Which of the following antibiotics is associated with a risk of tendon rupture?

Choice A reason: Temporary swelling and rash are not common adverse effects of topical acyclovir. This antiviral inhibits viral DNA replication with minimal local irritation. Allergic reactions are rare, and swelling or rash would suggest hypersensitivity, not a typical response to topical application for genital herpes.

Choice B reason: Numbness and tingling are not associated with topical acyclovir. These symptoms may occur with systemic antivirals or nerve-related conditions, but topical acyclovir acts locally on herpes lesions with minimal systemic absorption, causing primarily mild irritation rather than neurological symptoms like paresthesia.

Choice C reason: Insomnia is not a side effect of topical acyclovir, which has negligible systemic absorption. Systemic antivirals like oral acyclovir may rarely cause CNS effects, but topical application is confined to the skin, primarily causing local irritation, not systemic effects like sleep disturbances.

Choice D reason: A burning sensation is a common adverse effect of topical acyclovir when applied to genital herpes lesions. The drug’s vehicle or local tissue irritation during application can cause transient burning or stinging, which is expected and typically resolves, requiring patient education to ensure adherence.

Choice A reason: Zileuton is a leukotriene synthesis inhibitor used in asthma management. It blocks 5-lipoxygenase, reducing leukotriene production, which mediates inflammation and bronchoconstriction. It has no anticholinergic effects, as it does not interact with muscarinic receptors or affect acetylcholine-mediated pathways, focusing solely on the arachidonic acid pathway for anti-inflammatory action.

Choice B reason: Aclidinium is a long-acting muscarinic antagonist (anticholinergic) used in COPD. It inhibits M3 muscarinic receptors in airway smooth muscle, reducing acetylcholine-induced bronchoconstriction and mucus secretion. This promotes bronchodilation, improving airflow. Its selective receptor binding ensures sustained airway relaxation, making it effective for maintenance therapy in obstructive lung diseases.

Choice C reason: Tiotropium, a long-acting anticholinergic, is used in COPD and sometimes asthma. It blocks M3 muscarinic receptors, preventing acetylcholine-mediated bronchoconstriction. This reduces airway resistance, enhances airflow, and decreases mucus production. Its prolonged action makes it suitable for daily maintenance, distinguishing it from non-anticholinergic drugs used in respiratory conditions.

Choice D reason: Budesonide is an inhaled corticosteroid that reduces airway inflammation by inhibiting inflammatory cytokine production. It does not have anticholinergic properties, as it does not affect muscarinic receptors or acetylcholine pathways. Its mechanism focuses on suppressing immune responses in the airways, making it effective for asthma and COPD management.

Choice E reason: Theophylline is a methylxanthine bronchodilator that relaxes airway smooth muscle by inhibiting phosphodiesterase, increasing cyclic AMP levels. It has no anticholinergic effects, as it does not block muscarinic receptors. Its mechanism is distinct, focusing on bronchodilation and anti-inflammatory effects, but it is less commonly used due to its narrow therapeutic index.