Question

Due to an allergy to cats, a client has had several allergy attacks after visiting a family member. The physician has prescribed an antihistamine to reduce the symptoms. The client asks the nurse when would be the best time to take the antihistamine. The nurse's response is based on the knowledge that antihistamines A. transfer the allergic response to a mast cell. B. destroy the allergen that caused the symptoms C. block histamine from attaching to receptor sites. D. destroy histamine, the cause of allergic symptoms.

Short answer

The best time to take the antihistamine is before coming into contact with the allergen, as the medication works by blocking histamine from attaching to receptor sites, as described in option C.

Step-by-step solution

Understanding Antihistamines

Recognize that antihistamines are medications that block the histamine receptors on cells. Histamine is a chemical that can cause allergy symptoms when it binds to receptors on certain cells. Antihistamines prevent this binding and thus reduce or prevent the symptoms of an allergic reaction.

Eliminating Incorrect Options

Antihistamines do not transfer the allergic response to a mast cell; they cannot destroy allergens; nor do they destroy histamine itself. Instead, they work by preventing histamine from causing symptoms. Therefore, options A, B, and D can be eliminated.

Identifying the Correct Response

Select the option that correctly describes the function of antihistamines. In this scenario, choice C is accurate because it states that antihistamines block histamine from attaching to receptor sites, hindering its ability to trigger an allergic response.

Key concepts

Understanding Allergic Reactions

Allergic reactions are the body's hypersensitive responses to substances that are typically harmless to most people, known as allergens. Common allergens include pollen, pet dander, and certain foods. When a person with allergies encounters an allergen, their immune system mistakenly identifies it as a threat and releases chemicals like histamine into the bloodstream.

Histamine binds to receptors on certain cells, leading to symptoms such as sneezing, itching, runny nose, and watery eyes. Severe allergic reactions, known as anaphylaxis, can cause more extreme symptoms, including difficulty breathing, swelling, and a drop in blood pressure. Understanding these reactions is crucial for the effective management and treatment of allergies with antihistamines.

The Role of Histamine Receptor Blockers

Histamine receptor blockers, commonly known as antihistamines, play a critical role in managing allergic reactions. These medications work by blocking the action of histamine at the receptor sites on cells. As a result, they can prevent or alleviate the symptoms associated with allergic responses.

What's important to note is that antihistamines do not prevent the release of histamine from mast cells; they simply impede histamine from binding to its receptors, effectively 'blunting' the symptomatic effects. There are various types of antihistamines, and they may vary in effectiveness, duration of action, and side effects. Some antihistamines can cause drowsiness, which must be considered when planning medication administration timing.

Medication Administration Timing for Antihistamines

The timing for administering antihistamines is pivotal for maximizing their effectiveness while minimizing potential side effects. As a rule of thumb, antihistamines should be taken before exposure to known allergens when possible. This proactive approach allows the medication to bind to histamine receptors first, minimizing the likelihood and severity of an allergic reaction.

Some antihistamines are designed for once-daily dosing, while others may need to be taken more frequently. Patients should also be advised about the sedating effects of some antihistamines, especially first-generation drugs, which can affect activities such as driving or operating machinery. It's important to instruct patients to follow the prescribing physician's directions and to consider their daily routine and potential allergen exposure when taking their medication.