Answer to Question 1
Morphine: reduces wakefulness and alertness; is an agonist at enkephalin receptors; can induce very uncomfortable withdrawal following chronic use; induces effects blocked by opiate antagonists; has potent analgesic properties; induces respiratory depression; induces constipation; constricts pupils. Cocaine: enhances wakefulness and alertness; blocks dopamine reuptake; induces no severe withdrawal following chronic use; effects not blocked by opiate antagonists; has little or no analgesic qualitiesalthough it can act as a local anesthetic; induces no respiratory depression or constipation; dilates pupils.
Answer to Question 2
Methadone and naltrexone are both orally effective and long-lasting drugs that reduce (methadone) or eliminate (naltrexone) the reinforcing effects that might accompany heroin administration. Methadone does this because it is an opiate agonist and produces cross-tolerance to heroin, whereas naltrexone is an opiate antagonist and blocks heroin's access to brain receptors. Methadone can be given to the physically dependent addict and used to either gradually wean the addict off opiates with gradual decrease in dose. Since it also decreases heroin craving considerably, addicts are more likely to continue methadone treatment. Naltrexone would only be used with addicts that are no longer physically dependent, but because it doesn't reduce the craving for opiates, the person would have to be highly motivated to maintain abstinence.
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