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Grass Pollen Allergen Extract (Timothy Grass)


(GRAS POL uhn al er juhn EK strakt TIM oh thee GRAS)

Index Terms

  • Timothy Grass

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Tablet Sublingual, Sublingual:

Grastek: 2800 bau [contains gelatin (fish)]

Brand Names: U.S.

  • Grastek

Pharmacologic Category

  • Allergen-Specific Immunotherapy


Grass pollen allergen extract contains extract from timothy grass. While the exact mechanism has not been fully elucidated, specific immunotherapy (SIT) may act by inducing a switch from T helper 2 cell response (Th2) to T helper 1 cell (Th1) response resulting in decreased interleukin-4 (IL-4) and interleukin-5 (IL-5) and increased interleukin-10 (IL-10), production of IgG-blocking antibodies that compete with IgE antibodies for allergen binding, proliferation of regulatory T lymphocytes and cytokines, and decreases in mast cells, eosinophils, and early- and late-phase allergic responses (Leith 2006).

Use: Labeled Indications

Grass pollen-induced allergic rhinitis: Immunotherapy for the treatment of grass pollen-induced allergic rhinitis with or without conjunctivitis confirmed by positive skin test or in vitro testing for pollen-specific IgE antibodies for timothy grass or cross-reactive grass pollens in patients 5 through 65 years of age. Not indicated for the immediate relief of allergy symptoms.


Hypersensitivity to any of the inactive ingredients (gelatin, mannitol, and sodium hydroxide) contained in this product or any other component of the formulation; severe, unstable or uncontrolled asthma; history of any severe systemic allergic reaction; history of any severe local reaction to sublingual allergen immunotherapy; history of eosinophilic esophagitis

Canadian labeling: Additional contraindications (not in US labeling): Unstable, severe chronic, or severe seasonal asthma (FEV1 <70% of predicted value in adults; <80% in children); concomitant beta-blocker therapy; oral inflammation (eg, oral lichen planus, oral ulcerations, severe oral candidiasis, or dental extraction)

Dosing: Adult

Dosage strength expressed in Bioequivalent Allergy Units (BAU). Note: Initiate treatment ≥12 weeks before expected onset of each pollen season and continue throughout pollen season. May be taken daily for 3 consecutive years (including intervals between grass pollen seasons). Safety and efficacy of initiating treatment during grass pollen season or restarting treatment after missing a dose have not been established. In clinical trials, treatment interruptions ≤7 days were allowed.

Grass pollen-induced allergic rhinitis: Adults ≤65 years: Sublingual: One tablet (2,800 BAU) once daily

Dosing: Pediatric

Dosage strength expressed in Bioequivalent Allergy Units (BAU).

Grass pollen-induced allergic rhinitis: Children ≥5 years and Adolescents: Refer to adult dosing.

Dosing: Renal Impairment

There are no dosage adjustments provided in the manufacturer’s labeling.

Dosing: Hepatic Impairment

There are no dosage adjustments provided in the manufacturer’s labeling.


Sublingual: Administer first dose in a healthcare setting due to the potential for allergic reactions; monitor patient for 30 minutes after first dose. If well tolerated, subsequent doses may be taken at home; subsequent pediatric doses should be done under adult supervision. Remove sublingual tablet from blister unit with dry hands immediately prior to administration. Place tablet under tongue until completely dissolved (≥1 minute) and then swallow. Wash hands after handling tablet. Avoid food or beverage for 5 minutes following dissolution of tablet (to prevent the swallowing of allergen extract). Auto-injectable epinephrine should be made available to patients.


Store between 20°C and 25°C (68°F and 77°F); excursions are permitted between 15°C and 30°C (59°F and 86°F). Protect from moisture.

Drug Interactions

There are no known significant interactions.

Adverse Reactions


Dermatologic: Pruritus of ear (7% to 13%)

Gastrointestinal: Oral itching (24% to 27%)

Hypersensitivity: Mouth edema (10% to 11%)

Respiratory: Throat irritation (21% to 23%)

1% to 10%:

Cardiovascular: Chest discomfort (2%), lip edema (adults: 1%)

Central nervous system: Headache (2% to 3%), oral hypoesthesia (1% to 2%), fatigue (adults: 1%)

Dermatologic: Tongue pruritus (6% to 9%), lip pruritus (children and adolescents: 3%), pruritus (adults: 2%), urticaria (2%)

Endocrine & metabolic: Palatal edema (adults: 1%)

Gastrointestinal: Oral paresthesia (5% to 10%), lip swelling (4% to 7%), oral mucosa erythema (2% to 5%), swollen tongue (3%), dyspepsia (adults: 2%), nausea (2%), oral discomfort (2%), dysphagia (1% to 2%), glossalgia (1%), glossitis (adults: 1%), stomatitis (1%), tongue disease (adults: 1%), abdominal pain (adults: ≤1%), gastroesophageal reflux disease (adults: ≤1%)

Ophthalmic: Eye pruritus (children and adolescents: 3%)

Respiratory: Pharyngeal erythema (children and adolescents: 4%), oropharyngeal pain (2% to 4%), cough (children and adolescents: 3%), pharyngeal edema (3%), dry throat (adults: 2%), nasal congestion (children and adolescents: 2%), nasal discomfort (2%), sneezing (children and adolescents: 2%), dyspnea (1% to 2%), constriction of the pharynx (adults: 1%)

Postmarketing and/or case reports: Anaphylactic shock, anaphylaxis, angioedema, cardiac rate disturbance, chest pressure, decrease in forced vital capacity, diarrhea, dizziness, drowsiness, dysarthria, eosinophilic esophagitis, exacerbation of asthma, exacerbation of ulcerative colitis, exercise-induced asthma, facial edema, facial erythema, foreign body sensation, hoarseness, hypersensitivity reaction, hyperventilation, hypotension, impaired consciousness, increased heart rate, laryngeal discomfort, laryngitis, local hypersensitivity reaction, neck edema, oral mucosa ulcer, oxygen saturation decreased, peak expiratory flow rate decreased, localized swelling (enlarged uvula), pneumonia, reduced forced expiratory volume, respiratory distress, skin rash, status asthmaticus, stridor, tremor, vomiting, wheezing

ALERT: U.S. Boxed Warning

Severe allergic reactions:

Grass pollen allergen extract can cause life-threatening allergic reactions such as anaphylaxis and severe laryngopharyngeal restriction. Do not administer to patients with severe, unstable, or uncontrolled asthma. Observe patients in the office for at least 30 minutes following the initial dose. Prescribe auto-injectable epinephrine, instruct and train patients on its appropriate use, and instruct patients to seek immediate medical care upon its use. Grass pollen allergen extract may not be suitable for patients with certain underlying medical conditions that may reduce their ability to survive a serious allergic reaction. Grass pollen allergen extract may not be suitable for patients who may be unresponsive to epinephrine or inhaled bronchodilators, such as those taking beta-blockers.


Concerns related to adverse effects:

• Esophagitis: Eosinophilic esophagitis has been reported with sublingual tablet immunotherapy; discontinue therapy in patients who experience severe or persistent gastroesophageal symptoms (eg, dysphagia, chest pain). Use is contraindicated in patients with a history of eosinophilic esophagitis.

• Hypersensitivity reactions [US Boxed Warning]: Severe, life-threatening allergic reactions, including anaphylaxis and severe laryngopharyngeal restrictions, may occur. Local reactions in the mouth or throat may occur; consider discontinuation in patients experiencing escalating and persistent adverse reactions in the mouth or throat. Increased risk of local or systemic adverse reactions may occur when given with concomitant allergen immunotherapy.

Disease-related concerns:

• Respiratory disease: [US Boxed Warning]: Do not administer to patients with severe, unstable, or uncontrolled asthma; use has not been studied in patients with moderate or severe asthma or in patients requiring daily medication. Withhold treatment if patient is experiencing an acute asthma exacerbation. Re-evaluate patients with recurrent asthma exacerbations and consider discontinuation.

Concurrent drug therapy issues:

• Vaccines: Effect of vaccination during therapy has not been evaluated.

Other warnings/precautions:

• Administration: [US Boxed Warning]: Auto-injectable epinephrine should be prescribed to patients; instruct patients on appropriate use and to obtain immediate medical care upon its use.

• Appropriate patient selection: [US Boxed Warning]: Use may not be suitable for patients with conditions that may reduce their ability to survive a serious allergic reaction, including but not limited to compromised lung function (either chronic or acute) and cardiovascular conditions (eg, unstable angina, recent MI, arrhythmia, and uncontrolled hypertension).

• Appropriate use: [US Boxed Warning]: Use may not be suitable for patients who may be unresponsive to epinephrine or inhaled bronchodilators due to concomitant drug therapy. The effect of epinephrine may be potentiated or inhibited by the following medications: beta blockers, alpha blockers, ergot alkaloids, tricyclic antidepressants, levothyroxine, monoamine oxidase inhibitors, antihistamines, cardiac glycosides, and diuretics.

• Monitoring: [US Boxed Warning]: Monitor all patients for at least 30 minutes after initial dose in a health care setting under the supervision of a physician with experience in the diagnosis and treatment of allergic diseases. Each subsequent dose in pediatric patients should be done under direct adult supervision.

• Oral inflammation/wounds: Discontinue therapy to allow for complete healing of the oral cavity due to oral inflammation (eg, oral lichen planus, mouth ulcers, or thrush) or oral wounds following oral surgery or dental extraction.

Monitoring Parameters

Signs/symptoms of hypersensitivity; monitor patients for at least 30 minutes after administration of first dose.

Pregnancy Risk Factor


Pregnancy Considerations

Adverse events have not been observed in animal reproduction studies.

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience itching in the ear, mouth, or tongue or numbness or tingling of the mouth. Have patient report immediately to prescriber difficulty swallowing, painful swallowing, difficulty speaking, heartburn, angina, tachycardia, passing out, dizziness, flushing, shortness of breath, high-pitched abnormal breathing sound, persistent cough, severe diarrhea, severe nausea, vomiting, abdominal cramps, severe abdominal pain, severe mouth irritation, thrush, or severe pharyngitis (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.