Opiates are a group of naturally occurring compounds derived from the juice of the poppy Papaver somniferum. Morphine and codeine are classic opiate derivatives used widely in medicine; heroin (diacetylmorphine) is a well-known semi-synthetic, highly addictive street narcotic. The term opioid refers to opiates and semi-synthetic derivatives of naturally occurring opium (eg, morphine, heroin, codeine, and hydrocodone) as well as new, totally synthetic opiate analogs (eg, fentanyl, butorphanol, meperidine, and methadone [Table II–47]). A wide variety of prescription medications contain opioids, often in combination with aspirin or acetaminophen. Dextromethorphan is an opioid derivative with potent antitussive but no analgesic or addictive properties. Tramadol (Ultram) is an analgesic that is unrelated chemically to the opiates but acts on mu-opioid receptors and blocks serotonin reuptake. Butorphanol is available as a nasal spray with rapid absorption. Buprenorphine is a partial opioid agonist that is approved for the treatment of opioid addiction. Suboxone is a sublingual tablet containing buprenorphine plus naloxone to reduce intravenous abuse. Tapentadol (Nucynta) is a mu-opioid agonist that also inhibits the reuptake of norepinephrine. The alkaloid mitragynine is the active component of kratom found in the Southeast Asian tree Mitragyna speciosa Kroth; it has stimulant and opioid-like effects, and has been used for self-treatment of opioid withdrawal.
TABLE II–47.OPIATES AND OPIOIDSa |Favorite Table|Download (.pdf) TABLE II–47. OPIATES AND OPIOIDSa
|Drug ||Type of Activity ||Usual Adult Dosea (mg) ||Elimination Half-life (h) ||Duration of Analgesia (h) |
|Buprenorphine ||Agonistb ||2–8 ||20–70 ||24–48 |
|Butorphanol ||Mixed ||2 ||5–6 ||3–4 |
|Codeine ||Agonist ||60 ||2–4 ||4–6 |
|Fentanyl ||Agonist ||0.2 ||1–5 ||0.5–2 |
|Heroinc ||Agonist ||4 ||N/Ac ||3–4 |
|Hydrocodone ||Agonist ||5 ||3–4 ||4–8 |
|Hydromorphone ||Agonist ||1.5 ||1–4 ||4–5 |
|Loperamide ||Agonist ||4–16 ||9–14 ||Unknown |
|Meperidine ||Agonistd ||100 ||2–5 ||2–4 |
|Methadone ||Agonist ||10 ||20–30 ||4–8e |
|Morphine ||Agonist ||10 ||2–4 ||3–6f |
|Nalbuphine ||Mixed ||10 ||5 ||3–6 |
|Oxycodone ||Agonist ||4.5 ||2–5 ||4–6f |
|Oxymorphone ||Agonist ||1–10 ||7–11 ||3–6f |
|Pentazocine ||Mixed ||50 ||2–3 ||2–3 |
|Propoxypheneg ||Agonist ||100 ||6–12 ||4–6 |
|Tapentadol ||Agonisth ||50–100 ||4 ||4–6 |
|Tramadol ||Agonistd ||50–100 ||6–7.5 ||4–6 |
In general, opioids share the ability to stimulate a number of specific opiate receptors in the CNS, causing sedation and respiratory depression. Death results from respiratory failure, usually as a result of apnea or pulmonary aspiration of gastric contents. In addition, acute noncardiogenic pulmonary edema may occur by unknown mechanisms. In addition to its opioid-like effects, kratom may also stimulate postsynaptic alpha-2 adrenergic and serotonergic (5HT2A) receptors.
Pharmacokinetics. Usually, ...