Medication Search​ - Grastek

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Common Name:

Timothy grass allergenic extract


How does Grastek work? What will it do for me?

Timothy grass allergenic extract belongs to the class of medications called allergy immunotherapies. It is used to decrease the symptoms of moderate to severe seasonal allergies to Timothy grass and related grass pollens, when other allergy treatments have not been effective. Before treatment with Timothy grass allergenic extract, your doctor will confirm your allergy with either a skin or a blood test.

This medication works by causing the body’s immune system to become less sensitive to the effects of the pollen. It may be started at any point during the year however, for symptoms to improve during the first allergy season, it should be started 8 to 12 weeks before the grass pollen season begins.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does Grastek come in?

Each white to off-white circular sublingual tablet with a debossed, round detail on one side contains 2800 BAU (Bioequivalent Allergen Units) of standardized natural grass pollen extract of Timothy Grass (Phleum pretense). Nonmedicinal ingredients: gelatin NF (fish source) mannitol USP and sodium hydroxide NF.

How should I use Grastek?

The recommended dose for adults and children 5 years of age and older is 1 sublingual tablet containing 2800 Bioequivalent Allergy Units (BAU), dissolved under the tongue once daily.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

To use this medication, with dry hands, remove the tablet from the foil packaging immediately before you use it. Place the tablet under your tongue and allow it to dissolve. Avoid swallowing for 1 minute to allow the medication to be absorbed through the skin in your mouth. Avoid eating or drinking anything for 5 minutes after taking the tablet and wash your hands after handling the medication.

It is important that this medication be taken exactly as prescribed by your doctor.

If you miss a dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children. Keep this medication in its original package until you are ready to use a dose.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take Grastek?

Do not take Timothy grass allergenic extract if you:

  • are allergic to any non-medicinal ingredients of the medication
  • have previously had a severe allergic reaction to Timothy or related grass immunotherapy
  • have severe chronic or seasonal asthma
  • are taking a medication in the β-blocker family
  • have sores, yeast infection or other inflammation in the mouth

Do not give this medication to children less than 5 years of age.

What side effects are possible with Grastek?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • allergy symptoms (e.g., runny nose, stuffy nose, itchy watery eyes)
  • asthma symptoms (e.g., wheezing, difficulty breathing, cough)
  • cough
  • dizziness
  • dry mouth
  • ear or eye itchiness
  • headache
  • hives or itching all over body
  • mouth tingling, itching or swelling
  • swollen tongue
  • throat irritation
  • tiredness

Although most of the side effects listed below don’t happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • bleeding gums
  • blocked feeling in the ear
  • chest discomfort
  • enlarged glands
  • nose bleeds
  • stomach pain

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • change of voice
  • signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
  • throat tightness
  • trouble breathing
  • trouble swallowing

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for Grastek?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Allergic Reactions: Some people who take this medication experience a severe allergic reactions. Before you take Timothy grass allergenic extract, inform your doctor about any previous adverse reactions you have had to medications, especially medications used to treat grass allergies. Contact your doctor at once if you experience signs of an allergic reaction, such as skin rash, itching, difficulty breathing or swelling of the face and throat.

Milder allergic reactions such as hives, itching, mouth itchiness, runny nose and throat irritation can occur with the use of this medication. If these side effects become bothersome, discuss your concerns with your doctor.

Asthma: This medication may cause asthma symptoms or cause existing asthma symptoms to worsen. If you have a history of asthma, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. People with uncontrolled asthma should not use this medication.

First dose: Severe allergic reactions have occurred with the first dose of this medication. For this reason, the first dose should be taken at your doctor’s office or a similar location where emergency treatment is available if the medication causes a severe reaction. Your doctor will likely want you to remain in the office for at least 30 minutes after taking the dose, to ensure that it does not cause a severe allergic reaction.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if Timothy grass allergenic extract passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children under 5 years of age. Children should be supervised for at least 30 minutes after taking each dose of this medication.

What other drugs could interact with Grastek?

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

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