Adult: Initially, 2.5 mcg, followed by 5 mcg if there is partial response or 7.5 mcg if there is no response. Subsequent increments of 5-10 mcg are given until suitable dose is reached. Usual dose range: 5-20 mcg. Max: 60 mcg. For neurogenic origin (e.g. spinal cord injury): Initially, 1.25 mcg, followed by 2.5 mcg then 5 mcg, and subsequent increments of 5 mcg until suitable dose at intervals of at least 1 day for responders; for non-responders, a higher dose may be given w/in 1 hr. Max frequency: once daily; 3 times wkly.
Intravenous Maintenance of patency of ductus arteriosus in neonates with congenital heart disease
Child: Initially, 0.05-0.1 mcg/kg/min via continuous infusion, reduced to the lowest possible dosage that maintains the response. If response is inadequate, may be increased up to 0.4 mcg/kg/min.
Topical/Cutaneous Erectile dysfunction
Adult: As cream: Initially, 300 mcg is applied to the tip of the penis, may be reduced to 200 mcg if patient cannot tolerate AR. Max frequency: once daily; 2-3 times wkly.
Urethral Diagnosis of erectile dysfunction
Adult: 500 mcg as a single dose.
Urethral Erectile dysfunction
Adult: Initially, 250 mcg, may be increased in stepwise manner to 1,000 mcg; or reduced to 125 mcg according to response. Max frequency: twice daily; 7 doses wkly.
Reconstitution
Soln for IV inj: Dilute w/ NaCl 0.9% or dextrose 5% inj to provide a soln containing 2-20 mcg/mL, depending on the controlled-infusion device employed and the needs of the neonate. Powd for intracavernosal inj: Dilute w/ bacteriostatic or sterile water according to manufacturer’s instructions.
Contraindications
History of recurrent priapism, sickle cell anaemia or trait, multiple myeloma, leukaemia, thrombocythaemia, polycythaemia, predisposition to venous thrombosis, anatomical penile deformation (e.g. angulation, cavernosal fibrosis, Peyronie’s disease, stenosis of distal urethra, severe hypospadias and curvature, balanitis, acute/chronic urethritis), penile implants. Patient for whom sexual activity is inadvisable (e.g. unstable CV or cerebrovascular conditions). Concomitant use w/ other drugs for erectile dysfunction (e.g. phosphodiesterase type 5 (PDE5) inhibitors, papaverine). Neonates w/ resp distress syndrome. Childn (intracavernosal).
Special Precautions
Patient w/ bleeding tendencies, blood-borne and pulmonary diseases, transient ischaemic attacks, CHD, CHF, history of psychiatric disorder or addiction. Pregnancy (use condom barrier if female partner is or may be pregnant).
Adverse Reactions
Headache, flushing, hypotension, diarrhoea; pain, haematoma, and ecchymoses at inj site; pain during erection, fibrotic nodules, Peyronie’s disease, priapism. Rarely, penile fibrosis. Apnoea, fever, bradycardia, tachycardia, convulsion, oedema, cardiac arrest, hypokalaemia, disseminated intravascular coagulation, cortical proliferation of long bones (childn).
This drug may cause dizziness, syncope, and hypotension, if affected, do not drive or operate machinery.
Monitoring Parameters
Monitor for BP, resp and heart rates, temp, degree of penile pain, duration of erection, adequate detumescence after dosing, and signs of infection.
Overdosage
Symptoms: Hypotension, syncope, dizziness, persistent penile pain, priapism, hypertensive crisis. Management: Symptomatic and supportive treatment. Management of prolonged erection or priapism may include aspiration of cavernosal blood or intracavernosal admin of α-adrenergic agonist (e.g. phenylephrine, epinephrine) or dopamine.
Drug Interactions
Reduced effect w/ sympathomimetics, decongestants, and appetite suppressants. May enhance the effects of antihypertensives, vasoactive drugs, anticoagulants and platelet aggregation inhibitors. Potentially Fatal: Enhanced AR, including prolonged erections, w/ PDE5 inhibitors (e.g. sildenafil, tadalafil, vardenafil) and other drugs that induce erection (e.g. papaverine).
Action
Description: Mechanism of Action: Alprostadil, a naturally occurring prostaglandin E1, is a vasodilating agent and a platelet aggregation inhibitor. It induces erection by relaxation of the trabecular smooth muscles and dilation of cavernosal arteries, allowing blood flow to the lacunar spaces of the penis. It also relaxes the smooth muscles of the ductus arteriosus. Onset: Erectile dysfunction: 5-20 min. Duration: Erectile dysfunction: <1 hr. Pharmacokinetics: Absorption: Time to peak plasma concentration: 30-60 min (intracavernosal); approx 16 min (urethral). Distribution: Plasma protein binding: 81%, mainly to albumin; 55% to α-globulin IV-4 fraction. Metabolism: Metabolised (approx 70-80%) in a single pass through the lungs via β- and omega-oxidation into 13,14-dihydro-PGE1, 15-keto-PGE1, and 15-keto-13,14-dihydro-PGE1 (IV). Excretion: Via urine (90% as metabolites) and faeces. Elimination half-life: 0.5-10 min.
Chemical Structure
Alprostadil Source: National Center for Biotechnology Information. PubChem Database. Alprostadil, CID=5280723, https://pubchem.ncbi.nlm.nih.gov/compound/Alprostadil (accessed on Jan. 20, 2020)
Storage
Soln for IV inj/cream/urethral stick: Store between 2-8°C. Do not freeze. Powd for intracavernosal inj: Store below 25°C (5, 10, 20 mcg); 2-8°C (40mcg).
G04BE01 - alprostadil ; Belongs to the class of drugs used in erectile dysfunction. C01EA01 - alprostadil ; Belongs to the class of prostaglandins used in cardiac therapy.
References
Alprostadil Injection, Solution, Concentrate (Teva Parenteral Medicines, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 8/23/2016.Anon. Alprostadil. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 8/23/2016.Buckingham R (ed). Alprostadil. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 8/23/2016.Caverject Injection, Powder, Lyophilized, for Solution (Pharmacia and Upjohn Company LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 8/23/2016.Joint Formulary Committee. Alprostadil. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 8/23/2016.McEvoy GK, Snow EK, Miller J et al (eds). Alprostadil. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 8/23/2016.
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