Opiates/opioids are used predominantly for treating pain. The opiate codeine is also used as an antitussive (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 loperamide (sold as Imodium). Loperamide is used to treat diarrhea. However, loperamide does not cross into the brain, so it does not have abuse potential.
Centrally-acting opiates are Schedule II drugs, meaning they require a prescription and have abuse potential. Clinical uses for opiates include:
- diarrhea
- migraine
- moderate pain
- myalgia
- severe pain
- antitussives
Many newer analogs of morphine have been created that have vastly increased potency compared to morphine (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 on 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
- confusion
- constipation
- drowsiness
- euphoria
- hypotension
- nausea/vomiting
- physiological dependence/tolerance
- respiratory depression
- syncope
