(alprostadil)
12 CLINICAL PHARMACOLOGY
12 CLINICAL PHARMACOLOGY
12.1 Mechanism of Action
Alprostadil (PGE1) is a prostaglandin with a wide variety of pharmacological actions including vasodilation and inhibition of platelet aggregation. Alprostadil induces erection by relaxation of trabecular smooth muscle and by dilation of cavernosal arteries by binding to its receptors and increasing intracellular cyclic adenosine monophosphate (cAMP) levels via modulation of adenylate cyclase. This leads to expansion of lacunar spaces and entrapment of blood by compressing the venules against the tunica albuginea, a process referred to as the corporal veno-occlusive mechanism. Alprostadil also attenuates presynaptic noradrenaline release in the corpus cavernosum.
Studies in vitro have shown that alprostadil relaxed isolated preparations of human corpus cavernosum and spongiosum, as well as cavernous arterial segments contracted by either noradrenaline or PGF2α. In pigtail monkeys (Macaca nemestrina), alprostadil increased cavernous arterial blood flow in a dose-dependent manner in vivo.
12.3 Pharmacokinetics
Absorption: For the treatment of erectile dysfunction, alprostadil is administered by injection into the corpora cavernosa. The absolute bioavailability of alprostadil has not been determined.
Distribution: Following intracavernosal injection of 20 mcg alprostadil, mean peripheral plasma concentrations of alprostadil at 30 and 60 minutes after injection (89 picograms/mL and 102 picograms/mL, respectively) were not significantly greater than baseline levels of endogenous alprostadil (96 picograms/mL). Plasma levels of alprostadil were measured using a radioimmunoassay method. Alprostadil is bound in plasma primarily to albumin (81% bound) and to a lesser extent α-globulin IV-4 fraction (55% bound). No significant binding to erythrocytes or white blood cells was observed.
Metabolism: Alprostadil is converted to compounds which are further metabolized prior to excretion. Following intravenous administration, approximately 80% of circulating alprostadil is metabolized in one pass through the lungs, primarily by beta- and omega-oxidation. Following intracavernosal injection of 20 mcg alprostadil, peripheral levels of the major circulating metabolite, 13, 14-dihydro-15-oxo-PGE1, increased to reach a peak 30 minutes after injection and returned to pre-dose levels by 60 minutes after injection.
Excretion: The metabolites of alprostadil are excreted primarily by the kidney, with almost 90% of an administered intravenous dose excreted in urine within 24 hours post-dose. The remainder of the dose is excreted in the feces. There is no evidence of tissue retention of alprostadil or its metabolites following intravenous administration.
PATIENT INFORMATION
Patient Information
CAVERJECT [KAV-er-jeckt]®
(alprostadil)
for injection, for intracavernosal use
Read this Patient Information before you start using CAVERJECT and each time you get a refill. There may be new information. This information does not take the place of talking to your healthcare provider about your medical condition or your treatment.
What is CAVERJECT?
CAVERJECT is a prescription medicine used:
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- to treat erectile dysfunction (ED).
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- with other medical tests to diagnose ED.
CAVERJECT is not meant for use in women or children.
Do not use CAVERJECT if you:
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- are allergic to alprostadil or any of the ingredients in CAVERJECT. See the end of this leaflet for a complete list of ingredients in CAVERJECT
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- have certain medical problems that might cause you to have an erection that lasts for more than 4 hours, such as sickle cell anemia, sickle cell trait, multiple myeloma, leukemia
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- have a deformed penis shape
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- have a penile implant
Before you use CAVERJECT, tell your healthcare provider about all your other medical conditions, especially if you:
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- have had an erection that lasted more than 4 hours
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- have sickle cell trait or sickle cell anemia
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- have or have had a blood cell cancer called multiple myeloma or leukemia
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- have a deformed penis shape
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- have a penile implant
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- have low blood pressure (hypotension)
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- have bleeding problems
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- have or have had heart problems such as a heart attack, irregular heartbeat, angina, chest pain, narrowing of the aortic valve or heart failure
Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.
CAVERJECT may affect the way other medicines work, and other medicines may affect the way CAVERJECT works causing side effects.
Especially tell your healthcare provider if you take any other medicines that are treatments for ED, other medicines injected into your penis (intracavernosally), or certain medicines called anticoagulant medicines (such as heparin or warfarin).
Ask your healthcare provider or pharmacist for a list of these medicines if you are not sure.
Know the medicines you take. Keep a list of them to show to your healthcare provider and pharmacist when you get a new medicine.
How should I use CAVERJECT?
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- See the detailed Instructions for Use that comes with your CAVERJECT for information about how to prepare and inject CAVERJECT the right way.
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- You should receive your first dose of CAVERJECT in your healthcare provider's office.
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- Use CAVERJECT exactly as your healthcare provider tells you to.
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- Your healthcare provider will tell you how much CAVERJECT to use and when to use it.
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- Your healthcare provider may change your dose if needed. Do not change your dose of CAVERJECT without first talking to your healthcare provider.
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- Your healthcare provider should show you how to prepare and inject CAVERJECT the right way before you inject it for the first time.
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- CAVERJECT should not be used more than 3 times per week.
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- CAVERJECT should not be used more than 1 time every 24 hours.
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- Change the exact place and side of the penis that you inject CAVERJECT each time you use it.
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- CAVERJECT is for 1 time use only and should be thrown away properly after each use.
You should see your healthcare provider every 3 months for check-ups to be sure that CAVERJECT is working the right way and to change your CAVERJECT dose if needed.
What are the possible side effects of CAVERJECT?
CAVERJECT may cause serious side effects, including:
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- an erection that will not go away (priapism). If you have an erection that lasts more than 4 hours, get medical help right away. If it is not treated right away, this condition can permanently damage your penis.
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- deformed penis shape (penile fibrosis). Your healthcare provider should check your penis regularly for signs of penile fibrosis. You should not continue to use CAVERJECT if you get penile fibrosis.
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- low blood pressure (hypotension).
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- injection site bleeding. People who take certain medicines called anticoagulants (such as heparin or warfarin) may have a risk for increased bleeding at the injection site.
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- increased risk of heart problems. Sexual activity can put an extra strain on your heart, especially if your heart is weak from a heart attack or heart disease. Ask your healthcare provider if your heart is healthy enough to handle the extra strain of having sex. Stop sexual activity and get medical help right away if you get symptoms of a heart problem such as chest pain, dizziness or nausea.
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- needle breakage. There is a possibility of needle breakage with use of CAVERJECT. To best avoid breaking the needle, you should pay careful attention to your healthcare provider's instructions and handle the syringe and needle properly. If the needle is bent at any time, do not attempt to straighten it and do not use it. A bent and re-straightened needle is more likely to break. If the needle breaks during injection and you are able to see and grasp the broken end, you should remove it and contact your healthcare provider. If you cannot see or cannot grasp the broken end, you should promptly contact your healthcare provider.
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- benzyl alcohol toxicity. Benzyl alcohol is a preservative that is present in CAVERJECT when it is mixed. Benzyl alcohol has caused serious side effects, including death, in children, especially premature and low-birth weight infants, who have received the preservative benzyl alcohol. CAVERJECT is not meant for use in children.
CAVERJECT does not protect you or your partner from getting sexually transmitted infections, including HIV-the virus that causes AIDS.
The most common side effect of CAVERJECT is penile pain
These are not all the possible side effects of CAVERJECT.
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
General information about the safe and effective use of CAVERJECT
Medicines are sometimes prescribed for purposes other than those listed in a Patient Information Leaflet. Do not use CAVERJECT for a condition for which it was not prescribed. Do not give CAVERJECT to other people even if they have the same symptoms that you have. It may harm them.
You can ask your pharmacist or healthcare provider for information about CAVERJECT that is written for health professionals.
What are the Ingredients in CAVERJECT?
Active ingredient: alprostadil
Inactive ingredients: lactose, sodium citrate, benzyl alcohol (contained in the final solution) and hydrochloric acid and/or sodium hydroxide for pH adjustment.
This product's labeling may have been updated. For the most recent prescribing information, please visit www.pfizer.com
LAB-1045-3.0
Revised: March 2023
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