Final answer:
An overdose of decongestants in older adults typically leads to increased blood pressure or hypertension (HTN), prominently due to the alpha-1 adrenergic agonist action of common decongestant constituents such as phenylephrine.
Step-by-step explanation:
Overdosing on decongestants can lead to various adverse effects. Common decongestants such as phenylephrine and pseudoephedrine can lead to an increase in blood pressure due to their sympathomimetic effects. In older adults, an overdose of decongestants may cause symptoms like headache, stiff neck, loss of balance, and convulsions, in addition to increased blood pressure or hypertension (HTN). These adverse effects are related to the drugs' actions on alpha-1 adrenergic receptors, which can lead to constriction and tightening of blood vessels and an increase in blood pressure. Hallucinations are more commonly linked to other substances and are not a typical result of decongestant overdose.