Maintaining steady state drug levels depends primarily on the timing of drug administration to balance drug input and elimination. A consistent dosing interval ensures that the drug concentration remains within the therapeutic window, preventing peaks and troughs that can lead to toxicity or subtherapeutic effects. Variations in timing disrupt this balance, causing fluctuations in plasma levels. While factors like patient weight or route of administration influence dosing, they do not directly control steady state maintenance as reliably as dosing intervals do. Therefore, consistent dosing intervals are critical for stable drug levels.

Reference: Goodman & Gilman’s: The Pharmacological Basis of Therapeutics, Brunton et al., 13th Edition.