Opioids are derivatives from opium, extracted from poppy flowers.  The opiums can be natural (morphine), semi-synthetic (codeine), or synthetic (fentanyl).

For clinical use, the opioids are classified mainly into short acting opioids (lasting few hours) and long acting opioids (lasting 8 to 72 hrs).

Some physicians use only long-acting opioids while others rely on combinations of long-acting and short-acting opioids.  Most pain physicians do not rely only on short-acting only, unless necessary.

Because my patients have chronic, constant pain, it is better to use opioids that last long time, i.e. long-acting opioids.  If your pain is constant, through out the day, you will benefit from medications that last through out the day.  With short-acting opioids, the medication takes effect in 15-20 min, but only lasts 3-4 hrs.  Three-four hours later, you will be back in pain, requiring you to take another pill.  If such is the case, you'll be taking medications every 3-4 hours for total of 6-8 tablets a day.  This is not ideal.

More preferred method is to take a medication once a day (and in case of a patch, every 3 days) and have it last the entire day.  There will not be as many ups and down in your pain, and many patients find the pain control to be smoother.

My preference is to have the patient rely on long acting medications and use short acting medications sparingly, such as when you over did yourself.  Usually, my goal is one long acting opioid along with two or three short acting pill a day.

Many short acting opioids are combined with tylenol (vicodin, percocet, etc).  Alotted amount of tylenol intake is 4 grams a day before liver toxicity becomes a concern.  Recent studies have shown that even 4 grams a day can cause some liver injuries in healthy patients.  This determines how much of each pain medications one can take before tylenol toxicity becomes a problem.  For more articles, click here.