Bipolar Disorder Home > Olanzapine Side Effects
Olanzapine 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 are then compared to side effects that occur in another group of people not taking the medicine. This way, 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 olanzapine side effects included:
- Drowsiness -- in up to 48 percent of people
- Dry mouth -- up to 32 percent (see Zyprexa and Dry Mouth)
- Weight gain -- up to 26 percent (see Zyprexa and Weight Gain)
- Increased appetite -- up to 29 percent
- Dizziness -- up to 18 percent
- Weakness -- up to 18 percent
- Headache -- up to 17 percent
- Fatigue -- up to 14 percent
- Accidental injury -- up to 12 percent
- Insomnia -- up to 12 percent (see Zyprexa and Insomnia)
- Constipation -- up to 11 percent
- Heartburn or indigestion -- up to 11 percent
- Thirst -- up to 10 percent.
Some other common side effects of olanzapine (occurring in 5 percent to 9 percent of people) included:
- Personality changes
- Shakiness (tremors)
- Low blood pressure, especially when sitting or standing up
- A fever
- Back pain
- Joint pain
- Changes in walking pattern
- An irritated or runny nose
- Speech problems
- Increased salivation
- Memory loss (amnesia).
The side effects and percentages listed above were taken from clinical trials involving Zyprexa tablets, orally disintegrating tablets (Zyprexa Zydis®), or the short-acting injection form. A newer, long-acting injection form (Zyprexa Relprevv™) is also available. This form has similar side effects as the others, with one notable exception -- Zyprexa Relprevv sometimes causes a serious side effect known as post-injection delirium/sedation syndrome (in about 2 percent of people), as discussed.