Dutasteride

Generic name: dutasteride
Brand name: Avodart
Dosage form: oral capsule (0.5 mg)
Drug class: 5-alpha-reductase inhibitors

Medically reviewed by A Ras MD.

What is dutasteride?

Dutasteride is a prescription medicine that is used in men to treat the signs of an enlarged prostate. Dutasteride may be given to you for other reasons.

Description

Dutasteride and tamsulosin hydrochloride capsules contain dutasteride (a selective inhibitor of both the type 1 and type 2 isoforms of steroid 5 alpha-reductase, an intracellular enzyme that converts testosterone to DHT and tamsulosin (an antagonist of alpha1A-adrenoceptors in the prostate).

Each dutasteride and tamsulosin hydrochloride capsule contains the following:

One dutasteride opaque white colored, oblong shaped soft gelatin capsules containing clear colorless to slightly yellowish oily liquid, containing 0.5 mg dutasteride and the inactive ingredients: butylated hydroxy toluene, gelatin, glycerin, methylparaben, mono and diglycerides of capric acid, propylparaben and titanium dioxide.
Tamsulosin hydrochloride white to off-white pellets, containing 0.4 mg tamsulosin hydrochloride and the inactive ingredients: microcrystalline cellulose, methacrylic acid copolymer dispersion, talc and triacetin.

The above components are encapsulated in a hard-shell capsule made with the inactive ingredients: carrageenan, hypromellose, iron oxide yellow, potassium chloride, titanium dioxide, and imprinted with black pharmaceutical ink which contains butyl alcohol, ferrosoferic oxide, dehydrated alcohol, isopropyl alcohol, propylene glycol, potassium hydroxide, shellac and strong ammonia solution.

Dutasteride: Dutasteride, USP is a synthetic 4-azasteroid compound chemically designated as (5α,17β)-N-{2,5 bis(trifluoromethyl)phenyl}-3-oxo-4-azaandrost-1-ene-17-carboxamide. The molecular formula of dutasteride is C27H30F6N2O2, representing a molecular weight of 528.5 with the following structural formula:

Dutasteride and tamsulosin hydrochloride capsules

Dutasteride, USP is white to off-white colored powder. It is soluble in absolute ethanol and methanol and insoluble in water.

Tamsulosin: Tamsulosin hydrochloride, USP is a synthetic compound chemically designated as (-)-(R)-5-[2-[[2-(o-Ethoxyphenoxy)ethyl]amino]propyl]-2-methoxybenzenesulfonamide, monohydrochloride.

The molecular formula of tamsulosin hydrochloride is C20H28N2O5S•HCl. The molecular weight of tamsulosin hydrochloride is 444.97. Its structural formula is:

Tamsulosin hydrochloride, USP is white crystalline powder, odorless or practically odorless. It is slightly soluble in water and anhydrous ethanol, sparingly soluble in methanol, freely soluble in dimethyl sulfoxide and formic acid, practically soluble in ether.

Mechanism of Action

Dutasteride and tamsulosin hydrochloride capsules are a combination of 2 drugs with different mechanisms of action to improve symptoms in patients with BPH: dutasteride, a 5-alpha-reductase inhibitor, and tamsulosin, an antagonist of alpha1A-adrenoreceptors.

Dutasteride: Dutasteride inhibits the conversion of testosterone to DHT. DHT is the androgen primarily responsible for the initial development and subsequent enlargement of the prostate gland. Testosterone is converted to DHT by the enzyme 5 alpha-reductase, which exists as 2 isoforms, type 1 and type 2. The type 2 isoenzyme is primarily active in the reproductive tissues, while the type 1 isoenzyme is also responsible for testosterone conversion in the skin and liver.

Dutasteride is a competitive and specific inhibitor of both type 1 and type 2 5-alpha-reductase isoenzymes, with which it forms a stable enzyme complex. Dissociation from this complex has been evaluated under in vitro and in vivo conditions and is extremely slow. Dutasteride does not bind to the human androgen receptor.

Tamsulosin: Smooth muscle tone is mediated by the sympathetic nervous stimulation of alpha1-adrenoceptors, which are abundant in the prostate, prostatic capsule, prostatic urethra, and bladder neck. Blockade of these adrenoceptors can cause smooth muscles in the bladder neck and prostate to relax, resulting in an improvement in urine flow rate and a reduction in symptoms of BPH.

Tamsulosin, an alpha1-adrenoceptor blocking agent, exhibits selectivity for alpha1-receptors in the human prostate. At least 3 discrete alpha1-adrenoceptor subtypes have been identified: alpha1A, alpha1B, and alpha1D; their distribution differs between human organs and tissue. Approximately 70% of the alpha1-receptors in human prostate are of the alpha1A subtype. Tamsulosin is not intended for use as an antihypertensive.

Before taking dutasteride, tell your doctor:

For all patients taking dutasteride:

If you are allergic to dutasteride; any part of this medicine; or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.
If you are a woman. This medicine is not approved for use in women. If you are a woman using dutasteride, talk with your doctor if you are pregnant, plan on getting pregnant, or are breast-feeding.

Children:

If the patient is a child. Do not give dutasteride to a child.

This is not a list of all drugs or health problems that interact with dutasteride.

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take dutasteride with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take dutasteride?

For all patients taking dutasteride:

Tell all of your health care providers that you take dutasteride. This includes your doctors, nurses, pharmacists, and dentists.
Have blood work checked as you have been told by the doctor. Talk with the doctor.
Have a rectal exam (to check prostate gland) and blood work (PSA test). Talk with your doctor.
This medicine may affect certain lab tests. Tell all of your health care providers and lab workers that you take dutasteride.
Do not donate blood while using dutasteride and for 6 months after stopping.
A very bad form of prostate cancer was seen more often in some men taking drugs like this one than in those who were not. This was seen in a trial of men taking these drugs to lower the chance of prostate cancer. Talk with your doctor.
This medicine may affect sperm in men. This may affect being able to father a child. Talk with the doctor.
Pregnant women or females of childbearing age must not touch the capsules. Talk with the doctor.
If a woman who is pregnant or may get pregnant touches a leaking capsule, the area must be washed right away with soap and water. Tell your doctor right away.

Women:

This medicine may cause harm to the unborn baby if you take it while you are pregnant.

How is dutasteride best taken?

Use dutasteride as ordered by your doctor. Read all information given to you. Follow all instructions closely.

Keep taking dutasteride as you have been told by your doctor or other health care provider, even if you feel well.
Take with or without food.
Swallow whole. Do not chew, open, or crush.
Do not take or touch the capsule if it is deformed, changes color, or is leaking.

What do I do if I miss a dose?

Take a missed dose as soon as you think about it.
If it is close to the time for your next dose, skip the missed dose and go back to your normal time.
Do not take 2 doses at the same time or extra doses.

What are the side effects of dutasteride that I need to call my doctor about immediately?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
Enlarged breasts.
Breast pain.
A lump in the breast, breast pain or soreness, or nipple discharge.
Low mood (depression).

What are some other side effects of dutasteride?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

Dizziness.
This medicine may cause a change in sex ability in men or lowered interest in sex. This could go on after you stop dutasteride. Talk with your doctor if these effects go on or bother you.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

If overdose is suspected:

If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

How do I store and/or throw out dutasteride?

Store at room temperature.
Store in a dry place. Do not store in a bathroom.
Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.