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 CLOMIPHENE CITRATE
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; competes with estrogen for binding at estrogen receptors in the hypothalamus, inhibiting negative feedback and increasing gonadotropin-releasing hormone (Gn RH) secretion, leading to increased LH and FSH release from the pituitary.
Moderate to severe pain relief; combinations are used to reduce abuse potential.
Treatment of ovulatory dysfunction in women desiring pregnancy,Off-label: male infertility (oligospermia), induction of ovulation in assisted reproductive technology
Oral: One tablet (naloxone 0.5 mg / pentazocine 50 mg) every 3-4 hours as needed for pain; maximum 12 tablets daily.
50 mg orally once daily for 5 days, starting on day 5 of menstrual cycle; may increase to 100 mg orally once daily for 5 days if ovulation not achieved.
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 5–7 days (120–168 hours) for the active zu-isomer, with a longer half-life for its metabolites. This prolonged half-life leads to accumulation with repeated dosing and sustained clinical effects.
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).
Hepatic metabolism; excreted in feces; active metabolites (possibly enterohepatic recirculation).
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.
Primarily fecal (approximately 50%), with about 8% renal excretion of unchanged drug and metabolites. Biliary excretion is significant, with enterohepatic recirculation contributing to prolonged elimination.
Pentazocine: Approximately 35-65% bound to plasma proteins (mainly albumin). Naloxone: Approximately 32-45% bound to plasma proteins (mainly albumin).
Approximately 80–90% bound to albumin, with significant binding to other plasma proteins including sex hormone-binding globulin (SHBG).
Pentazocine: Vd ~2-3 L/kg, indicating extensive tissue distribution. Naloxone: Vd ~2-3 L/kg, also indicating wide distribution.
Apparent volume of distribution is large, approximately 50–100 L/kg, indicating extensive tissue distribution and accumulation, particularly in the liver and reproductive organs.
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.
Oral: ~100% absorbed, but bioavailability is difficult to quantify due to extensive first-pass metabolism and enterohepatic cycling; essentially complete systemic exposure after oral administration.
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 specific dose adjustment guidelines; use with caution in severe renal impairment (Cr Cl <30 m L/min) due to limited 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 liver disease or hepatic dysfunction; no Child-Pugh based adjustments available.
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.
Not recommended for use in children; safety and efficacy not established.
Initiate with half the usual adult dose (one-half tablet) and titrate carefully due to increased sensitivity and risk of respiratory depression.
Not indicated for use in elderly patients; no specific dosing recommendations.
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.
Should not be used in patients with liver disease or abnormal uterine bleeding of undetermined origin.
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.
Ovarian enlargement/cysts; visual disturbances; multiple pregnancy; ovarian hyperstimulation syndrome; vasomotor symptoms; blurred vision; prolonged use may increase risk of borderline or invasive ovarian tumors.
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.
Pregnancy; liver disease or history; abnormal uterine bleeding of undetermined origin; ovarian cyst or enlargement due to polycystic ovary syndrome; hypersensitivity to clomiphene.
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.
No significant food interactions. Avoid excessive alcohol consumption as it may impair fertility.
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.
FDA Pregnancy Category X. Clomiphene citrate is contraindicated in pregnancy. First trimester exposure associated with neural tube defects, cleft palate, and syndactyly. Second and third trimester: no data due to contraindication. Risk of multiple gestation (5-12%) increases risks of preterm labor, low birth weight, and congenital anomalies.
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.
Excreted into breast milk; M/P ratio unknown. Clomiphene may reduce milk production due to anti-estrogenic effects. Because of potential for adverse reactions in nursing infants, women are advised not to breastfeed during treatment.
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 dose adjustments in pregnancy as drug is contraindicated. If pregnancy occurs, discontinue immediately. No pharmacokinetic studies in pregnant women; drug should not be used.
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 ovarian size and estradiol levels to reduce risk of ovarian hyperstimulation syndrome (OHSS). Use only in patients with ovulatory dysfunction; rule out pregnancy before each cycle. Limit to 6 treatment cycles due to increased risk of ovarian cancer with prolonged use.
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 clomiphene citrate exactly as prescribed, typically for 5 days starting on day 3-5 of menstrual cycle.,Ovulation usually occurs 5-10 days after the last dose; have intercourse every other day during this window.,Common side effects include hot flashes, mood swings, and visual disturbances; report persistent visual changes immediately.,Risk of multiple pregnancy (mainly twins) is increased; discuss with healthcare provider.,Avoid use if pregnant, have liver disease, or have abnormal vaginal bleeding.
"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 CLOMIPHENE CITRATE, 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.. CLOMIPHENE CITRATE is a Selective Estrogen Receptor Modulator (SERM) that works by Selective estrogen receptor modulator; competes with estrogen for binding at estrogen receptors in the hypothalamus, inhibiting negative feedback and increasing gonadotropin-releasing hormone (Gn RH) secretion, leading to increased LH and FSH release from the pituitary.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between NALOXONE HYDROCHLORIDE AND PENTAZOCINE HYDROCHLORIDE and CLOMIPHENE CITRATE 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 CLOMIPHENE CITRATE is: 50 mg orally once daily for 5 days, starting on day 5 of menstrual cycle; may increase to 100 mg orally once daily for 5 days if ovulation not achieved.. 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 CLOMIPHENE CITRATE 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. CLOMIPHENE CITRATE is classified as Category A/B. FDA Pregnancy Category X. Clomiphene citrate is contraindicated in pregnancy. First trimester exposure associated with neural tube defects, cleft palate, and syndactyly. Second and. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.