Oral drug dosing following bariatric surgery - General concepts and
specific dosing advices
Abstract
Bariatric or weight-loss surgery is a popular option for weight
reduction. Depending on the surgical procedure, gastric changes like
decreased transit time and volume and increased pH, decreased absorption
surface in the small intestine, decreased exposure to bile acids and
enterohepatic circulation, and decreased gastrointestinal transit time
may be expected. In the years after bariatric surgery, patients will
also substantially lose weight. As a result of these changes, the
absorption, distribution, metabolism, and/or elimination of drugs may be
altered. The purpose of this article is to report the general influence
of bariatric surgery on oral drug absorption, and to provide guidance
for dosing of commonly used or high-risk drugs in this special
population. Upon oral drug administration, the time to maximum
concentration is often earlier and this concentration may be higher with
less consistent effects on trough concentrations and exposure.
Additionally, prescription of liquid formulations to bariatric patients
is supported by some reports, even though the high sugar load of these
suspensions may be of concern. Studies on extended release medications
result in an unaltered exposure for a substantial number of drugs. Also,
studies evaluating the influence of timing after surgery show dynamic
absorption profiles. Although for this group a specific advice can be
proposed for many drugs, we conclude that there is insufficient evidence
for general advices for oral drug therapy after bariatric surgery
implying that a risk assessment on a case-by-case basis is required for
each drug.