Glossary · Pharmacology

Cmax

Definition: Cmax is the peak plasma concentration of a drug after dosing. Cmax matters for both efficacy and side effects — high Cmax can drive transient adverse effects, while low Cmax may indicate inadequate absorption. Sustained-release formulations smooth Cmax to provide steadier levels.

Detailed definition

Cmax is the maximum observed plasma concentration following a dose. For oral drugs, Cmax typically occurs 1–3 hours post-dose; for transdermal patches, 1–2 days post-application; for injectables, minutes to hours. High Cmax can correlate with side effects (e.g., high oral progesterone Cmax can produce pronounced sedation early after dosing). Sustained-release formulations smooth Cmax compared to immediate-release. Together with AUC, Cmax is one of the two parameters used in bioequivalence determinations.

Why it matters in menopause

For clinical purposes, Cmax shows up in discussions of side effect timing — for example, why bedtime oral progesterone is preferred (sedation peak coincides with desired sleep) and why some women feel sleepy 1–2 hours after morning patch change (transdermal Cmax effect is much smaller but real).

Sources

External references: Wikipedia.

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