producing analgesia. Naloxone is a pure opioid antagonist that competitively blocks mu, kappa, and delta receptors; when administered orally, naloxone undergoes extensive first-pass metabolism, reducing systemic absorption and primarily blocking the effects of pentazocine if the combination is misused parenterally.
Selective estrogen receptor modulator (SERM) that binds to estrogen receptors, acting as an agonist in bone and antagonist in breast and uterine tissues.
Moderate to severe pain relief; combinations are used to reduce abuse potential.
Treatment and prevention of osteoporosis in postmenopausal women,Reduction in risk of invasive breast cancer in postmenopausal women with osteoporosis,Reduction in risk of invasive breast cancer in postmenopausal women at high risk for breast cancer
Oral: One tablet (naloxone 0.5 mg / pentazocine 50 mg) every 3-4 hours as needed for pain; maximum 12 tablets daily.
60 mg orally once daily.
Pentazocine has an elimination half-life of 2-3 hours in healthy adults, which may be prolonged in patients with hepatic impairment. Naloxone has a terminal half-life of 0.5-1.5 hours in adults, with a rapid decline in plasma levels; the short half-life limits its duration of opioid antagonism.
Terminal elimination half-life is approximately 32.5 hours (range 27-39 hours) for raloxifene and its glucuronide conjugates; clinically relevant for once-daily dosing.
Pentazocine is metabolized primarily by hepatic conjugation (glucuronidation) and oxidation via CYP2C19 and CYP2D6; naloxone is extensively metabolized by the liver, primarily via glucuronidation (UGT2B7).
Extensively metabolized in the liver via glucuronidation (UGT1A1, UGT1A8, UGT1A9) and CYP3A4-mediated oxidation.
Pentazocine is primarily metabolized in the liver and excreted in urine as conjugates of glucuronide and sulfate, with about 60% of a dose excreted renally within 24 hours as metabolites and unchanged drug (less than 5% unchanged). Naloxone undergoes extensive hepatic metabolism to naloxone-3-glucuronide, which is excreted renally; approximately 50% of a dose is excreted as conjugates in urine within 6 hours.
Raloxifene undergoes extensive glucuronidation; <0.1% excreted unchanged in urine. Approximately 95% is excreted in feces over 5 days (primarily as glucuronide conjugates). Renal elimination of unchanged drug is negligible (<0.1%).
Pentazocine: Approximately 35-65% bound to plasma proteins (mainly albumin). Naloxone: Approximately 32-45% bound to plasma proteins (mainly albumin).
>95% bound to plasma proteins, primarily albumin and α1-acid glycoprotein.
Pentazocine: Vd ~2-3 L/kg, indicating extensive tissue distribution. Naloxone: Vd ~2-3 L/kg, also indicating wide distribution.
Apparent Vd/F is approximately 1000-1500 L (not weight-based; extensive tissue distribution).
Oral pentazocine: 20-30% due to first-pass metabolism. Intramuscular pentazocine: 100%. Subcutaneous pentazocine: 100%. Oral naloxone: <2% due to extensive first-pass metabolism. Intramuscular and subcutaneous naloxone: 100%. Intravenous: 100% for both.
Absolute oral bioavailability is approximately 2% due to extensive first-pass glucuronidation; systemic exposure is dose-proportional.
GFR 30-50 m L/min: Administer every 6 hours; GFR 10-29 m L/min: Administer every 8-12 hours; GFR <10 m L/min: Administer every 12 hours or consider alternative.
No dose adjustment required for mild to moderate renal impairment (Cr Cl ≥30 m L/min). Not recommended in severe renal impairment (Cr Cl <30 m L/min) due to lack of data.
Child-Pugh Class A: No adjustment; Child-Pugh Class B: Reduce dose by 50% or extend interval; Child-Pugh Class C: Avoid use.
Contraindicated in patients with Child-Pugh Class B or C hepatic impairment. No specific dose adjustment recommended for Child-Pugh Class A, but use with caution.
Not recommended for children under 12 years. For older children (≥12 years): Pentazocine 50 mg (with naloxone 0.5 mg) orally every 3-4 hours as needed; maximum 6 tablets daily.
Safety and efficacy not established in pediatric patients; no recommended dose.
Initiate with half the usual adult dose (one-half tablet) and titrate carefully due to increased sensitivity and risk of respiratory depression.
No specific dose adjustment required; use standard adult dosing. Consider increased risk of venous thromboembolism and stroke in elderly women.
Risk of respiratory depression, particularly in elderly, cachectic, or debilitated patients; risk of addiction, abuse, and misuse; risk of neonatal opioid withdrawal syndrome with prolonged use during pregnancy; risk of life-threatening respiratory depression when used with benzodiazepines or other CNS depressants.
Increased risk of venous thromboembolism (VTE) and death from stroke. Not for use in women with active or history of VTE, including deep vein thrombosis, pulmonary embolism, and retinal vein thrombosis. Not for use in women with atrial fibrillation or other conditions that increase risk of stroke.
Respiratory depression; hypotension; increased intracranial pressure; seizure risk (pentazocine); opioid-induced hyperalgesia; adrenal insufficiency; severe hypotension; interaction with MAOIs; risk of dependence and withdrawal; gastrointestinal obstruction; impaired renal or hepatic function; head injury.
Risk of VTE; discontinue if VTE occurs. Risk of stroke; discontinue if stroke occurs or for prolonged immobilization. May increase risk of endometrial cancer; monitor for abnormal bleeding. Not for premenopausal women. Use with caution in patients with hepatic impairment or cholestasis. May increase triglycerides; monitor in patients with history of hypertriglyceridemia.
Hypersensitivity to pentazocine or naloxone; significant respiratory depression; acute or severe bronchial asthma; GI obstruction; known or suspected paralytic ileus; patients receiving MAOIs or within 14 days.
Active or history of VTE, pregnancy, women who may become pregnant, lactation, hypersensitivity to raloxifene, or any component of the formulation.
No specific food interactions are reported for this combination. However, grapefruit juice may theoretically affect metabolism via CYP3A4 (pentazocine is metabolized by CYP3A4), but clinical significance is unknown. Advise patients to maintain a consistent diet.
Avoid grapefruit and grapefruit juice as they may increase raloxifene levels. No other significant food interactions.
Pentazocine crosses the placenta; naloxone has limited placental transfer. No well-controlled human studies. First trimester: Risk cannot be excluded; avoid if possible. Second/Third trimester: Chronic use may cause fetal dependence; neonatal withdrawal syndrome reported. High doses near term may cause neonatal respiratory depression.
Pregnancy Category X. Raloxifene is contraindicated in pregnancy. In animal studies, raloxifene caused fetal abnormalities including skeletal malformations and cardiovascular defects. Human data are unavailable due to contraindication; use in pregnancy may cause fetal harm.
Pentazocine is excreted in breast milk in small amounts (estimated relative infant dose <3%). Naloxone is poorly bioavailable orally. Generally considered compatible with breastfeeding; monitor infant for sedation or poor feeding. M/P ratio for pentazocine is approximately 1.0.
Raloxifene is excreted in rat milk; no human data available. The M/P ratio is unknown. Due to potential adverse effects on the infant, breastfeeding is not recommended during therapy.
No established dose adjustments for pregnancy; however, pharmacokinetic changes (increased volume of distribution, enhanced clearance) may require higher or more frequent doses of pentazocine for adequate analgesia. Use lowest effective dose and shortest duration.
No dosing adjustments are applicable as raloxifene is contraindicated in pregnancy. Pharmacokinetic changes in pregnancy do not inform dose modifications due to the contraindication.
Naloxone in this fixed-dose combination is included to deter opioid abuse by reversing euphoria. The pentazocine component is a mixed agonist-antagonist opioid; naloxone has poor oral bioavailability but becomes active parenterally, precipitating withdrawal in opioid-dependent individuals. Use with caution in patients with impaired renal or hepatic function. Monitor for respiratory depression, especially in opioid-naive patients, as pentazocine alone can cause respiratory depression.
Monitor for venous thromboembolism; avoid in patients with active or history of VTE. May increase risk of stroke in postmenopausal women with coronary heart disease. No significant effect on breast cancer incidence. Administer with caution in hepatic impairment. Discontinue prior to prolonged immobilization or surgery.
Take exactly as prescribed; do not crush or inject tablets, as injected naloxone can cause severe withdrawal in opioid-dependent individuals.,This medication contains naloxone to discourage misuse; injection will cause withdrawal symptoms.,Report any signs of withdrawal (e.g., nausea, vomiting, sweating, agitation) or breathing difficulty.,Avoid alcohol and other central nervous system depressants as they increase risk of respiratory depression.,Do not use with other opioids unless directed, as effects are unpredictable.,Keep out of reach of children; accidental ingestion may cause severe respiratory depression.
Take once daily with or without food.,Report any signs of blood clots (leg pain/swelling, sudden chest pain, shortness of breath).,May cause hot flashes, leg cramps, or flu-like symptoms.,Avoid pregnancy; not indicated for premenopausal women.,Requires adequate calcium and vitamin D intake.
"Cobicistat is a potent CYP3A4 inhibitor used to boost the pharmacokinetics of antiretroviral agents like atazanavir and darunavir. Naloxone primarily undergoes glucuronidation via UGT1A6 and UGT2B7, with minor CYP3A4 metabolism. Concomitant use with Cobicistat may modestly increase naloxone exposure due to CYP3A4 inhibition, but this is unlikely to be clinically significant given naloxone's wide therapeutic index and short half-life."
"Fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), is primarily metabolized by cytochrome P450 (CYP) 1A2 and 2D6. Naloxone, an opioid antagonist, is reported to inhibit CYP1A2, potentially decreasing the clearance of fluvoxamine. This interaction may lead to increased fluvoxamine plasma concentrations, elevating the risk of serotonin syndrome, QT prolongation, and other dose-dependent adverse effects, especially in patients receiving high doses or those with hepatic impairment."
"Naloxone, an opioid receptor antagonist, may inhibit the cytochrome P450 isoenzyme CYP3A4, which is responsible for the metabolism of ivacaftor. Concomitant administration can lead to reduced clearance of ivacaftor, resulting in elevated serum concentrations. This increase may potentiate the therapeutic effects and adverse reactions of ivacaftor, such as hepatotoxicity and QT prolongation."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about NALOXONE HYDROCHLORIDE AND PENTAZOCINE HYDROCHLORIDE vs EVISTA, answered by our medical review team.
NALOXONE HYDROCHLORIDE AND PENTAZOCINE HYDROCHLORIDE is a Opioid Agonist-Antagonist that works by Pentazocine is a mixed agonist-antagonist opioid that binds to mu-opioid receptors (partial agonist) and kappa-opioid receptors (agonist), producing analgesia. Naloxone is a pure opioid antagonist that competitively blocks mu, kappa, and delta receptors; when administered orally, naloxone undergoes extensive first-pass metabolism, reducing systemic absorption and primarily blocking the effects of pentazocine if the combination is misused parenterally.. EVISTA is a Selective Estrogen Receptor Modulator that works by Selective estrogen receptor modulator (SERM) that binds to estrogen receptors, acting as an agonist in bone and antagonist in breast and uterine tissues.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between NALOXONE HYDROCHLORIDE AND PENTAZOCINE HYDROCHLORIDE and EVISTA 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 NALOXONE HYDROCHLORIDE AND PENTAZOCINE HYDROCHLORIDE is: Oral: One tablet (naloxone 0.5 mg / pentazocine 50 mg) every 3-4 hours as needed for pain; maximum 12 tablets daily.. The standard adult dose of EVISTA is: 60 mg orally once daily.. 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 NALOXONE HYDROCHLORIDE AND PENTAZOCINE HYDROCHLORIDE and EVISTA 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. NALOXONE HYDROCHLORIDE AND PENTAZOCINE HYDROCHLORIDE is classified as Category A/B. Pentazocine crosses the placenta; naloxone has limited placental transfer. No well-controlled human studies. First trimester: Risk cannot be excluded; avoid if possible. Second/Thi. EVISTA is classified as Category C. Pregnancy Category X. Raloxifene is contraindicated in pregnancy. In animal studies, raloxifene caused fetal abnormalities including skeletal malformations and cardiovascular defec. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.