Morphine produces a physical dependence that develops quickly and increases in intensity with increased dosage. When the body's supply of morphine is withheld, withdrawal symptoms occur within a few hours, reaching a peak in intensity within 24 to 48 hours, and then begin to subside. Moreover, the drug produces a rapid tolerance level, a desensitization which requires increasing dosages to achieve the desired effect. Increased dosages produce a greater physical and psychological dependence, resulting in addiction.
Morphine is the main active principle of opium, which contains 10% morphine. It may be extracted either from opium or directly from poppy straw. Morphine is still the classical effective analgesic for the relief of severe pain, but the extent of its use is being challenged by synthetic narcotics which may cause less dependency.