Mental Health Home > Methadone Side Effects

Sedation, nausea, and dizziness are among the possible side effects reported with methadone. Although many side effects tend to be mild and generally do not require medical attention, you should contact your healthcare provider right away if you experience serious reactions to the medication, such as seizures, difficulty passing urine, or breathing problems.

An Introduction to Methadone Side Effects

Just like any medicine, methadone (Diskets®, Dolophine®, Methadose®) can cause side effects. However, not everyone who takes the medication will have problems. In fact, some people tolerate it quite well. If side effects do occur, in many 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 methadone. Your healthcare provider can discuss a more complete list of methadone side effects with you.)

Possible Side Effects of Methadone

For many medications, the prescribing information carefully explains the exact percentage of side effects that were seen in clinical trials. However, the prescribing information for almost all older medications, including many methadone products, includes only vague information about side effects, with no percentages provided.
Therefore, it can be difficult to know exactly how common or how rare the side effects of such medications may be.
The most common side effects of methadone are thought to include:
  • Nausea
  • Vomiting
  • Lightheadedness
  • Dizziness
  • Sedation
  • Sweating.
Other possible bothersome (but not usually serious) side effects that have been reported include but are not limited to:
  • Weakness
  • Headaches
  • Flushing
  • Loss of appetite
  • Abdominal pain (stomach pain)
  • Constipation
  • Dry mouth
  • Flushing of the skin
  • Weight gain
  • Insomnia
  • Decreased sex drive.
In general, side effects usually become less noticeable after the first several weeks of use, although sweating and constipation often persist.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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