Ipratropium bromide

Ipratropium bromide is a medication that opens the middle and large airways in the lungs. It is used to treat the symptoms of chronic obstructive pulmonary disease and asthma. It is a quaternary ammonium derivative of atropine, which belongs to the group of anticholinergics. It is usually administered by inhalation, which provides a local effect without significant systemic side effects.

Pharmacodynamics

Ipratropium, due to its structural relationship to the neurotransmitter acetylcholine, acts as an antagonist of the muscarinic acetylcholine receptor. This effect causes the inhibition of the parasympathetic nervous system in the respiratory tract, thus inhibiting its function. The function of the parasympathetic nervous system in the airways is to produce bronchial secretions and constriction, and therefore inhibition of this effect can lead to bronchodilation and decreased secretions. As a result, breathing is facilitated.

Pharmacokinetics

Protein binding of ipratropium is very low as the level of circulating ipratropium is minimal. The bound state accounts for only 0-9% of the administered dose. Ipratropium is metabolized in the gastrointestinal tract by the activity of cytochrome P-450 isozymes. Approximately 80-100% of the administered dose of ipratropium is excreted in the urine, with less than 20% of the dose eliminated in the feces. Ipratropium has a short half-life of approximately 1.6 hours.

Drug Interactions

Interactions with other anticholinergics such as tricyclic antidepressants, anti-Parkinsonian agents, and quinidine, which theoretically potentiate side effects, are clinically irrelevant when ipratropium is administered as an inhalant because the systemic blood plasma concentration of ipratropime is very low.

Side effects

Common side effects include dry mouth, cough, and inflammation of the respiratory tract. Potentially serious side effects include urinary retention, worsening respiratory spasms, and a severe allergic reaction. Use during pregnancy and lactation is generally considered safe.

Toxicological Data

LD50 (rat, oral): 1663 mg-kg-1