Antitussives are useful in blocking the cough reflex and preserving the energy associated with prolonged, nonproductive coughing. Antitussives are best used with

A) STAT administration of atropine:
This is the correct answer. Atropine is a cholinergic antagonist that can increase heart rate by blocking the action of acetylcholine on cardiac muscarinic receptors. In cases of severe bradycardia, especially if associated with symptoms such as dizziness, syncope, or hypotension, atropine is often administered to increase heart rate and improve cardiac output. The dose of atropine and frequency of administration depend on the severity of bradycardia and the clinical response.

B) Administration of activated charcoal:
Activated charcoal is used in cases of overdose or poisoning to absorb ingested toxins and prevent their absorption into the bloodstream. However, in this scenario, where the primary concern is bradycardia resulting from cholinesterase inhibitor (donepezil) toxicity, activated charcoal would not be effective in reversing the bradycardic effects of the medication.

C) Hemodialysis:
Hemodialysis is a renal replacement therapy used to remove toxins and waste products from the blood in individuals with kidney failure. While hemodialysis may be indicated in cases of severe drug overdose or poisoning to enhance toxin elimination, it is not typically used as a first-line intervention for bradycardia associated with cholinesterase inhibitor toxicity.

D) Intravenous administration of pseudoephedrine:
Pseudoephedrine is a sympathomimetic drug that acts as a vasoconstrictor and can increase heart rate and blood pressure. While it may be used to treat bradycardia in some cases, such as severe symptomatic bradycardia unresponsive to atropine, it is not the first-line treatment for cholinesterase inhibitor toxicity-induced bradycardia. Atropine is preferred due to its direct antagonism of muscarinic receptors in the heart.

A) By blocking the effects of histamine in the body:
Antihistamines are pharmacological agents that work by antagonizing the effects of histamine, a chemical mediator released by mast cells and basophils in response to allergens or other triggers. Histamine contributes to various allergic symptoms such as itching, sneezing, nasal congestion, and watery eyes. Antihistamines exert their effects by competitively binding to histamine receptors (specifically H1 receptors) on target cells, thereby preventing histamine from binding and exerting its physiological effects. By blocking histamine receptors, antihistamines inhibit the action of histamine, leading to the alleviation of allergy symptoms.

B) By reducing inflammation in the body:
While some medications, such as corticosteroids, exert anti-inflammatory effects by suppressing the immune response and inhibiting the production of inflammatory mediators, antihistamines primarily target histamine receptors and do not directly reduce inflammation. Although histamine release can contribute to inflammation, antihistamines mitigate allergic symptoms primarily by blocking the action of histamine rather than by directly reducing inflammation.

C) By increasing the production of histamine in the body:
This statement is inaccurate. Antihistamines do not increase the production of histamine; instead, they counteract the effects of histamine by blocking its activity at receptor sites. The primary mechanism of action of antihistamines involves blocking histamine receptors to prevent histamine from exerting its physiological effects.

D) By stimulating the immune system:
Antihistamines do not stimulate the immune system. Instead, they act as antagonists to histamine receptors, thereby inhibiting histamine-induced responses. While histamine is involved in immune responses and allergic reactions, antihistamines do not directly modulate immune function or stimulate immune activity. Their primary role is to alleviate allergy symptoms by blocking the effects of histamine."