Prostaglandin E1

Absorption

In patients with erectile dysfunction given 20 μg of alprostadil intracavernously, the systemic plasma concentrations of prostaglandin E1 increased from a baseline of 0.8 pg/mL to a Cmax of 16.8 pg/mL (corrected for baseline). The tmax and AUC for this group of patients were 4.8 min and 173 pg?min/mL, respectively. In patients given 20 μg of alprostadil intravenously, AUC was similar to the one detected in patients that received alprostadil intracavernously (174 pg?min/mL); however, they had a higher tmax (25.5 min) and a lower Cmax (7.09 pg/mL). Compared to the same dose given by a short-term intravenous infusion, the absolute bioavailability of alprostadil estimated from systemic exposure was about 98%.

Toxicity

In neonatal patients given alprostadil intravenously, apnea, bradycardia, pyrexia, hypotension, and flushing may be signs of drug overdosage. In patients with apnea or bradycardia, discontinue the infusion, and provide appropriate medical treatment. Caution should be used in restarting the infusion. In patients with pyrexia or hypotension, reduce the infusion rate until these symptoms subside. Flushing is usually a result of incorrect intraarterial catheter placement, and the catheter should be repositioned.
For patients given alprostadil intracavernosally for the treatment of erectile dysfunction, there is limited data on overdosage. Systemic reactions are uncommon with the intracavernous use of alprostadil, and hypotension occurrs in less than 1% of patients treated with this drug. A prolonged erection or priapism is the main symptom of an alprostadil overdose in this group of patients. Erections lasting more than 6 hours should be treated due to the potential for tissue hypoxia and possible necrosis. In the event of an intracavernous overdose, the patient is strongly encouraged to go to the nearest emergency room if his personal physician is not available. Supportive therapy according to the presence of other symptoms is recommended.
The oral LD50 of alprostadil in mice and rats is 186 mg/kg and 228 mg/kg, respectively.

Description

PGE1?(745-65-3) is an endogenous prostaglandin with vasodilatory, anti-platelet, and anti-hypertensive activities.1,2 It is in clinical use for the treatment of erectile dysfunction3 and the emergency management of infants with patent ductus arteriosus4. It has also been used in the treatment of peripheral arterial occlusive disease (PAD).5

Chemical properties

Crystalline Solid

Originator

Alprostadil,Schwarz Pharmacia

The Uses of Prostaglandin E1

A primary Prostaglandin; easily crystallized from purified biological extracts. Vasodilator (peripheral)

The Uses of Prostaglandin E1

Vasodilator;Prostaglandin receptor agonist

The Uses of Prostaglandin E1

For use in cell culture applications for the study of prostaglandin regulated cell signaling and gene regulation.

Background

Alprostadil is a chemically-identical synthetic form of prostaglandin E1 (PGE1), a potent vasodilator produced endogenously. In 1996, the FDA approved the use of alprostadil, administered either with an intracavernosal injection or an intraurethral suppository, for the treatment of erectile dysfunction, and it is used in men for whom oral treatment is either contraindicated or ineffective. After administration, alprostadil promotes smooth muscle relaxation of the corpus cavernosal.
Alprostadil is also used in neonatal patients with congenital heart defects that depend on a patent ductus for survival until corrective or palliative surgery can be performed. This drug causes vasodilation by directly affecting vascular and ductus arteriosus (DA) smooth muscle, preventing or reversing the functional closure of the DA that occurs shortly after birth. This results in increased pulmonary or systemic blood flow in infants.

Indications

Alprostadil is indicated for palliative, not definitive, therapy to temporarily maintain the patency of the ductus arteriosus until corrective or palliative surgery can be performed in neonates who have congenital heart defects and who depend upon the patent ductus for survival. It is also indicated for the treatment of erectile dysfunction due to neurogenic, vasculogenic, psychogenic, or mixed etiology, and as an adjunct to other diagnostic tests in the diagnosis of erectile dysfunction.

What are the applications of Application

PGE1 (Prostaglandin E1) is a major prostaglandin that affects protein kinase C (PKC), calcium movement, and adenylate cyclase

Indications

Alprostadil (prostaglandin E₁ [PGE₁]; Edex, Topiglan) exerts a number of effects, including systemic vasodilation, inhibition of platelet aggregation, and stimulation of intestinal motility. PGE₁ relaxes isolated smooth muscle cells contracted by norepinephrine. It has become widely used in the treatment of ED. Alprostadil binds with PGE receptors and results in a cyclic adenosine monophosphate (cAMP) mediated smooth muscle relaxation. Little is known about the pharmacokinetics of PGE₁, but it is believed that as much as 80% is metabolized in one pass through the lungs. Such rapid degradation probably accounts for its lack of significant cardiovascular side effects when administered intracavernosally. PGE₁ can also be metabolized in the penis.

Definition

ChEBI: Prostaglandin E1 is a prostaglandins E. It has a role as a platelet aggregation inhibitor, a vasodilator agent, an anticoagulant and a human metabolite. It is a conjugate acid of a prostaglandin E1(1-).

brand name

Caverject (Pfizer); Caverject (Pharmacia & Upjohn); Edex (Schwarz Pharma); Muse (Vivus); Prostin (Pharmacia & Upjohn);Coverject;Minprog pad;Postivas;Prostadin;Prostalgin;Prostandin;Prostavasin;Prostin vr pediatric;Prostin-vr;Prostivas.

Therapeutic Function

Vasodilator, Abortifacient, Antihypertensive, Bronchodilator

World Health Organization (WHO)

Alprostadil, a prostaglandin with vasodilating and platelet antiaggregatory activity, was introduced in 1984 for the treatment of chronic arterial obstruction. Intravenous administration of the drug has been associated with adverse effects that have sometimes been severe. These include allergic reactions, pulmonary oedema and cardiac insufficiency. Interactions with antihypertensive agents, vasodilators, anticoagulants and inhibitors of platelet aggregation have also occurred. This has led the German agency to modify the approved product information of alprostadil preparations to warn against these adverse effects.

Biological Functions

Prostaglandin E1 is produced endogenously to relax vascular smooth muscle and cause vasodilation by activating the adenylate cyclase/cAMP pathway. Recent studies show that the cAMP is important in the PGE1 relaxation of penile erectile tissue and vasodilation of penile resistance arteries. Moreover, agents that stimulate the release of cAMP also crossactivate the NO/cGMP cascade.

General Description

PGE1, Alprostadil (Prostin VR Pediatric), is a naturally occurring prostaglandin that has found particular use in maintaining a patent (opened) ductus arteriosus in infants with congenital defects that restrict pulmonary or systemic blood flow.
Alprostadil must be administered intravenously continually at a rate of approximately 0.1 μg/kg/min to maintain the patency of the ductus arteriosus until corrective surgery can be performed. Up to 80% of circulating alprostadil may be metabolized in a single pass through the lungs. Because apnea has been observed in 10% to 12% of neonates with congenital heart defects, this product should be administered only when ventilatory assistance is immediately available. Other commonly observed side effects include decreased arterial blood pressure, which should be monitored during infusion; inhibited platelet aggregation, which might aggravate bleeding tendencies; and diarrhea.

Biological Activity

Prostaglandin with some selectivity for EP 3 and EP 4 receptors (K i values are 1.1, 2.1, 36, 10? and 33 nM for mouse EP 3 , EP 4 , EP 1 , EP 2 and IP receptors respectively). Inhibits platelet aggregation and is a vasodilator in vivo .

Biochem/physiol Actions

Prostaglandin E1?(PGE1) aids in the relaxation of corporal cavernosal tissue. It helps to preserve the patency of the ductus arteriosus. It is used to treat erectile dysfunction (ED).

Mechanism of action

PGE₁ is not orally effective. Its therapeutic success depends on its being injected intracavernosally or administered transurethrally or intraurethrally. PGE₁ has also been used in combination with other agents, such as papaverine. The injection does not appear to produce any long-term side effects on penile smooth muscle. Transurethral therapy with alprostadil, such as MUSE (alprostadil urethral suppository or medicated urethral system for erection) is also an effective therapeutic technique, and there may be a role for this form of administration in selected patients with ED.The intracavernosal injection of alprostadil (e.g., alprostadil alfadex; Edex, Viridal) is safe and effective in patients with ED when sildenafil is ineffective. Both of these delivery systems have been used in the treatment of ED. MUSE can also be used in conjunction with a penile constrictor device (e.g., ACTIS).

Pharmacokinetics

Prostaglandin E1 is produced endogenously to relax vascular smooth muscle and cause vasodilation. As a synthetic form of prostaglandin E1, alprostadil has the same pharmacodynamic effects. Alprostadil inhibits platelet aggregation, has anti-inflammatory effects, interferes with immune responses, and stimulates factor X, a blood coagulation enzyme.
In adult males, the use of alprostadil may lead to prolonged erection and priapism, penile fibrosis, hypotension, and injection site bleeding. In patients treated up to 24 months with alprostadil, the incidence of prolonged erections (>4 hours long) was 4% of all, and the incidence of priapism (erections greater than 6 hours in duration) was <1%. Patients with preexisting cardiovascular disease treated with alprostadil may also have higher cardiac risk. Neonates with congenital heart defects treated with alprostadil may experience apnea. Apnea is experienced by 10-12% of neonates and is more common in those weighing less than 2 kg at birth. The administration of alprostadil to neonates may also result in gastric outlet obstruction secondary to antral hyperplasia.

Clinical Use

Prostaglandin E1 (PGE1; Alprostadil) is approved for the intracavernosal (Caverject, Edex)or intraurethral suppository (Muse) treatment of ED. A three-drug combination of PGE1, papaverine, and phentolamine sometimes is used as an intracavernosal injection to achieve a synergistic action. Erectile dysfunction that is medication-induced or caused by endocrine problems, such as hypogonadism or hyper- or hypothyroidism, should be evaluated and appropriately treated before PGE1 treatment is considered.

Metabolism

Alprostadil is rapidly metabolized in the human body. Following intracavernous administration, alprostadil is metabolized in the corpus cavernosum, and a smaller portion is absorbed from the penis into systemic circulation. After intravenous or arterial administration, alprostadil is metabolized and distributed throughout the entire body except for the central nervous system. As much as 60-90% of the circulating alprostadil may be metabolized in the lungs through first-pass pulmonary elimination, in a process known as beta- and omega-oxidation.
The enzymatic oxidation of the C15-hydroxy group of alprostadil leads to the formation of 15-keto-PGE1, while the reduction of the C13, 14-double bond produces 15-keto-PGE0, and 13,14-dihydro-PGE1 (PGE0). The 15-keto metabolites are inactive, but the PGE0 metabolite has a similar potency to alprostadil in isolated animal organs. The major metabolite of alprostadil is 15-keto-PGE0.

Metabolism

The major route of excretion of PGE1 metabolites is via the kidney. Its elimination half-life is 5 to 10 minutes. If any alprostadil is systemically absorbed, it is metabolized by a single pass through the lungs. The onset of action is within 10 minutes, and the time to peak effect is less than 20 minutes. The duration of action is 1 to 3 hours for the intracavernosal injection and 30 to 60 minutes for the intraurethral suppository.

storage

Store at -20°C

References

1) Kirtland (1988) Prostaglandin E1: 1 review; Prostaglandins Leukot. Essent. Fatty Acids,?32 165 2) Schermuly et al. (2005) Prostanoids and Phosphodiesterase Inhibitors in Experimental Pulmonary Hypertension; Curr. Top. Dev. Biol. 67 251 3) Urciuoli et al (2004) Prostaglandin E1 for treatment of erectile dysfunction; Cochrane Database Syst. Rev. CD001784 4) Huang et al. (2013) Reappraisal of the prostaglandin E1 dose for early newborns with patent ductus arteriosus-dependent pulmonary circulation; Pediatr. Neonatol. 54 102 5) Schroer and Hohlfeld (2004) Mechanisms of anti-ischemic action of prostaglandin E1 in peripheral arterial occlusive disease; Vasa 33 119