MEPERIDINE HYDROCHLORIDE PRESERVATIVE FREE
Clinical safety rating: avoid
Positive evidence of fetus risks but benefits may outweigh risks in some cases
Meperidine is a synthetic opioid agonist that exerts its analgesic effects by binding to mu-opioid receptors in the central nervous system, thereby mimicking the actions of endogenous opioids. It also has some kappa-opioid receptor activity and weak serotonergic effects.
| Metabolism | Meperidine is primarily metabolized in the liver via hydrolysis to meperidinic acid and via N-demethylation to normeperidine (an active metabolite with proconvulsant properties), mainly by CYP3A4 and CYP2B6. |
| Excretion | Primarily renal (90% as metabolites, ~5-30% unchanged); biliary/fecal excretion accounts for <10%. Urinary excretion is pH-dependent; acidic urine increases elimination. |
| Half-life | Terminal elimination half-life: 2.5–4 hours (mean 3.2 h). In cirrhosis, half-life prolonged to 7–11 hours; in elderly, half-life extends up to 8 hours. Normeperidine (active metabolite) half-life: 15–30 hours (accumulates with renal impairment). |
| Protein binding | 65–75% bound primarily to alpha-1-acid glycoprotein (AAG) and albumin. |
| Volume of Distribution | 2.7–4.2 L/kg. High Vd indicates extensive tissue distribution, including CNS. |
| Bioavailability | Oral: approximately 50–60% (first-pass metabolism); IM/IV: 100%. |
| Onset of Action | IV: 1–2 minutes; IM: 10–15 minutes; Oral: 30–60 minutes (but oral bioavailability is low). |
| Duration of Action | IV/IM: 2–4 hours (analgesia); Oral: 2–4 hours. Normeperidine accumulation may cause prolonged CNS excitation. |
50-100 mg IM/SC every 3-4 hours as needed; 25-50 mg IV slowly every 3-4 hours as needed.
| Dosage form | INJECTABLE |
| Renal impairment | GFR 10-50 mL/min: administer 75% of normal dose every 4-6 hours. GFR <10 mL/min: administer 50% of normal dose every 6 hours. Monitor for neurotoxicity. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: avoid use or reduce dose by 75% with extended interval. |
| Pediatric use | 1-1.5 mg/kg IM/SC/IV every 3-4 hours as needed; maximum single dose 100 mg. Not recommended for prolonged use. |
| Geriatric use | Initiate at 25 mg IM/SC/IV every 4 hours; titrate cautiously due to increased risk of CNS and respiratory depression. Avoid, if possible, due to risk of delirium and falls. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
MAOIs can cause serotonin syndrome and hyperpyrexia Life-threatening respiratory depression may occur.
| Breastfeeding | Enters breast milk in small amounts; M/P ratio approximately 0.5. Use with caution, especially in neonates or preterm infants, due to risk of respiratory depression and withdrawal. AAP considers it compatible with breastfeeding, but alternatives preferred. |
| Teratogenic Risk | FDA Category C. First trimester: limited human data; animal studies show no clear teratogenicity but fetal effects at high doses. Second/third trimester: risk of neonatal respiratory depression, withdrawal, and neurobehavioral effects with chronic or high-dose use near term. |
■ FDA Black Box Warning
Meperidine carries a risk of respiratory depression, particularly in elderly, cachectic, or debilitated patients, and when used in high doses or with other CNS depressants. Concomitant use with CYP3A4 inhibitors or discontinuation of CYP3A4 inducers may increase meperidine exposure. Accidental ingestion, especially in children, can be fatal.
| Common Effects | Sedation |
| Serious Effects |
["Hypersensitivity to meperidine or any component of the formulation","Concurrent use of monoamine oxidase inhibitors (MAOIs) or within 14 days of such therapy","Severe respiratory depression in unmonitored settings or absence of resuscitative equipment","Acute or severe bronchial asthma in unmonitored settings or without resuscitative equipment","Suspected paralytic ileus"]
| Precautions | ["Risk of respiratory depression; use with caution in patients with head injury, increased intracranial pressure, or impaired respiratory function.","Serotonin syndrome risk when used with serotonergic drugs (e.g., SSRIs, MAOIs).","Normeperidine accumulation can cause CNS excitation, seizures, and anxiety; avoid prolonged use or high doses.","Risk of opioid use disorder, abuse, and addiction; monitor for signs of misuse.","Neonatal opioid withdrawal syndrome with prolonged use during pregnancy.","Adrenal insufficiency and androgen deficiency with chronic use.","Severe hypotension in patients with compromised ability to maintain blood pressure.","Use with caution in renal or hepatic impairment, elderly, and cachectic patients.","May impair mental or physical abilities; caution during driving or hazardous tasks."] |
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| Fetal Monitoring | Monitor maternal respiratory rate, sedation, and pain scores. Fetal heart rate monitoring during labor; assess neonatal Apgar scores, respiratory effort, and signs of opioid withdrawal. |
| Fertility Effects | May impair fertility in females via inhibition of GnRH and gonadotropin release; chronic use may cause oligomenorrhea or anovulation. Reversible upon cessation. |