From the Research
Average Intrarectal Absorption Time for Liquids
- The average intrarectal absorption time for liquids is not explicitly stated in the provided studies, but we can look at the absorption times of specific drugs administered rectally to get an idea of the range.
- For diazepam solution, peak serum concentrations were achieved between 13-60 min, 10-120 min, and 30-90 min for 10 mg, 20 mg, and 30 mg doses, respectively 1.
- In another study, the median time to maximum concentration (Tmax) for diazepam rectal gel was 0.75 h, which is approximately 45 minutes 2.
- These studies suggest that the absorption time for liquids can vary depending on the drug and dosage, but it can range from around 10-120 minutes.
Factors Affecting Rectal Absorption
- The composition of the rectal formulation, such as the nature of the suppository base, can affect the absorption process 3, 4.
- The use of absorption-promoting agents, such as surfactants, can also influence rectal drug absorption 4.
- The site of drug administration in the rectum can affect the extent of first-pass metabolism, with the upper part of the rectum being connected to the portal system and the lower part being connected to the systemic circulation 3, 4.
Comparison of Rectal and Oral Absorption
- Rectal absorption can be lower than oral absorption due to the smaller surface area available for drug uptake 4.
- However, some studies have shown that rectal absorption can be comparable to or even exceed oral absorption for certain drugs, possibly due to partial avoidance of hepatic first-pass metabolism 3, 4.