medications following bariatric surgery require adjustment
, according to a recently
published article in US Pharm
Bariatric surgery is performed in obese individuals
with BMI ≥40 kg/m2, or ≥35 kg/m2 with obesity-related health issues. Before
opting for surgery, these patients should have tried and failed other means of
weight loss. They should also be fit enough to undergo surgery. The patients
have to understand that treatment does not end with surgery but the
post-operative period will necessitate numerous follow-ups and additional
methods for weight loss.
surgeries include gastric restriction surgeries alone or combined with
procedures bringing about some type of malabsorption in the gastrointestinal
Gastric restriction surgeries include laparoscopic adjustable gastric banding,
vertical banded gastroplasty, and sleeve gastrectomy. In these surgeries, the
size of the stomach is reduced, thereby reducing its capacity. The patient is
thus able to eat only small portions of food at a time. In the laparoscopic
adjustable gastric banding procedure, an inflatable band is attached around the
stomach in such a way that the stomach is divided into an upper small pouch and
a lower larger pouch. The small pouch gets filled early, giving an early
feeling of satiety. In sleeve gastrectomy, most of the stomach is removed and
only a narrow tube-like structure is left behind. Vertical banded gastroplasty
involves stapling off a part of the stomach and using a band to create a narrow
opening to the rest of the stomach.
that use both gastric restriction and malabsorption include Roux-en-Y gastric
bypass and biliopancreatic diversion with duodenal switch. In Roux-en-Y gastric
bypass, a bypass is created such that the food does not pass through the entire
stomach and a part of the small intestine. In biliopancreatic diversion with
duodenal switch, sleeve gastrectomy is performed on the stomach and a diversion
for the food is created through the intestines.
procedures not only affect the absorption of food, they also alter the
absorption of various medications. Oral tablets are often broken down into finer
particles and dissolve in the stomach, thereby enabling absorption of the
medication in the digestive tract. A smaller stomach may interfere with the
disintegration and dissolution of the drug. Some drugs are more soluble in the
acidic pH of the stomach. These drugs will now spend shorter time in the
stomach and a longer duration in the alkaline intestines. This could affect the
disintegration, dissolution, and solubility of some medications. Oral liquid medications may be less
affected by bariatric surgery, since they do not have to disintegrate and
dissolve in the stomach. Sustained release and extended release tablets and
capsules should also be avoided since these formulations pass through the
digestive tract faster, and may get excreted without being absorbed.
Following weight reduction after bariatric surgery,
the dosage of some of the medications may require reduction. Processes that
could be affected following bariatric surgery include conversion of a prodrug
into its active form and the passage of some drugs through the liver, which is
required for their adequate action.
The effect of
oral contraceptives may be reduced following bariatric surgery. In addition, fertility may
be increased. Therefore, women in the reproductive age group following
bariatric surgery should be advised other methods of contraception like barrier
methods, intrauterine devices, vaginal rings, and injectable contraceptives.
supplementation to prevent anemia and vitamin C to create an acidic environment
to enhance the absorption of iron is recommended for these patients.
supplementation with calcium and vitamin D is advised in the patients
undergoing bariatric surgery to prevent deficiency and reduce the chances for
osteoporosis. Calcium citrate is best absorbed and should be recommended in
Other calcium supplements should be taken with food, to increase the acidity of
the stomach and thereby absorption.
Obese patients are often on psychiatric medications
for depression and other mood disorders. Changes in absorption of these medications
following bariatric surgery should be kept in mind, and dosages should be
adjusted accordingly. Some of these medications also increase weight; this has
to be kept in mind while prescribing these medications post-bariatric surgery.
Thus, use of
medications following bariatric surgery needs special consideration, often with
an adjustment of dosages. Additional aspects like contraception need to be
considered in women.
1. Bariatric Surgery in Women: Medication Considerations; Holly Anderson
et al; US Pharm. 2012;37(9):HS-12-HS-16.