Respiratory stimulants: Nursing pharmacology

Respiratory stimulants are a group of medications that can be administered to clients with asthma, chronic obstructive pulmonary disease or COPD for short, or respiratory depression; as well as to treat apnea of prematurity.

Respiratory stimulants include doxapram, which is administered intravenously, as well as certain phosphodiesterase enzyme inhibitors, also known as methylxanthines, such as caffeine, theophylline, and aminophylline, which are most often taken orally, but they can also be given intravenously.

Once administered, these medications primarily work on the brainstem and medulla by stimulating the respiratory center, and thus act as respiratory stimulants.

In addition, methylxanthines can also act on the lungs by inhibiting the phosphodiesterase enzyme, and ultimately cause bronchodilation.

Side effects commonly caused by respiratory stimulants include muscle tremors, agitation, anxiety, irritability, and insomnia. Clients might also experience gastrointestinal disturbances like nausea, vomiting, and diarrhea.

These drugs may also cause hypertension, heart palpitations, tachycardia, and ECG abnormalities.

In addition, theophylline has a very narrow therapeutic window, meaning it's very easy to overdose, and can cause arrhythmias or seizures.

Finally, administering high doses of caffeine to premature infants can lead to intracranial hemorrhage.

As far as contraindications go, respiratory stimulants are contraindicated in clients with severe arteriosclerosis, symptomatic cardiovascular disease, and moderate to severe hypertension.

Respiratory stimulants should also be avoided in clients with a history of seizures, as well as hepatic or renal disease.

Additional precautions should be taken during pregnancy and breastfeeding. Regarding interactions, theophylline and phenytoin should not be used together, as they decrease each other’s effects.

Finally, theophylline should not be combined with beta blockers, beta adrenergic agonists, antidepressants, H2 blockers like cimetidine, or certain antibiotics like ciprofloxacin, as well as tobacco smoke and marijuana, since these medications can increase the levels of theophylline and result in toxicity. Due to the dangerous potential side effects, theophylline is now rarely used.

Now, when caring for a client who is prescribed a respiratory stimulant like theophylline to improve their respiratory function, first perform a baseline assessment, including vital signs, especially respiratory rate, as well as SpO2, and lung sounds. Then, review your client’s recent laboratory test results, including renal and hepatic function.