Drug Definition, Types, Interactions, Abuse, & Facts

February 2, 2026

The UNGASS marked a shift in the overall drug policy discourse to highlight the public health and human rights dimensions of the world drug problem and to achieve a better balance between supply reduction and public health measures. More than 36 million years of healthy life loss (DALY) were attributable to drug use in 2019. Among the complex mechanisms involved are conversion of the receptors to a refractory (unresponsive) state in the presence of an agonist, so that activation cannot occur, or the removal of receptors from the cell membrane (down-regulation) after prolonged exposure to an agonist. Many receptor-mediated events show the phenomenon of desensitization, which means that continued or repeated administration of a drug produces a progressively smaller effect.

Types of drugs

They are sometimes used in combination with other substances such as alcohol.The most common unsupervised use of antihistamines in terms of volume and percentage of the total is perhaps in parallel to the medicinal use of some antihistamines to extend and intensify the effects of opioids and depressants. Their recreational appeal exists mainly due to their anticholinergic properties, that induce anxiolysis and, in some cases such as diphenhydramine, chlorpheniramine, and orphenadrine, a characteristic euphoria at moderate doses.citation needed High dosages taken to induce recreational drug effects may lead to overdoses. When these are used, effects may include anxiolysis (reduction of anxiety), analgesia (pain relief), sedation, somnolence, cognitive/memory impairment, dissociation, muscle relaxation, lowered blood pressure/heart rate, respiratory depression, anesthesia, and anticonvulsant effects. Depressants are widely used throughout the world as prescription medicines and as illicit substances.

‘Affect’ vs. ‘Effect’

Because this interaction occurs inside the cell, agonists for this receptor must be able to cross the cell membrane. A second receptor-controlled enzyme is phosphodiesterase, which catalyzes the cleavage of a membrane phospholipid, phosphatidylinositol, releasing the intracellular messenger inositol triphosphate. The receptor may control calcium influx through the outer cell membrane, thereby altering the concentration of free calcium ions within the cell, or it may control the catalytic activity of one or more membrane-bound enzymes. In the second mechanism, chemical reactions that take place within the cell trigger a series of responses.

Marijuana, hashish and other cannabis-containing substances

People struggling with addiction usually deny they have a problem and hesitate to seek treatment. If you’re not ready to approach a health care provider or mental health professional, help lines or hotlines may be a good place to learn about treatment. Some commonly inhaled substances include glue, paint thinners, correction fluid, felt tip marker fluid, gasoline, cleaning fluids and household aerosol products. Other examples include ketamine and flunitrazepam or Rohypnol — a brand used outside the U.S. — also called roofie. Examples include methylenedioxymethamphetamine, also called MDMA, ecstasy or molly, and gamma-hydroxybutyric acid, known as GHB. The risk of addiction and how fast you become addicted varies by drug.

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  • Drugs approved for human use are divided into those available only with a prescription and those that can be bought freely over the counter.
  • This herbal dietary supplement can affect many medications for heart disease, HIV, depression, and other conditions.
  • Grapefruit juice doesn’t mix badly with every type of drug in these classes of medications.
  • Several major groups of drugs, notably anesthetics and psychiatric drugs, affect the central nervous system.
  • This article focuses on the principles of drug action and includes an overview of the different types of drugs that are used in the treatment and prevention of human diseases.

Blood-thinning drugs with NSAIDs. Two or more drugs that share an active ingredient. For example, taking a cough medicine (antitussive) and a drug to help you sleep (sedative) could cause the two medications to affect each other.

  • Subcultures have emerged among users of recreational drugs, in addition to alternative lifestyles and social movements among those who abstain from them, such as teetotalism and “straight edge”.
  • It is estimated that worldwide there are almost 14.8 million people who inject drugs, of whom 15.2% live with HIV and 38.8% – with hepatitis C.
  • According to addiction researcher Martin A. Plant, some people go through a period of self-redefinition before initiating recreational drug use.
  • These drugs can produce a “high” similar to marijuana and have become a popular but dangerous alternative.
  • Drug harmfulness is defined as the degree to which a psychoactive drug has the potential to cause harm to the user and is measured in several ways, such as by addictiveness and the potential for physical harm.
  • Sometimes it’s difficult to distinguish normal teenage moodiness or anxiety from signs of drug use.

But most drug labels and patient handouts don’t list every possible drug interaction. Pharmacists are experts on medicine safety, and they can work with your doctors to help you avoid drug interactions. You could show them a list of the meds you’re taking, or bring the medication packages to your appointment. That’s extra important if you have more than one doctor who prescribes medicines for you.
Some people who’ve been using opioids over a long period of time may need physician-prescribed temporary or long-term drug substitution during treatment. Opioids are narcotic, painkilling drugs produced from opium or made synthetically. Club drugs are commonly used at clubs, concerts and parties. Substituted cathinones, also called “bath salts,” are mind-altering (psychoactive) substances similar to amphetamines such as ecstasy (MDMA) and cocaine.

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Taking some drugs can be particularly risky, especially if you take high doses or combine them with other drugs or alcohol. Sometimes called the “opioid epidemic,” addiction to opioid prescription pain medicines has reached an alarming rate across the United States. This class of drugs includes, among others, heroin, morphine, codeine, methadone, fentanyl and oxycodone. These drugs are not all in the same category, but they share some similar effects and dangers, including long-term harmful effects. The effects of these drugs can be dangerous and unpredictable, as there is no quality control and some ingredients may not be known. Help from your health care provider, family, friends, support groups or an organized treatment program can help you overcome your drug addiction and stay drug-free.

Drugs affecting blood

Importantly, a 2019 meta-analysis found that 22% of people with amphetamine-induced psychosis transition to a later diagnosis of schizophrenia. For all of the above reasons, the use of medicinal scopolamine for recreational uses is also observed. Antihistamines are also consumed in combination with alcohol, particularly by youth who find it hard to obtain alcohol.
Desensitization is a reversible process, although it can take hours or days for drugs receptors to recover after down-regulation. (For more information on intracellular signaling molecules, see second messenger and kinase.) Regulation of the concentration of free calcium ions is important because, like cAMP, calcium ions control many cellular functions. This substance in turn releases calcium from intracellular stores, thus raising the free calcium ion concentration.

In negotiations, CMS will consider the selected drug’s clinical benefit, evidence about alternative treatments, the extent to which it addresses unmet medical needs, and its impact on specific populations, including people who rely on Medicare. These drugs accounted for approximately $27 billion in total prescription drug spending under Medicare Part B and Part D, representing about 6 percent of total Part B and Part D spending. The Centers for Medicare & Medicaid Services (CMS) announced the selection of 15 high-cost prescription drugs covered under Medicare Part D and, for the first time, drugs payable under Medicare Part B for the third cycle of the Medicare Drug Price Negotiation Program. A small number of recreational inhalant drugs are pharmaceutical products that are used illicitly, such as anesthetics (ether and nitrous oxide) and volatile anti-angina drugs (alkyl nitrites, more commonly known as “poppers”).
The term affinity describes the tendency of a drug to bind to a receptor; efficacy (sometimes called intrinsic activity) describes the ability of the drug-receptor complex to produce a physiological response. With very few exceptions, in order for a drug to affect the function of a cell, an interaction at the molecular level must occur between the drug and some target component of the cell. The end of the 19th century signaled the growth of the pharmaceutical industry and the production of the first synthetic drugs.

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