Morphine is a naturally occurring opiate, which is generally viewed as the gold standard in pain management. When given at an equivalent dosages studies have shown heroin users can't tell the difference.
It is popular as a recreational drug, though it has poor absorption orally. It is highly efficient when injected for severe pain. Injecting is however not recommended for recreational purposes. Oral consumption is the safest route.
It takes about 1 hour to fully absorb into a persons system when taken orally. It will reduce to about 50% in the person blood stream roughly 3 hours after this.