Alprostadil
obstetric use
Prostaglandin analogues (obstetric use)
Prostaglandin E1. An infusion keeps the ductus arteriosus open in newborns with duct-dependent heart defects; locally it treats erectile dysfunction.
Also called: Prostaglandin E1, PGE1
Quick facts
- Group
- Prostaglandin analogues (obstetric use)
- Target
- Prostaglandin E receptors (EP2 and EP4, Gs-coupled)
- Used for
- Temporary opening · Duct-dependent systemic
- Key effects
- Newborns · Penile use · Dizziness or fainting
- Monitor
- Newborns · Newborns on long infusions · Penile use
- ATC
- C01EA01
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows prostaglandin E2, which differs from alprostadil (PGE1) by one double bond, in the human EP2 receptor with its Gs protein; no EP-receptor structure with PGE1 is available.
Alprostadil is prostaglandin E1. It activates EP receptors on smooth muscle that raise cAMP and relax the muscle. In the newborn it relaxes the smooth muscle of the ductus arteriosus, which would otherwise close after birth, so blood can keep flowing between the aorta and pulmonary artery while surgery is planned. In the penis it relaxes the arteries and the cavernosal smooth muscle, letting blood fill the erectile tissue. It also dilates other vessels and inhibits platelet aggregation. Most of it is broken down in a single pass through the lungs, so it is given continuously.
- Activates EP receptors: cAMP rises in smooth muscle
- Ductus arteriosus stays open in the newborn
- Penile arteries and cavernosal muscle relax: erection
- Lungs clear most of it in one pass: continuous infusion
Indications
- Temporary opening of the ductus arteriosus in newborns with duct-dependent congenital heart disease, until surgery Transposition of the great arteries →
- Duct-dependent systemic or pulmonary flow (for example hypoplastic left heart, coarctation, tetralogy with pulmonary atresia) Hypoplastic left heart syndrome →
- Erectile dysfunction (penile injection or urethral pellet), and diagnosis of erectile dysfunction Erectile dysfunction →
Adverse effects
Common
- Newborns: fever, flushing, bradycardia or tachycardia, low blood pressure, diarrhoea
- Penile use: pain, bruising or bleeding at the site, burning in the urethra
- Dizziness or fainting
Contraindications
- Newborns: respiratory distress syndrome (it is not used for this)
- Penile use: conditions that predispose to priapism (sickle cell disease, leukaemia, multiple myeloma), penile deformity such as Peyronie disease, penile implant
- Urethral pellet: sex with a pregnant partner without a condom
Key interactions
- Anticoagulants and antiplatelets
- More bleeding (it inhibits platelet aggregation).
- Alcohol
- May reduce the erectile response.
What is monitored
- Newborns: breathing continuously (ventilation ready), arterial blood pressure, temperature, oxygen saturation
- Newborns on long infusions: signs of gastric outlet obstruction
- Penile use: duration of erection; nodules or curvature
Administration and safety
- Neonatal use only in units that can ventilate the baby immediately; diluted before use and given by continuous infusion into a large vein or umbilical artery catheter.
- Fresh dilutions are prepared at regular intervals and old ones discarded; the solution is checked for particles.
- The lowest effective infusion rate is used for the shortest time; the rate is cut at once if pressure falls.
- Penile injection: the first dose is given in the clinic and the patient is trained; needles and syringes are never reused.
Pregnancy and breastfeeding
It is a neonatal and male treatment; with urethral pellets, a condom is used if the partner is or may become pregnant.
Nursing care
- Newborn: keep apnoea monitoring, bag-mask and intubation equipment at the bedside.
- Newborn: record temperature, heart rate, blood pressure and oxygen saturation often.
- Adult: teach to seek urgent care for an erection lasting more than four hours.
- Adult: teach to rotate injection sites and to report lumps or curvature.
Pharmacokinetics
- Absorption
- Neonates: continuous intravenous infusion (or via an umbilical artery catheter). Erectile dysfunction: injection into the penis or a urethral pellet.
- Metabolism
- Very rapid; most is metabolised in one pass through the lungs.
- Elimination
- Metabolites are excreted mainly in the urine.
Test yourself
Think of the answer, then tap the question to see it.
Why is alprostadil infused in a newborn with transposition of the great arteries?
To keep the ductus arteriosus open so that blood can mix until surgery.
What is the boxed warning for alprostadil in newborns?
Apnoea, so it is used only where ventilation is immediately available.
Why must the neonatal infusion be continuous?
Most of the drug is metabolised in one pass through the lungs.
What urgent complication must men using it for erectile dysfunction know about?
Priapism: an erection lasting more than four hours needs emergency care.
Connections
← Back to the class: Prostaglandin analogues (obstetric use)
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: ALPROSTADIL injection, solution, concentrate (DailyMed (U.S. National Library of Medicine), 2026); Alprostadil Urogenital: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2023); Cryo-EM structure of the PGE2-bound EP2-Gs complex (RCSB Protein Data Bank, 2021); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.