WebMD’s A to Z Drug Database

February 2, 2026

Thus, there are drugs that act on the heart and that are distinguished further by their ability to alter either the frequency of heartbeat, the force of contraction of the heart muscle, or the regularity of the heartbeat. The increase in resistance to antimicrobial drugs has resulted from their widespread and sometimes indiscriminate use (see also antibiotic resistance). Additional information, however, can be found in separate articles on the different classes of drugs and on certain individual drugs themselves.
They have been and are being explored as potential therapeutic agents in treating depression, post-traumatic stress disorder, obsessive–compulsive disorder, alcoholism, and opioid addiction. Hallucinations and possibly delirium resembling the effects of Datura stramonium can result if the drug is taken in much higher than therapeutic doses. Depressants exert their effects through a number of different pharmacological mechanisms, the most prominent of which include potentiation of GABA or opioid activity, and inhibition of adrenergic, histamine or acetylcholine activity. Examples of these kinds of effects may include anxiolysis, sedation, and hypotension. The Controlled Substances Act of 1970 classified marijuana along with heroin and LSD as a Schedule I drug, i.e., having the relatively highest abuse potential and no accepted medical use.
When that happens, it’s called a drug interaction. When a medication works right, it boosts your health or helps you feel better. Always check with your health care provider before stopping or making changes to the medicines you are taking. If you do start using the drug, it’s likely you’ll lose control over its use again — even if you’ve had treatment and you haven’t used the drug for some time.

Reported use of most drugs remains low among U.S. teens

Regardless of genetics, mental health, or traumatic experiences, social factors play a large role in the exposure to and availability of certain types of drugs and patterns of use.
It also has a way to get rid of drugs, usually though your urine.
Make sure they know all the medicines, vitamins, and supplements you’re taking.
The ability to use botanical chemicals to serve the function of endogenous neurotransmitters may have improved survival rates, conferring an evolutionary advantage.
A drug with the affinity to bind to a receptor but without the efficacy to elicit a response is an antagonist.
When a psychoactive drug enters the user’s body, it induces an intoxicating effect.

Harm-reduction policies were popularized in the late 1980s, although they began in the 1970s counter-culture, through cartoons explaining responsible drug use and the consequences of irresponsible drug use to users. Responsible drug use is emphasized as a primary prevention technique in harm-reduction drug policies. This claim has been disputed, specifically by British researcher David Nutt, professor of neuropsychopharmacology at the Imperial College London, who stated that studies showing benefits for “moderate” alcohol consumption in “some middle-aged men” lacked controls for the variable of what the subjects were drinking beforehand. There are many factors in the environment and within the user that interact with each drug differently. Chemical–ecological adaptations and the genetics of hepatic enzymes, particularly cytochrome P450, have led researchers to propose that “humans have shared a co-evolutionary relationship with psychotropic plant substances that is millions of years old.” The ability to use botanical chemicals to serve the function of endogenous neurotransmitters may have improved survival rates, conferring an evolutionary advantage.

Central nervous system drugs

Despite manufacturer claims, these are chemical compounds rather than “natural” or harmless products. Synthetic cannabinoids, also called K2 or Spice, are sprayed on dried herbs and then smoked, but can be prepared as an herbal tea. People use cannabis by smoking, eating or inhaling a vaporized form of the drug. Signs and symptoms of drug use or intoxication may vary, depending on the type of drug. Sometimes it’s difficult to distinguish normal teenage moodiness or anxiety from signs of drug use.
Thrombi are further defined by their adherence to vessel walls, which in the case of a condition such as atherosclerosis can give rise to thrombosis, in which the thrombus partially impedes the flow of blood through the vessel. For example, when a patient experiences an adverse reaction to a drug, these classification systems allow a physician to readily identify an agent that has comparable efficacy but a different structure or mechanism of action. Drugs used in medicine generally are divided into classes or groups on the basis of their uses, their chemical structures, or their mechanisms of action.
While some “inhalant” drugs are used for medical purposes, as in the case of nitrous oxide, a dental anesthetic, inhalants are used as recreational drugs for their intoxicating effect. Many movements and organizations are advocating for or against the liberalization of the use of recreational drugs, most notably regarding the legalization of marijuana and cannabinoids for medical and/or recreational use. Experts in the United Kingdom have suggested that some psychoactive drugs that may be causing less harm to fewer users (although they are also used less frequently in the first place) are cannabis, psilocybin mushrooms, LSD, and MDMA; however, these drugs have risks and side effects of their own. Production, distribution, sale or non-medical use of many psychoactive drugs is either controlled or prohibited outside legally sanctioned channels by law. Psychoactive drugs are substances that, when taken in or administered into one’s system, affect mental processes, e.g. perception, consciousness, cognition or mood and emotions.

Drugs & Medications A-Z

The “war on drugs” promoted by the United States, however, is now facing increasing criticism. Another issue is that the illegality of drugs causes social and economic consequences for users—the drugs may be “cut” with adulterants and the purity varies wildly, making overdoses more likely—and legalization of drug production and distribution could reduce these and other dangers of illegal drug use. Responsible drug use advocates that users should not take drugs at the same time as activities such as driving, swimming, operating machinery, or other activities that are unsafe without a sober state.

Other drugs that act on the blood include the hypolipidemic drugs (or lipid-lowering agents) and the antianemic drugs.
School-based programs are the most commonly used method for drug use education; however, the success rates of these intervention programs are highly dependent on the commitment of participants and are limited in general.
Several major groups of drugs, notably anesthetics and psychiatric drugs, affect the central nervous system.
Grapefruit juice doesn’t mix badly with every type of drug in these classes of medications.
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.

Risk factors

The phenomenon of resistance, in which infectious agents develop the ability to evade drug effects, has required an ongoing search for different agents. Antimicrobial agents often are effective against a specific microorganism or group of closely related microorganisms, and they often do not affect host (e.g., human) cells. These different classification systems can be confusing, since each drug may be included in multiple classes. WebMD does not provide medical advice, diagnosis or treatment.
The combination of the two drugs can cause intoxication with lower alcohol doses. Depressants are psychoactive drugs that temporarily diminish the function or activity of a specific part of the body or mind. The prevalence of recreational drugs in human societies is widely reflected in fiction, entertainment, and the arts, subject to prevailing laws and social conventions.

Make sure they know all the medicines, vitamins, and supplements you’re taking. When this happens, the amount of drug in your body may increase (similar to taking too much) or decrease (similar to taking too little). Your body has enzymes, such as the cytochrome p450 (CYP) and others, that process many types of medications.

As of 2015,update it is drugs estimated that about 5% of people worldwide aged 15 to 65 (158 million to 351 million) had used controlled drugs at least once. In popular practice, recreational drug use is generally tolerated as a social behaviour, rather than perceived as the medical condition of self-medication. Recreational drug use is the use of one or more psychoactive drugs to induce an altered state of consciousness, either for pleasure or for some other casual purpose or pastime. 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. Psychoactive drugs have different degrees of restriction of availability, depending on their risks to health and therapeutic usefulness, and classified according to a hierarchy of schedules at both national and international levels.
Drug, any chemical substance that affects the functioning of living things and the organisms (such as bacteria, fungi, and viruses) that infect them. Supporting scientific research on drug use and addiction Drugs may act on the digestive system either by affecting the actions of the involuntary muscle (motility) and thus altering movement or by altering the secretion of digestive juices or gastric emptying. An embolus travels in the bloodstream and may become lodged in an artery, blocking (occluding) blood flow.