Opiates/opioids are used predominantly for pain. However opiates such as codeine can be used as antitussives (to reduce coughing). A well-known effect of opiates is that they decrease GI motility. Opiate-induced constipation is a common side effect of opiates. This side effect is exploited in the drug loperimide (sold as Imodium). Loperimide is used to treat diarrhea. However loperimide does not cross into the brain so it does not have abuse potential.
Opiates are Schedule 2 drugs, meaning they require a prescription and have abuse potential. Clinical uses for opiates include:
- moderate pain
- severe pain
Many newer analogs of morphine have been created that have increased potency (such as sufentanil and fentanyl). Many opiates undergo metabolism to compounds that also have significant activity. For example, the drugs codeine and heroin, which have effects at opiate receptors, both get metabolized to morphine, which is also an active compound (see figure).
Opiates can cause:
- miosis (pinpoint pupils) and thus blurred vision
- physiological dependence / tolerance
- respiratory depression