Whether allergy medicine can be taken on an empty stomach depends on the specific drug and its formulation. Allergy medicines primarily consist of antihistamines, which block the effects of histamine, and sometimes include decongestants. For most common, modern formulas, taking the medication without food is acceptable. However, an empty stomach can sometimes alter the drug’s speed or lead to discomfort.
The Impact of Food on Drug Absorption
Taking most modern, second-generation antihistamines on an empty stomach does not compromise their overall effectiveness. The total amount of drug that enters the bloodstream (bioavailability) often remains unchanged whether taken with or without a meal, such as with cetirizine. However, food can influence the rate at which the drug begins to work. Consuming a meal can delay the time it takes for cetirizine and levocetirizine to reach maximum concentration in the blood by about 1.7 hours, meaning symptom relief may be slightly slower. This delay and a slight reduction in peak concentration are generally not considered clinically significant, as the drug remains effective over its 24-hour dosing period. Loratadine’s effectiveness is also not significantly altered by food intake.
Gastrointestinal Distress and Safety Concerns
Taking medication on an empty stomach can introduce the risk of gastrointestinal irritation, even with generally well-tolerated modern antihistamines. The lack of a buffer exposes the sensitive stomach lining to the medication, potentially leading to discomfort. This concern is more pronounced with older, first-generation antihistamines or formulations that include decongestants like pseudoephedrine. Taking these specific medications with food helps coat the stomach lining and dilutes the drug concentration, minimizing irritation. If a person experiences heartburn, nausea, or stomach pain, they should ingest the medicine alongside a light meal.
Specific Medications Requiring or Prohibiting Food
Medications That Must Be Taken Away from Food
A few specific allergy medications are exceptions to the general rule and have strict instructions regarding food and drink consumption. Fexofenadine (Allegra) is one drug where food interactions can severely reduce its efficacy. Taking fexofenadine with certain fruit juices, including grapefruit, apple, and orange, can decrease drug absorption by up to 70%.
This occurs because the juices inhibit transporters responsible for moving the drug from the intestine into the bloodstream. Therefore, fexofenadine should only be taken with water, and these juices should be avoided for at least two to four hours before and after dosing. High-fat meals also decrease fexofenadine’s absorption, supporting the need to take this drug on an empty stomach for maximum effectiveness.
Medications Recommended with Food
The most common reason a medication label recommends taking a drug with food is to prevent or minimize stomach irritation. Certain decongestants often included in combination allergy and cold medicines are known to be slightly harsher on the gastric lining. Following the label instruction to take these formulations with a meal is advisable to ensure comfort.