Opiates are drugs derived directly from the opium poppy plant. The five main examples are morphine, codeine, thebaine, papaverine, and noscapine. Each occurs naturally in the sap of the poppy (Papaver somniferum), and while they share a common origin, they have very different effects on the body and very different roles in medicine.
The term “opiate” specifically refers to these natural compounds. It’s often confused with “opioid,” which describes lab-made or partially synthesized drugs like oxycodone, fentanyl, and hydrocodone. The distinction matters: all opiates are opioids, but not all opioids are opiates.
Morphine
Morphine is the most well-known opiate and the standard against which other pain medications are measured. It works by binding to a specific type of receptor in the brain and spinal cord, blocking pain signals and producing a strong sense of relief. It remains a foundational treatment for moderate to severe pain, particularly in cancer care, end-of-life palliative settings, and painful crises in sickle cell disease.
Morphine can be given by mouth, injection, or through the spine. Oral doses for someone who hasn’t previously taken opioids typically start at 15 to 30 mg every four hours as needed. Its effectiveness comes with serious risks: it slows breathing, causes constipation by reducing gut movement, constricts the pupils, and creates physical dependence with repeated use. The constipation isn’t mild. Morphine suppresses the nerve signals that push food through the intestines and reduces water flow into the bowel, leading to hard, infrequent stools that often require their own treatment.
In the United States, morphine is classified as a Schedule II controlled substance, meaning it has accepted medical uses but a high potential for misuse.
Codeine
Codeine is a weaker opiate used for mild to moderate pain and, historically, as a cough suppressant in liquid formulations. What makes codeine unusual is that it’s essentially a prodrug: it doesn’t do much on its own. Your liver must convert it into morphine using a specific enzyme called CYP2D6 before it provides meaningful pain relief. Codeine itself binds to pain receptors with roughly 200 times less strength than morphine does.
This reliance on liver metabolism creates a real problem. People who carry certain genetic variations may convert codeine too slowly (getting little pain relief) or too quickly (experiencing dangerously high morphine levels). Genetic testing can identify which group you fall into, but it isn’t routinely done before a prescription is written.
Codeine’s scheduling depends on how it’s formulated. In pure form, it’s Schedule II. Combined with acetaminophen in doses no higher than 90 mg per unit (like Tylenol with Codeine), it drops to Schedule III. Cough syrups with very small amounts, no more than 200 mg per 100 milliliters, are Schedule V, the least restrictive category.
Thebaine
Thebaine is a natural opiate that isn’t used as a medication on its own because it causes stimulant-like effects and seizures rather than pain relief. Its importance is industrial: thebaine is the chemical starting material for manufacturing several widely prescribed semi-synthetic opioids, including oxycodone, hydrocodone, and even naloxone, the overdose-reversal drug. Pharmaceutical companies extract thebaine from poppy crops and chemically modify its structure to produce these other compounds. In that sense, thebaine sits at the crossroads between natural opiates and the synthetic opioid supply chain.
Papaverine
Papaverine stands apart from the other opium alkaloids because it has no pain-relieving or euphoric properties. Instead, it relaxes smooth muscle, the type found in blood vessels, the digestive tract, and the urinary system. It works by raising levels of certain signaling molecules inside muscle cells, which causes them to relax rather than contract.
Doctors use papaverine to treat spasms in the gastrointestinal tract, bile ducts, and ureters. It has also been used to treat erectile dysfunction by relaxing blood vessel walls and improving blood flow. Because it doesn’t activate the brain’s reward pathways the way morphine does, papaverine carries no risk of dependence and isn’t a controlled substance.
Noscapine
Noscapine (sometimes called narcotine, despite not being narcotic) is another non-addictive opium alkaloid. Its primary use has been as a cough suppressant. Like papaverine, it doesn’t produce pain relief or euphoria, and it doesn’t carry the dependence risks of morphine or codeine. Noscapine is more commonly used in some countries outside the United States, and ongoing research has explored its potential in other therapeutic areas, including its effects on cell growth.
How Opiates Differ From Opioids
The five compounds above are the true opiates, all extracted directly from the poppy plant. Drugs you may hear about more often, like oxycodone (OxyContin, Percocet), hydrocodone (Vicodin), hydromorphone (Dilaudid), and fentanyl, are opioids. Some of these are semi-synthetic, meaning they start with a natural opiate like thebaine and are chemically altered in a lab. Others, like fentanyl and methadone, are fully synthetic, designed from scratch to activate the same brain receptors that morphine does.
In everyday conversation, people use “opiate” and “opioid” interchangeably, and most health organizations now use “opioid” as the umbrella term for the entire class. But if someone asks specifically about opiates, they’re asking about what comes from the plant itself.
Shared Risks of Pain-Relieving Opiates
Morphine and codeine, the two opiates prescribed for pain, share a core set of side effects tied to how they activate receptors throughout the body. The most dangerous is respiratory depression: opiates slow the breathing rate by acting on control centers in the brain and on sensors in the airways. At high doses or in combination with alcohol or sedatives, breathing can become irregular enough to be fatal.
Constipation is nearly universal and doesn’t improve with continued use the way other side effects sometimes do. Physical dependence develops with regular use over days to weeks, meaning the body adapts to the drug’s presence. If you stop abruptly, withdrawal symptoms begin within 8 to 24 hours for short-acting opiates like morphine, peaking over the next few days and lasting 4 to 10 days total. Symptoms include muscle aches, anxiety, sweating, nausea, and intense cravings. A longer, milder phase of reduced well-being and cravings can persist for up to six months.
Current CDC guidelines emphasize using the lowest effective dose for the shortest necessary time, maximizing non-opioid alternatives like anti-inflammatory medications, and screening patients for substance use risk before prescribing. These recommendations apply equally to natural opiates and synthetic opioids.