Budesonide
Budesonide. Glucocorticoid — used inhaled for asthma maintenance, intranasally for allergic rhinitis, and orally as a delayed-release (Entocort)… Oral half-life 2.8 h.
Glucocorticoid — used inhaled for asthma maintenance, intranasally for allergic rhinitis, and orally as a delayed-release (Entocort) for ileal Crohn's with high first-pass metabolism reducing systemic effect.
PK: THERE IS NO SUCH THING AS "THE INHALED BIOAVAILABILITY" OF THIS DRUG. Systemic availability spans 15% to 39% and lung deposition 14% to 32% PURELY BY DEVICE — and plasma does not even order the systemic effect, since one device delivers more drug to plasma yet suppresses cortisol less. The inhaled and intranasal routes therefore carry no plasma block and should be keyed to device if they ever acquire one. The half-life IS legitimately route-independent, measured after inhalation, oral AND intravenous dosing in the same volunteers, so that structural practice was right; only the number and its sourcing were wrong, and 2.8 h now replaces an unsourced 3 h. V 200 L is replaced by the only human intravenous measurement, 301 L, and F by the plain-oral 10.7% from the same study rather than the 11% adult subgroup of six Crohn patients on a controlled-release capsule. ka 1 is dropped and is structurally wrong for the formulation the record cited: controlled ileal release shifts time to peak from 1.8 to 4.5 hours with over 60% absorbed from ileum and colon. A reference is a medicinal-chemistry paper that never mentions budesonide.
Pharmacokinetics
- Oral — t½ 2.8 h · F 11% · Vd 301 L
- Inhaled — t½ 2.8 h · F 39% · Vd 210 L
Sources: PMID:12492736, PMID:6958498, PMID:11736861, PMID:12468958