Clozapine Side Effects

Some of the more common side effects of clozapine include increased salivation, drowsiness, and weight gain. However, most people tolerate the drug without problems. If side effects do occur, they are typically minor and easily treated. Some clozapine side effects, however, should be reported to a healthcare provider right away, such as seizures, depression, and a rapid heart rate.

 

An Introduction to Clozapine Side Effects

As with any medicine, side effects are possible with clozapine (Clozaril®, FazaClo®). However, not everyone who takes the drug will experience side effects. In fact, most people tolerate it quite well. If side effects do occur, in most cases, they are minor and either require no treatment or are easily treated by you or your healthcare provider.
 
(This article covers many, but not all, of the possible side effects with clozapine. Your healthcare provider can discuss a more complete list of clozapine side effects with you.)
 

Common Clozapine Side Effects

Clozapine has been studied thoroughly in clinical trials. In these studies, the side effects that occur in a group of people taking the drug are documented and then compared to the side effects that occur in another group of people not taking the medicine. As a result, it is possible to see what side effects occur, how often they appear, and how they compare to the group not taking the medicine.
 
In these studies, the most common clozapine side effects included:
 
  • Increased salivation -- in up to 48 percent of people
  • Drowsiness -- up to 46 percent
  • Weight gain -- up to 31 percent (see Clozapine and Weight Gain)
  • Dizziness or vertigo (a spinning sensation) -- up to 27 percent
  • Constipation -- up to 25 percent
  • Insomnia -- up to 20 percent (see Clozapine and Insomnia)
  • Nausea -- up to 17 percent
  • Vomiting -- up to 17 percent
  • Indigestion or heartburn -- up to 14 percent.
     
Some other common side effects (occurring in 1 to 7 percent of people) included:
 
  • Headaches
  • Shakiness (tremors)
  • Increased sweating
  • Dry mouth (see Clozapine and Dry Mouth)
  • Nightmares
  • Restlessness
  • Agitation
  • Confusion
  • Fatigue or weakness
  • Slurred speech
  • Heartburn
  • Diarrhea
  • Loss of appetite
  • Problems with bladder control
  • Sexual problems (see Clozapine Sexual Side Effects)
  • Vision changes
  • Muscle weakness, spasms, or pain
  • A sore throat
  • Nasal congestion
  • A sore or numb tongue.
 
(Clozapine Side Effects Continued: Page 2)
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Written by/reviewed by: Kristi Monson, PharmD; Arthur Schoenstadt, MD
Last reviewed by: Kristi Monson, PharmD;