Generic Name

Oxtella XR

Mechanism

• Selective activation of oxytocin receptors (OTRs) on myometrial smooth muscle and mammary gland epithelial cells.
• Gq‑protein coupled signaling → phospholipase C activation → inositol‑1,4,5‑trisphosphate (IP₃) surge → intracellular Ca²⁺ release.
• Ca²⁺‑mediated contraction of the uterus, and stimulation of milk‑ejecting myoepithelial cells.
• The extended‑release matrix slowly liberates peptide to maintain plasma concentrations within the therapeutic window (≈1–6 µg/L) over 24 h, reducing peak‑trough variability common with standard oxytocin.

Pharmacokinetics

*Steady‑state achieved after ~12 h; accumulation factor ≈1.5.*

Indications

• Primary prevention of postpartum hemorrhage (PPH) in women with risk factors (multiple gestation, prolonged labor).
• Management of uterine atony following delivery or miscarriage.
• Induction or augmentation of labor when fetal well‑being permits.
• Breastfeeding support: promotes milk let‑down in lactating mothers with impaired supply.

Contraindications

• Absolute contraindication: known hypersensitivity to oxytocin or any component.
• Relative contraindication:
• Uncontrolled systemic hypertension or pre‑eclampsia.
• Severe cardiovascular or valvular disease.
• Uncorrected electrolyte abnormalities (e.g., hyponatremia).
• Active severe uterine infection (endometritis).
• Warnings:
• Risk of *uterine rupture* in scarred uterus or at ≥ 34 weeks gestation.
• Fluid overload in cardiac or renal failure.
• Hypotension and reflex tachycardia in high doses.

Dosing

• XR infusion: Use a volumetric pump; administer over 24 h with continuous glucose‑containing fluid to maintain osmolarity.

Adverse Effects

• Common (≥5 %)
• Uterine cramping, nausea, vomiting
• Headache, flushing
• Hypotension (mean arterial pressure ↓ 10 mm Hg)
• Mild edema of extremities
• Serious (≤1 %)
• Uterine rupture or perforation
• Severe hypotension requiring vasopressors
• Hyponatremic seizures (if hyper‑fluid intake)
• Ovarian hyperstimulation syndrome (in IVF settings)
• Allergic reaction: rash, bronchospasm, anaphylaxis

Monitoring

• Hemodynamic: BP, heart rate continuously for first 2 h.
• Uterine tone: vaginal exam every 30 min until firm.
• Fetal heart rate: continuous during induction.
• Serum electrolytes: Na⁺, K⁺, Cl⁻; check at baseline, 6 h, then 12 h for at-risk patients.
• Renal function: BUN/creatinine if CRF present.
• Blood loss: estimated units of blood via calibrated drips or hemoglobin/hematocrit drop.

Clinical Pearls

• Peak‑trough mitigation: Use the XR formulation immediately after initial rapid infusion to stabilize uterine contraction and reduce cumulative dose.
• Combined therapy: Pair with misoprostol (≤ 800 µg) for maximal uterotonic effect in high‑risk PPH without increasing oxytocin dose.
• Fluid management: Maintain isotonic crystalloid (e.g., lactated Ringer’s) to counteract fluid shift and hyponatremia risk.
• Lactation: Early administration (within 30–60 min of placenta delivery) optimizes milk let‑down and reduces infant hypocalcemia risk.
• Cardiac patients: Start at low dose (5 units) and titrate slowly; consider continuous IV infusion rather than bolus.
• Drug interactions: Reduced efficacy when co‑administered with high‑dose antitussives (diphenhydramine), β‑blockers (mitigate tachycardia).

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