If a sublingual tablet is swallowed, what happens to the concentration–time (CT) curve?

If a sublingual tablet is swallowed, what happens to the concentration–time (CT) curve?

• A. Shift down
• B. No change
• C. Shift up
• D. Shift right

Answer: (A)

Sublingual absorption gives rapid, high systemic levels because the drug enters circulation directly through the oral mucosa and largely bypasses first-pass metabolism. If the tablet is swallowed, it must dissolve in the GI tract and be absorbed there, with part of the dose degraded by the liver before reaching the bloodstream. This reduces the fraction that becomes available systemically, so plasma concentrations at any given time are lower than with proper sublingual administration. The overall concentration–time curve shifts downward to reflect the reduced Cmax and often reduced exposure (AUC). The onset may be slower, but the key effect described is a lower curve overall.

Sublingual absorption gives rapid, high systemic levels because the drug enters circulation directly through the oral mucosa and largely bypasses first-pass metabolism. If the tablet is swallowed, it must dissolve in the GI tract and be absorbed there, with part of the dose degraded by the liver before reaching the bloodstream. This reduces the fraction that becomes available systemically, so plasma concentrations at any given time are lower than with proper sublingual administration. The overall concentration–time curve shifts downward to reflect the reduced Cmax and often reduced exposure (AUC). The onset may be slower, but the key effect described is a lower curve overall.