Darifenacin

Generic name: darifenacin
Brand name: Enablex
Dosage form: tablet, extended release (15 mg; 7.5 mg)
Drug class: Urinary antispasmodics

Medically reviewed by  A Ras MD.

What is darifenacin?

Darifenacin is a prescription medicine that is used to treat an overactive bladder.

Description

Darifenacin extended-release tablets are an extended-release tablet for oral administration which contains 7.5 mg or 15 mg darifenacin as its hydrobromide salt. The active moiety, darifenacin, is a potent muscarinic receptor antagonist.

Chemically, darifenacin hydrobromide is (S)-2-{1-[2-(2,3-dihydrobenzofuran-5-yl)ethyl]-3-pyrrolidinyl}-2,2-diphenylacetamide hydrobromide. The molecular formula of darifenacin hydrobromide is C28H30N2O2•HBr.

The structural formula is:

Darifenacin hydrobromide is a white to off-white, crystalline powder, with a molecular weight of 507.5.

Darifenacin extended-release tablets are a once-a-day extended-release tablet and contains the following inactive ingredients: hypromellose, lactose monohydrate, anhydrous dibasic calcium phosphate, magnesium stearate, titanium dioxide, polydextrose, talc, maltodextrin, medium chain triglycerides (vegetable).The 15 mg tablet also contains red iron oxide non-irradiated, yellow iron oxide non-irradiated and black iron oxide non-irradiated.

Mechanism of Action

Darifenacin is a competitive muscarinic receptor antagonist. Muscarinic receptors play an important role in several major cholinergically mediated functions, including contractions of the urinary bladder smooth muscle and stimulation of salivary secretion.

In vitro studies using human recombinant muscarinic receptor subtypes show that darifenacin has greater affinity for the M3 receptor than for the other known muscarinic receptors (9- and 12-fold greater affinity for M3 compared to M1 and M5, respectively, and 59-fold greater affinity for M3 compared to both M2 and M4). M3 receptors are involved in contraction of human bladder and gastrointestinal smooth muscle, saliva production, and iris sphincter function. Adverse drug effects such as dry mouth, constipation and abnormal vision may be mediated through effects on M3 receptors in these organs.

Before taking darifenacin, tell your doctor:

• If you are allergic to darifenacin; 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 have any of these health problems: Glaucoma, liver disease, slow clearing of the stomach, or trouble passing urine.

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

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 darifenacin 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 darifenacin?

• Tell all of your health care providers that you take darifenacin. This includes your doctors, nurses, pharmacists, and dentists.
• Avoid driving and doing other tasks or actions that call for you to be alert until you see how darifenacin affects you.
• Talk with your doctor before you drink alcohol or use other drugs and natural products that slow your actions.
• Be careful in hot weather or while being active. Drink lots of fluids to stop fluid loss.
• A very bad reaction called angioedema has happened with darifenacin. Sometimes, this may be life-threatening. Signs may include swelling of the hands, face, lips, eyes, tongue, or throat; trouble breathing; trouble swallowing; or unusual hoarseness. Get medical help right away if you have any of these signs.
• Tell your doctor if you are pregnant or plan on getting pregnant. You will need to talk about the benefits and risks of using darifenacin while you are pregnant.
• Tell your doctor if you are breast-feeding. You will need to talk about any risks to your baby.

How is darifenacin best taken?

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

• Take darifenacin at the same time of day.
• Take with or without food.
• Take with a full glass of water.
• Swallow whole. Do not chew, break, or crush.
• Keep taking darifenacin as you have been told by your doctor or other health care provider, even if you feel well.

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 darifenacin 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.
• Signs of a urinary tract infection (UTI) like blood in the urine, burning or pain when passing urine, feeling the need to pass urine often or right away, fever, lower stomach pain, or pelvic pain.
• Very bad headache.
• Feeling confused.
• Hallucinations (seeing or hearing things that are not there).
• Feeling sleepy.
• Very bad constipation.
• Very bad belly pain.
• Trouble passing urine.
• Change in eyesight.
• Not sweating during activities or in warm temperatures.
• Dizziness or passing out.
• Fever.
• Feeling tired or weak.
• Very upset stomach or throwing up.

What are some other side effects of darifenacin?

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:

• Heartburn.
• Constipation.
• Dry mouth.
• Upset stomach.
• Headache.

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 darifenacin?

• Store at room temperature.
• Protect from light.
• 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.

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