Alprostadil - Indications, Side Effects, and Pharmacological Aspects

Overview:

Men with certain types of erectile dysfunction (ED), which is defined by the inability to achieve or maintain an erection, are treated with Alprostadil, which is available as an injectable and a suppository form. The injection version is also used with additional diagnostic procedures to assess ED. Alprostadil is a vasodilator that eases the tension in the blood vessels and muscles of the penis, allowing sufficient blood flow to support an erection. It is important to understand that Alprostadil does not increase sexual desire or treat ED; rather, it helps get an erection. Moreover, it is ineffective as a means of contraception and does not stop the spread of sexually transmitted infections like HIV (human immunodeficiency virus). The United States Food and Drug Administration approved Alprostadil in 1981.

Drug Group:

Alprostadil belongs to a group of drugs known as vasodilators.

Available Doses and Dosage Forms:

• Erectile Dysfunction of Vasculogenic, Psychogenic, or Mixed Etiology

  • Start treating erectile dysfunction with 2.5 mcg (microgram) of Alprostadil.

  • Increase the dose to five micrograms if partial response is seen after one hour.

  • Do not provide more than two doses in 24 hours. Use a fresh vial for every dosage.

  • The goal is to obtain an erection long enough for sexual activity and should not exceed more than one hour.

  • The patient must stay in the doctor's office until they fully recover from shock.

  • If additional titration is required, dosages can be raised by five to ten microgram increments, with a minimum of 24 hours between each delivery. Titration is recommended until the optimal dose is reached instead of exceeding 60 mcg.

• Erectile Dysfunction Caused by Neurogenic Factors Like Spinal Cord Injury

  • The initial dose of 1.25 mcg of Alprostadil is administered.

  • If a partial response is seen, the dose can be increased to 2.5 mcg after one hour. It is essential to use a fresh vial every time.

  • It is recommended to administer no more than two doses in 24 hours while titrating.

  • An ideal dosage should result in an erection that lasts no longer than an hour and is appropriate for sexual activity.

  • Until total detumescence (erection loss), the patient has to remain in the doctor's office.

  • Within the next 24 hours, a dose of 5 mcg may be administered if further titration is needed.

  • Afterward, until the ideal dose is obtained, doses may be administered at least 24 hours apart in increments of 5 mcg. Doses higher than 60 mcg are not advised.

• Maintenance Dosage for At-Home Use by Patients: After determining the right dosage of Alprostadil in a clinical setting, additional changes by the titration instructions could be required after speaking with the doctor. Injections should only be given up to three times each week, with a minimum of 24 hours between doses. Patients should be reevaluated regularly, ideally every three months or more frequently as clinically necessary, to see whether dosage adjustments are necessary.

For Patients:

What Is Erectile Dysfunction?

Erectile dysfunction, or ED, is the most common sexual ailment that men report to their doctor. ED is defined as difficulty getting or keeping an erection adequate for sexual engagement. Men occasionally experience problems getting an erection, but ED that worsens or recurs regularly during sexual conduct is unusual and should be addressed.

How Does Alprostadil Work?

Alprostadil treats erectile dysfunction. It is a member of the class of drugs known as vasodilators, which dilate blood vessels to improve blood flow. This medicine works by increasing blood flow to the penis, which results in an erection.

What Are the Things to Inform the Doctor Before Taking Alprostadil?

• When using Alprostadil, people should let their doctor know if they have any allergies to the drug or any other related medications. This includes prostaglandins like Travoprost, Bimatoprost, Latanoprost, and Misoprostol. In addition, since dosage adjustments might be required, they should reveal all current medications, prescription and over-the-counter, as well as any supplements and herbal products.

• Any medical concerns should be discussed with the doctor, particularly those of cardiovascular health, blood diseases, penile conditions, or recent surgeries. In addition, people should let their doctor know if they or their partner want to get pregnant since certain safety measures must be taken.

• Alprostadil may cause dizziness and fainting; therefore, until the medication's effects are established, patients should avoid doing things like driving or operating machinery. Alcohol use should be discussed with the doctor since it may reduce the efficacy of the prescription.

• People should be informed that bleeding may occur at the site of medicine administration, which could raise the possibility of spreading blood-borne illnesses to their partners. Talking about this risk with the doctor is advised, particularly if one or both partners have a blood-borne illness.

How Is Alprostadil Administered?

Alprostadil is available in two forms: a urethral suppository (pellet) that is placed into the penis's urinary opening and a powder that is mixed with a liquid and injected into the penis. Before engaging in sexual activity, it is used as needed.

An erection can happen five to twenty minutes after injection, although an erection from a pellet usually happens five to ten minutes. It is anticipated that the erection would last between thirty and sixty minutes. While the pellets should not be used more than twice in 24 hours, the Alprostadil injection should not be used more than three times per week with at least 24 hours in between usage.

Doctors usually give the initial doses in a clinical setting to establish the proper dosage. Once patients begin using Alprostadil at home, doctors may progressively change the dosage based on their response. If a patient experiences unsatisfactory or prolonged erections, they should discuss this with their doctor; however, they should not change the dosage without first seeing a medical practitioner.

To ensure effective administration, patients using Alprostadil at home must receive the necessary training from their physician. It is critical to comprehend the proper usage instructions and seek clarification from a healthcare professional in case of any doubt.

As directed by a physician or nurse, it is critical to use the appropriate needle and enter it perpendicular to the long axis of the penis to reduce the danger of needle fracture.

Needles, syringes, cartridges, vials, pellets, and applicators are disposable items that should never be reused. Following a doctor's or pharmacist's directions, needles and syringes should be disposed of in a puncture-resistant container.

Dietary Instructions: Maintain the same diet unless advised otherwise by the doctor.

Side Effects:

• Adverse reactions to Alprostadil could occur. Inform the doctor if any of the symptoms mentioned below are severe or persistent.

  • Pain or hurting in the legs, testicles, penis, or perineum (the region between the penis and the rectum).

  • Bleeding or bruises where one has applied the drug.

  • Warmth or burning feeling at the urethral opening of the penis.

  • Redness in the penis.

  • Lightheadedness

  • Rash.

• Certain adverse effects may be dangerous. Call the doctor right away if one has any of these symptoms, or seek emergency care:

  • More than four hours of an erection.

  • Swelling of the veins of the legs.

  • Redness, discomfort, swelling, or an odd curvature of the penis while it is erect.

  • Broken needle in the penis.

  • Hard spots or nodules on the penis.

  • Rapid heartbeat.

  • Dizziness.

Missed Dose: No missed doses, as Alprostadil is used when needed.

Overdose: In the event of an overdose of Alprostadil, the patient needs to be continuously watched by a doctor until the loss of erection, known as penile detumescence, has happened or until any other systemic effects have subsided. Treatment should be given if systemic symptoms, such as hypotension (low blood pressure), appear. Overdosage symptoms can include

• Dizziness and fainting.

• Blurry vision.

• Nausea.

• Penis pain that does not go away.

• An erection that lasts more than six hours

Supply and Storage:

Pellets of Alprostadil can be stored for up to 14 days at room temperature, but they should be kept in the refrigerator in their original packaging. The drug will become useless if it is exposed to extreme temperatures or placed in the sun.

Alprostadil injection is a lyophilized powder that comes in vials containing either 23.2 or 46.4 mcg (microgram) of Alprostadil. It is administered in doses of 20 or 40 mcg after reconstitution with one milliliter of bacteriostatic water for injection preserved with benzyl alcohol 0.945 percent w/v (weight by volume). The deliverable amount of Alprostadil is 20 or 40 micrograms, respectively, when reconstituted and used as prescribed. The constitution of Alprostadil should only be done with bacteriostatic water for injection that has been preserved with benzyl alcohol (0.945 percent w/v).

• For 20 mcg vial:

  • Maintain storage between 20°C (degree Celsius) and 25°C (68°F or 68 degrees Fahrenheit and 77°F).

  • Store the reconstituted solution at or below 25°C (77°F) for up to 24 hours. Do not freeze or refrigerate.

• For 40 mcg vial:

  • Before dispensing, keep the product between two degrees Celsius and eight degrees Celsius (36° and 46°F).

  • Upon dispensing, vials must be kept at or below 25°C (77°F) for three months or until the expiration date, whichever comes first.

  • Store the reconstituted solution at or below 25°C (77°F) for up to 24 hours. Do not freeze or refrigerate.

For Doctors:

Indication -

• It is recommended to treat erectile dysfunction.

• When diagnosing erectile dysfunction, Alprostadil is recommended to be used in addition to other diagnostic procedures.

• Alprostadil can also keep the ductus arteriosus (blood vessel of the heart) open until surgery can be performed.

Contraindication -

• Those who have hypersensitivity to Alprostadil or any other ingredient in the dosage form should not use Alprostadil.

• Patients with specific medical diseases such leukemia (blood cancer), polycythemia vera (blood cancer where too many red blood cells are produced), thrombocythemia (excessive platelet production by bone marrow), sickle cell disease or trait, multiple myeloma (malignancy of the plasma cells), or sickle cell disease (red blood cells turns sickle shape) should exercise caution as these conditions can increase the risk of priapism, which Alprostadil may intensify.

• The use of Alprostadil intraurethral suppository in patients with urethral strictures (causes scarring that causes the urethra, the tube that exits the body carrying urine, to narrow) should be avoided as it may result in additional penis damage. Similarly, in patients with urethritis (inflammation of the urethra), doctors should proceed with caution when contemplating Alprostadil as an intraurethral suppository.

• Alprostadil should not be taken by people who have Peyronie's disease (fibrosis of the penis) since it may exacerbate penile fibrosis.

What Are the Pharmacological Aspects of Alprostadil?

• Mechanism of Action - Alprostadil, a prostaglandin E1 (PGE1) synthetic, acts on the body in several ways. Through its interaction with prostaglandin receptors, particularly EP2, it initiates a cascade (adenylate cyclase) that builds cyclic adenosine monophosphate (3 '5'-cAMP). Smooth muscle relaxation brought on by this build-up of cAMP results in bronchodilation and vasodilation, or increased blood flow in the peripheral, which is beneficial for disorders like erectile dysfunction. Alprostadil also inhibits the aggregation of platelets by preventing them from clumping together.

• Pharmacokinetics -

  • Absorption - The drug Alprostadil is injected into the corpora cavernosa to treat erectile dysfunction. Alprostadil's exact bioavailability has not been established, though.

  • Distribution - At 30 and 60 minutes after intracavernosal injection of 20 mcg (microgram) of Alprostadil, the mean peripheral plasma concentrations were 89 and 102 picograms/milliliter (ml), respectively. These values did not substantially surpass the baseline levels of endogenous Alprostadil (96 picograms/mL). A radioimmunoassay technique was used to measure plasma levels. Alprostadil's most common binding sites are albumin (81 percent bound) and the α-globulin IV-4 fraction (55 percent bound). No significant binding to erythrocytes or white blood cells was found.

  • Metabolism - Alprostadil undergoes breakdown to produce substances that are further processed before excreted. The lungs metabolize around 80 percent of the Alprostadil in circulation in a single pass. Thirty minutes after the intracavernosal injection, the main circulating metabolite, which is 13, 14-dihydro-15-oxo-PGE1 reaches its peak level and takes sixty minutes to recover to pre-dose levels.

  • Excretion - The kidneys are primarily responsible for the excretion of Alprostadil metabolites, with approximately 90 percent of an intravenous dose being eliminated in the urine within 24 hours of administration. The residual amount of the medication is eliminated through the feces. After intravenous injection, there is no indication that Alprostadil or its metabolites are retained in the tissue.

• Toxicity (Carcinogenesis, Mutagenesis, and Infertility): Although there have not been any long-term carcinogenicity studies, the information that is now available indicates that Alprostadil does not interfere with rat spermatogenesis or show any mutagenic or genotoxic effects at dosages that are far greater than those used in humans.

Warnings and Precautions:

• Prolonged Erection and Priapism: Prolonged erections, or priapism, are possible side effects of Alprostadil. For erections that last longer than four hours, get medical assistance immediately to avoid damaging penile tissue and for irreversible erection loss. Furthermore, avoid using Alprostadil in individuals with sickle cell anemia, leukemia, or multiple myeloma, as these illnesses can make a patient more susceptible to priapism.

• Penile Fibrosis: Regular physical examinations of the penis are recommended to check for indications of penile fibrosis. Patients should stop taking Alprostadil if they experience penile angulation or cavernosal fibrosis.

• Hypotension: Increased peripheral blood levels of Alprostadil can lead to hypotension. Therefore, caution is advised when administering Alprostadil, especially in patients with known cavernosal venous leakage.

• Bleeding at Injection Site: Patients using anticoagulants, such as Heparin or Warfarin, may be more susceptible to injection site bleeding after receiving an Alprostadil injection.

• Cardiovascular Risk Related to Underlying Medical Conditions: Treating erectile dysfunction with medications such as Alprostadil should be done with caution because there is a risk to the heart from sexual activity, especially in those who already have cardiovascular disease. In males whose cardiovascular condition makes sexual activity contraindicated, it is generally advised to forgo using such treatments.

• Serious Adverse Reactions from Benzyl Alcohol Preservative: When Alprostadil is reconstituted with the suggested diluent, it contains benzyl alcohol, a preservative. It can cause serious and even fatal reactions, especially in newborns and low birth weight babies. Among these reactions is "gasping syndrome," which manifests as respiratory distress, metabolic acidosis, and depression of the central nervous system. For this reason, Alprostadil is not meant for use in newborns or neonates.

• Needle Breakage: Different needles are needed to reconstitute and administer Alprostadil. The superfine needle that is used to distribute it has a chance of breaking. There have been reports of needle breakage, sometimes resulting in a piece remaining in the penis and requiring surgical removal and hospitalization.

• Counseling Regarding Protection Against STDs: There is no protection against sexually transmitted infections (STDs) with Alprostadil, and hence, patients should be informed about the same.

Drug Interaction:

There has not been much research done on the possibility of pharmacokinetic drug-drug interactions between Alprostadil and other medications, whether taken orally or intravenously.

Clinical Studies:

Three distinct study investigations involving men with various causes of erectile dysfunction examined the effects of the drug Alprostadil. These investigations aimed to determine the safety and effectiveness of Alprostadil.

• Different doses of Alprostadil were compared to a placebo in research including 296 males. It was discovered that all dosages of Alprostadil helped men attain erections more effectively than the placebo. The greater the Alprostadil dose, the more effective it is.

• A second research, including 201 men, sought to determine the lowest Alprostadil dosage that was beneficial. It was found that a very modest dose (equivalent to or less than two micrograms) was sufficient for a considerable number of men with diverse causes of erectile dysfunction.

• Most men were able to have successful sex after receiving Alprostadil injections, according to a bigger study that included 683 men who self-administered the shots over six months.

• Some adverse consequences were observed, though. Only a tiny fraction of injections caused mild penile pain, which affected almost half of the males. Five percent of the males reported having extended erections, and one percent experienced priapism, which is characterized by a painful and persistent erection. Less frequently seen side effects included hematomas, bruising, and penile fibrosis.

• The research found that an intracavernosal injection of Alprostadil is a reasonably safe and effective treatment for erectile dysfunction.

Specific Considerations:

• Pregnancy: Alprostadil is not indicated for use in females.

• Lactation: It is not recommended to use Alprostadil on females.

• Pediatric Patients: Safety and efficacy have not been demonstrated in pediatric patients.

• Geriatric Patients: A total of 341 participants who were 65 or older were included in clinical investigations. These subjects did not show any overall changes in safety or effectiveness from younger subjects, and the other reported clinical experience did not find any variations in reactions between older and younger patients.