Why are renin inhibitors considered secondary line agents in hypertension treatment?

Renin inhibitors, such as aliskiren, are categorized as secondary line agents in the treatment of hypertension primarily due to their pharmacokinetic properties, particularly their low bioavailability. Low bioavailability indicates that a significant portion of the active compound is not absorbed into the systemic circulation when administered orally, which can result in variable and often insufficient therapeutic effects for managing hypertension. This limitation makes renin inhibitors less favorable as first-line agents compared to other antihypertensive medications, such as diuretics or ACE inhibitors, which have proven efficacy and better absorption profiles.

Moreover, while other factors may contribute to their positioning in treatment guidelines—such as cost considerations or safety profiles—bioavailability directly affects their efficacy and practical use in clinical settings. Hence, their use is typically reserved for cases where other treatments may not be adequate or appropriate, reaffirming their role as secondary line options.