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Chapter 29: Psychopharmacological Treatment
be swallowed whole, never crushed, chewed, or cut. The maxi-
mum daily dose is 75 mg.
Side effects include dry mouth, unpleasant taste, restlessness,
anxiety, dizziness, depression, tremors, upset stomach, vomit-
ing, and increased urination. Side effects that warrant medical
attention include tachycardia, palpitations, blurred vision, skin
rash, itching, difficulty breathing, chest pain, fainting, swelling
of the ankles or feet, fever, sore throat, chills, and painful uri-
nation. Diethylpropion is classified pregnancy Category B and
has a low abuse potential. It is listed as a Schedule IV drug by
the DEA.
Orlistat (Xenical, Alli)
Orlistat interferes with the absorption of dietary fats, caus-
ing reduced caloric intake. It works by inhibiting gastric and
pancreatic lipases, the enzymes that break down triglycerides
in the intestine. When lipase activity is blocked, triglycerides
from the diet are not hydrolyzed into absorbable free fatty acids
and are excreted undigested instead. Only trace amounts of orl-
istat are absorbed systemically; it is almost entirely eliminated
through the feces.
The effectiveness of orlistat in promoting weight loss is defi-
nite, though modest. When used as part of weight loss program,
between 30 and 50 percent of patients can expect a 5 percent or
greater decrease in body mass. About 20 percent achieve at least
a 10 percent decrease in body mass. After orlistat is stopped, up
to a third of people gain the weight they lose.
Among the benefits of orlistat treatment are a decrease in
blood pressure and a reduced risk of developing type 2 diabetes.
The most common subjective side effects of orlistat are
gastrointestinal related, and include steatorrhea, flatulence,
fecal incontinence, and frequent or urgent bowel movements.
To minimize these effects, foods with high fat content should
be avoided; a low-fat, reduced calorie diet is advisable. Ironi-
cally, orlistat can be used with high-fat content diets to treat
constipation that results from treatment with some psychotropic
drugs, such as the tricyclic antidepressants. Side effects are most
severe when beginning therapy and may decrease in frequency
with time. Hepatic and renal injuries are potentially serious side
effects of orlistat use. In 2010, new safety information about
rare cases of severe liver injury was added to the product label
of orlistat. The rate of acute kidney injury is more common
among orlistat users than nonusers. It should be used with cau-
tion in patients with impaired liver function and renal function,
as well as those with an obstructed bile duct and pancreatic dis-
ease. Orlistat is contraindicated in malabsorption syndromes,
hypersensitivity to orlistat, reduced gallbladder function, and
in pregnancy and breast-feeding. Orlistat is rated pregnancy
Category X.
Absorption of fat-soluble vitamins and other fat-soluble
nutrients is inhibited by the use of orlistat. Multivitamin supple-
ments that contain vitamins A, D, E, K, as well as
b
-carotene
should be taken once a day, preferably at bedtime.
Orlistat can reduce plasma levels of the immunosuppressant
cyclosporine (Sandimmune), so the two drugs should therefore
not be administered concomitantly. Orlistat can also impair
absorption of the antiarrhythmic amiodarone (Nexterone).
At the standard prescription dose of 120 mg three times
daily before meals, orlistat prevents approximately 30 percent
of dietary fat from being absorbed. Higher doses have not been
shown to produce more pronounced effects.
An over-the-counter formulation of orlistat (Alli) is available
as 60-mg capsules—half the dosage of prescription orlistat.
Lorcaserin (Belviq)
This drug is awaiting approval by the FDA because it appears to
have hallucinogenic potential. The exact mechanism of action
of lorcaserin is not known, but it most likely decreases food
consumption and promotes satiety through selective activation
of 5-HT
2C
receptors on neurons in the hypothalamus.
The effect of multiple oral doses of lorcaserin 15 mg and
40 mg once daily on QTc interval has been evaluated in healthy
subjects. The largest placebo adjusted, baseline-corrected QTc
based on individual correction method (QTcI) was below
10 milliseconds, the threshold for regulatory concern.
Lorcaserin is absorbed from the gastrointestinal tract, with
peak plasma concentration occurring 1.5 to 2 hours after oral
dosing. The absolute bioavailability of lorcaserin has not been
determined. Lorcaserin has a plasma half-life of approximately
11 hours; steady state is reached within 3 days after twice daily
dosing, and accumulation is estimated to be approximately 70
percent. Lorcaserin can be administered with or without food.
Lorcaserin hydrochloride is moderately bound (approximately
70 percent) to human plasma proteins.
It is extensively metabolized in the liver by multiple enzy-
matic pathways, and the metabolites are excreted in the urine.
Lorcaserin and its metabolites are not cleared by hemodialysis.
It is not recommended for patients with severe renal impairment
(creatinine clearance less than 30 mL per minute) or patients
with end-stage renal disease.
The half-life of lorcaserin is prolonged by 59 percent to
19 hours in patients with moderate hepatic impairment. Lorca-
serin exposure (area under the curve) is approximately 22 and
30 percent higher in patients with mild and moderate hepatic
impairment, respectively. Dose adjustment is not required for
patients with mild to moderate hepatic impairment.
No dosage adjustment based on gender is necessary because
it did not meaningfully affect the pharmacokinetics of lorcase-
rin. No dosage adjustment is required based on age alone.
Lorcaserin significantly inhibits CYP2D6-mediated
metabolism.
Drugs Without U.S. Food and Drug
Administration Approval for
Weight Loss
Topiramate
Topiramate and zonisamide (Zonegran) are discussed more fully
in Section 29.6, but are mentioned here because both agents can
have a substantial effect on weight loss.
Topiramate is approved as an antiepileptic drug and for pre-
vention in adults of migraine headaches. The degree of weight
loss associated with topiramate may be comparable to the weight
loss that other FDA-approved antiobesity drugs induce. Small
studies and extensive anecdotal reports indicate that topiramate
can help to offset weight gain associated with selective serotonin
reuptake inhibitors (SSRIs) and second-generation antipsychotic
