Common adverse effects associated with the use of<unk>  include drowsiness and constipation. Less common are itching, nausea, vomiting, dry mouth, miosis, orthostatic hypotension, urinary retention, euphoria, and dysphoria. Rare adverse effects include anaphylaxis, seizure, acute pancreatitis, and respiratory depression. As with all opiates, long-term effects can vary, but can include diminished libido, apathy, and memory loss. Some people may have allergic reactions to<unk> , such as the swelling of skin and rashes. Tolerance to many of the effects of<unk> , including its therapeutic effects, develops with prolonged use. This occurs at different rates for different effects, with tolerance to the constipation-inducing effects developing particularly slowly for instance. A potentially serious adverse drug reaction, as with other opioids, is respiratory depression. This depression is dose-related and is a mechanism for the potentially fatal consequences of overdose. As<unk>  is metabolized to morphine, morphine can be passed through breast milk in potentially lethal amounts, fatally depressing the respiration of a breastfed baby. In August 2012, the United States Federal Drug Administration issued a warning about deaths in pediatric patients less than 6 years old after ingesting "normal" doses of paracetamol with<unk>  after tonsillectomy; this warning was upgraded to a black box warning in February 2013. Some patients are very effective converters of<unk>  to its active form, morphine, resulting in lethal blood levels. The FDA is presently recommending very cautious use of<unk>  in young tonsillectomy patients; the drug should be used in the lowest amount that can control the pain, "as needed" and not "around the clock", and immediate medical attention is needed if the user responds negatively. Withdrawal and dependence As with other opiates, chronic use of<unk>  can cause physical dependence which can lead to severe withdrawal symptoms if a person suddenly stops the medication. Withdrawal symptoms include drug craving, runny nose, yawning, sweating, insomnia, weakness, stomach cramps, nausea, vomiting, diarrhea, muscle spasms, chills, irritability, and pain. These side-effects also occur in acetaminophen/aspirin combinations, though to a lesser extent. To minimize withdrawal symptoms, long-term users should gradually reduce their<unk>  medication under the supervision of a healthcare professional. Also, no evidence indicates that CYP2D6 inhibition is useful in treating<unk>  dependence, though the metabolism of<unk>  to morphine (and hence further metabolism to glucuronide morphine conjugates) does have an effect on the abuse potential of<unk> . However, CYP2D6 has been implicated in the toxicity and death of neonates when<unk>  is administered to lactating mothers, particularly those with increased enzyme activity ("ultra-rapid" metabolizers).
Codeine
Morphine
Nalorphine
Ketazolam
Midazolam
Prilocaine
Benzocaine
Fentanyl