Since the mutation is a genetic issue, there is currently no cure for the flush reaction. Clinicians and the East Asian public generally know about the alcohol flushing response. Prevention would include not drinking alcohol.

Among US adults older than 55, 4% are taking medication and or supplements that put them at risk of a major drug interaction. Potential drug-drug interactions have increased over time and are more common in the low educated elderly even after controlling for age, sex, place of residence, and comorbidity.

Around 80% of Asian people (less common in Thailand, Laos and the Indian subcontinent) have a variant of the gene coding for the enzyme alcohol dehydrogenase called "ADH1B", whereas almost all Japanese, Korean and Chinese people have a variant of the gene called "ADH1C", both resulting in an alcohol dehydrogenase enzyme that converts alcohol to toxic acetaldehyde at a much higher efficiency than other gene variants (40- to 100-fold in case of ADH1B).

In about 50% of Asians, the increased acetaldehyde accumulation is worsened by another gene variant, the mitochondrial ALDH2 allele, which results in a less functional acetaldehyde dehydrogenase enzyme, responsible for the breakdown of acetaldehyde. The result is that affected people may be better at metabolizing alcohol, often not feeling the alcohol "buzz" to the same extent as others, but show far more acetaldehyde-based side effects while drinking.

A drug interaction is a situation in which a substance (usually another drug) affects the activity of a drug when both are administered together. This action can be synergistic (when the drug's effect is increased) or antagonistic (when the drug's effect is decreased) or a new effect can be produced that neither produces on its own. Typically, interactions between drugs come to mind (drug-drug interaction). However, interactions may also exist between drugs and foods (drug-food interactions), as well as drugs and medicinal plants or herbs (drug-plant interactions). People taking antidepressant drugs such as monoamine oxidase inhibitors should not take food containing tyramine as hypertensive crisis may occur (an example of a drug-food interaction). These interactions may occur out of accidental misuse or due to lack of knowledge about the active ingredients involved in the relevant substances.

It is therefore easy to see the importance of these pharmacological interactions in the practice of medicine. If a patient is taking two drugs and one of them increases the effect of the other it is possible that an overdose may occur. The interaction of the two drugs may also increase the risk that side effects will occur. On the other hand, if the action of a drug is reduced it may cease to have any therapeutic use because of under dosage. Notwithstanding the above, on occasion these interactions may be sought in order to obtain an improved therapeutic effect. Examples of this include the use of codeine with paracetamol to increase its analgesic effect. Or the combination of clavulanic acid with amoxicillin in order to overcome bacterial resistance to the antibiotic. It should also be remembered that there are interactions that, from a theoretical standpoint, may occur but in clinical practice have no important repercussions.

The pharmaceutical interactions that are of special interest to the practice of medicine are primarily those that have negative effects for an organism. The risk that a pharmacological interaction will appear increases as a function of the number of drugs administered to a patient at the same time. Over a third (36%) of older adults in the U.S. regularly use 5 or more medications or supplements and 15% are potentially at risk for a major drug-drug interaction. Both the use of medications and subsequent adverse drug interactions have increased significantly between 2005-2011.

It is possible that an interaction will occur between a drug and another substance present in the organism (i.e. foods or alcohol). Or in certain specific situations a drug may even react with itself, such as occurs with dehydration. In other situations, the interaction does not involve any effect on the drug. In certain cases, the presence of a drug in an individual's blood may affect certain types of laboratory analysis (analytical interference).

It is also possible for interactions to occur outside an organism before administration of the drugs has taken place. This can occur when two drugs are mixed, for example, in a saline solution prior to intravenous injection. Some classic examples of this type of interaction include that thiopentone and suxamethonium should not be placed in the same syringe and same is true for benzylpenicillin and heparin. These situations will all be discussed under the same heading due to their conceptual similarity.

Drug interactions may be the result of various processes. These processes may include alterations in the pharmacokinetics of the drug, such as alterations in the absorption, distribution, metabolism, and excretion (ADME) of a drug. Alternatively, drug interactions may be the result of the pharmacodynamic properties of the drug, e.g. the co-administration of a receptor antagonist and an agonist for the same receptor.

Drug tolerance is a pharmacological concept describing subjects' reduced reaction to a drug following its repeated use. Increasing its dosage may re-amplify the drug's effects, however this may accelerate tolerance, further reducing the drug's effects. Drug tolerance is indicative of drug use but is not necessarily associated with drug dependence or addiction. The process of tolerance development is reversible (e.g., through a drug holiday) and can involve both physiological factors and psychological factors.

One may also develop drug tolerance to side effects, in which case tolerance is a desirable characteristic. A medical intervention that has for objective to increase tolerance (e.g., allergen immunotherapy, in which one is exposed to larger and larger amounts of allergen to decrease one's allergic reactions) is called drug desensitization.

The opposite concept to drug tolerance is drug reverse tolerance (or drug sensitization), in which case the subject's reaction or effect will increase following its repeated use. The two notions are not incompatible and tolerance may sometimes lead to reverse tolerance. For example, heavy drinkers initially develop tolerance to alcohol (requiring them to drink larger amounts to achieve a similar effect) but excessive drinking can cause liver damage, which then puts them at risk of intoxication when drinking even very small amounts of alcohol.

Drug tolerance should not be confused with drug tolerability, which refers to the degree to which overt adverse effects of a drug can be tolerated by a patient.

Behavioral tolerance occurs with the use of certain psychoactive drugs, where tolerance to a behavioral effect of a drug, such as increased motor activity by methamphetamine, occurs with repeated use; it may occur through drug-independent learning or as a form of pharmacodynamic tolerance in the brain; the latter mechanism of behavioral tolerance occurs when one learns how to actively overcome drug-induced impairment through practice. Behavioral tolerance is often context-dependent, meaning tolerance depends on the environment in which the drug is administered, and not on the drug itself. Behavioral sensitization describes the opposite phenomenon.

Psychotoxicity in pharmacology is the effect when a drug interferes seriously with normal behaviour.

Cocaine can be snorted, swallowed, injected, or smoked. Most deaths due to cocaine are accidental but may also be the result of body packing or stuffing with rupture in the gastrointestinal tract. Use of cocaine causes tachyarrhythmias and a marked elevation of blood pressure (hypertension), which can be life-threatening. This can lead to death from acute myocardial infarction, respiratory failure, stroke, cerebral hemorrhage, or heart failure. Cocaine overdose may result in hyperthermia as stimulation and increased muscular activity cause greater heat production. Heat loss is also inhibited by the cocaine-induced vasoconstriction. Cocaine and/or associated hyperthermia may cause muscle cell destruction (rhabdomyolysis) and myoglobinuria resulting in renal failure. Individuals with cocaine overdose should be transported immediately to the nearest emergency department, preferably by ambulance in case cardiac arrest occurs en route. According to the National Institute on Drug Abuse, approximately 5000 deaths occur annually in the US due to cocaine overdose.

Cocaine increases alertness, feelings of well-being, euphoria, energy, competence, sociability, and sexuality. Common side effects include anxiety, increased temperature, paranoia, restlessness, and teeth grinding. With prolonged use, the drug can cause insomnia, anorexia, tachycardia, hallucinations, and paranoid delusions. Possible lethal side effects include rapid heartbeat, abnormal heart rhythms, tremors, convulsions, markedly increased core temperature, renal failure, heart attack, stroke and heart failure.

Depression with suicidal ideation may develop in heavy users. Finally, a loss of vesicular monoamine transporters, neurofilament proteins, and other morphological changes appear to indicate a long-term damage to dopamine neurons. Chronic intranasal usage can degrade the cartilage separating the nostrils (the septum nasi), which can eventually lead to its complete disappearance.

Studies have shown that cocaine usage during pregnancy triggers premature labor and may lead to abruptio placentae.

Alcohol intolerance is due to a genetic deficiency of the enzyme alcohol dehydrogenase, the enzyme that metabolises ingested alcohol. It can also be an effect or side effect associated with certain drugs such as disulfiram, metronidazole, or nilutamide. It is characterized as intolerance of and unpleasant symptoms upon the ingestion of alcohol, causing hangover symptoms similar to the "disulfiram-like reaction" of aldehyde dehydrogenase deficiency or chronic fatigue syndrome.

If people are intolerant, some nearly non-alcoholic beverages may be a problem, similar to alcohol-containing medications, vinegar, inhalation of alcohol or the vapour of alcohol-containing cleaning agents.

Drinking alcohol first or afterwards together with Calcium cyanamide, an inorganic compound used as a fertilizer, can cause permanent or long lasting intolerance (nitrolime disease), contributing together with other substances to the accumulation of harmful Acetaldehyde by inhibiting the enzyme acetaldehyde dehydrogenase.

The short-term effects of alcohol (also known formally as ethanol) consumption–due to drinking beer, wine, distilled spirits or other alcoholic beverages–range from a decrease in anxiety and motor skills and euphoria at lower doses to intoxication (drunkenness), stupor, unconsciousness, anterograde amnesia (memory "blackouts"), and central nervous system depression at higher doses. Cell membranes are highly permeable to alcohol, so once alcohol is in the bloodstream it can diffuse into nearly every cell in the body.

The concentration of alcohol in blood is measured via blood alcohol content (BAC). The amount and circumstances of consumption play a large part in determining the extent of intoxication; for example, eating a heavy meal before alcohol consumption causes alcohol to absorb more slowly. The amount of alcohol consumed largely determines the extent of hangovers, although hydration also plays a role. After excessive drinking, stupor and unconsciousness can occur. Extreme levels of consumption can lead to alcohol poisoning and death (a concentration in the blood stream of 0.40% will kill half of those affected). Alcohol may also cause death indirectly, by asphyxiation from vomit.

Alcohol can greatly exacerbate sleep problems. During abstinence, residual disruptions in sleep regularity and sleep patterns are the greatest predictors of relapse.

Conditions of fatigue correlate positively with increased alcohol consumption.

Idiosyncratic drug reactions, also known as type B reactions, are drug reactions that occur rarely and unpredictably amongst the population. This is not to be mistaken with idiopathic, which implies that the cause is not known. They frequently occur with exposure to new drugs, as they have not been fully tested and the full range of possible side-effects have not been discovered; they may also be listed as an adverse drug reaction with a drug, but are extremely rare.

Some patients have multiple-drug intolerance. Patients who have multiple idiopathic effects that are nonspecific are more likely to have anxiety and depression.

Idiosyncratic drug reactions appear to not be concentration dependent. A minimal amount of drug will cause an immune response, but it is suspected that at a low enough concentration, a drug will be less likely to initiate an immune response.

A phototoxic substance is a chemical compound which becomes toxic when exposed to light.

- Some medicines: tetracycline antibiotics, sulfonamides, amiodarone, quinolones

- Many cold pressed citrus essential oils such as bergamot oil

- Some plant juices: parsley, lime, and Heracleum mantegazzianum

- Others: psoralen

Several health authorities have issued related guidance documents, which need to be considered for drug development:

- ICH (International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use)

- M3(R2) "Guidance on Nonclinical Safety Studies for the Conduct of Human Clinical Trials and Marketing Authorization for Pharmaceuticals"

- S9 "Nonclinical Evaluation for Anticancer Pharmaceuticals"

- S10 "Photosafety Evaluation"

- EMA (European Medicines Agency)

- "Note for Guidance on Photosafety Testing" (revision on-hold)

- "Question & Answers on the Note for Guidance on Photosafety Testing"

- FDA (U.S. Food and Drug Administration)

- MHLW/PMDA (Japanese Ministry of Health, Labour and Welfare / Pharmaceuticals and Medical Devices Agency)

In adverse drug reactions involving overdoses, the toxic effect is simply an extension of the pharmacological effect (Type A adverse drug reactions). On the other hand, clinical symptoms of idiosyncratic drug reactions (Type B adverse drug reactions) are different from the pharmacological effect of the drug.

The proposed mechanism of most idiosyncratic drug reactions is immune-mediated toxicity. To create an immune response, a foreign molecule must be present that antibodies can bind to (i.e. the antigen) and cellular damage must exist. Very often, drugs will not be immunogenic because they are too small to induce immune response. However, a drug can cause an immune response if the drug binds a larger molecule. Some unaltered drugs, such as penicillin, will bind avidly to proteins. Others must be bioactivated into a toxic compound that will in turn bind to proteins. The second criterion of cellular damage can come either from a toxic drug/drug metabolite, or from an injury or infection.

These will sensitize the immune system to the drug and cause a response.

Idiosyncratic reactions fall conventionally under toxicology.

A longitudinal study done on prenatal stress and gender roles showed that prenatal stress only plays a small part in the gender roles the offspring takes on and mentions it has more to do with older siblings, maternal use of alcohol and/or tobacco, maternal education, and the observance or teaching of “traditional sex roles” from the parents.

CRS is an adverse effect of some drugs and is a form of systemic inflammatory response syndrome.

The Common Terminology Criteria for Adverse Events classifications for CRS as of version 4.03 issued in 2010 were:

Co-carcinogens can be a lifestyle like cigarette-smoking, alcohol-drinking or even areca nut tobacco-chewing, which is an Asian tradition, because those activities promote the cytopathic effect (CPE). Also, some virus are co-carcinogens like Herpesviruses, Epstein–Barr virus (EBV) and human herpesvirus 4 (HHV-4) Epstein–Barr virus destroy immune system for human body and then increase the risk of cancer such as Hodgkin’s lymphoma and human immunodeficiency virus because they cause a long term-chronic inflammation for lymphocytes and epithelial cells. Moreover, Over intake beta carotene for a long period of time increased the risk of lung cancer, prostate cancer and many other kind of malignant tumor for cigarette smoker and worker having high contact with asbestos. Generally, co-carcinogen can be irregular eating habits and disease virus and co-carcinogen not only help cancer cell make malignant tumor but also increase the risk of cardiovascular disease and mortality rate.

Prenatal stress (or prenatal maternal stress) is exposure of an expectant mother to stress, which can be caused by stressful life events or by environmental hardships. The resulting changes to the mother's hormonal and immune system may harm the fetus's (and after birth, the infant's) immune function and brain development.

Prenatal stress is shown to have several affects in fetal brain development. In the hippocampus of adult male rats, prenatal stress has shown to decrease the rate of proliferation and cell death in the hypothalamus-pituitary axis. Prenatal stressed animals have prolonged corticosterone response. Removing the adrenal glands of the mother eliminates the effect of the pup's corticosterone response. Supplementing the adrenalectamized mother with corticosterone, rescued the hypothalamic-pituitary-axis response to maternal stress for prenatally stressed offspring. Prenatal stress caused high glucocorticoids, which in turn affects the hypothalamic-pituitary-axis negative feedback.

A study by García-Cáceres et al. showed that prenatal stress decreases cell turnover and proliferation in the hypothalamus of adult rats, which reduces structural plasticity and reduces the response to stress in adulthood. This study also showed that when prenatally stressed rats were stressed in adulthood the females showed an increase in corticotropin-releasing hormone suggesting it to be an up-regulation in the hypothalamic-pituitary adrenal axis. Males showed no elevation of corticosterone levels. Increase in adrenocorticotropic hormone with no effect of adult stress and a decrease in the corticotropin-releasing hormone mRNA in the hypothalamus showed a down-regulation. The author concludes that this makes prenatally stressed females less reactive to later life stressors than males.

Experiments for human toxicology require a long term following and a large amount of investment in order to classify a chemical as co-carcinogens, carcinogens or anti-carcinogenic. In recent years, people substitutes health supplement for healthy meal. Some myths even state beta carotene as elixir in developing country(The Third World).

With rising health consciousness, people rely on food supplements like vitamins A, B, C, D, E etc. these vitamins act as anti-oxidants chemical in the human body. Antioxidants is a good chemical in the appropriate consumption but a large overdose can cause cellular oxidation and cause cytopathic. Also, the industries can not strictly control the concentration and dose for supplement that extracted from natural food resources. A long-term consumption of those supplement can cause physical burden and also a significant hard work for organ to metabolize. Many health organization and government have published a maximum daily consumption for supplement called Tolerable Upper Intake Levels (UL), for example World Health Organization suggest the Tolerable Upper Intake Levels of Vitamin C is 2000 mg/d for adult men from age 31 to 50. Tolerable Upper Intake Levels is different for different gender and age. These suggested intake level can be followed in order to maintain the public health and safety.

Both animal and human experiment research shows that supplement cannot be the substitution to replace the daily food diet. Having a diverse diet and healthy habits is the better way to stay healthy instead of taking a lots of supplement that might be a co-carcinogen.

Cytokine release syndrome is an adverse effect of some monoclonal antibody drugs, as well as adoptive T-cell therapies. Severe cases have been called "cytokine storms", a term borrowed from discussions of the pathophysiology of immune disorders and infectious disease.

CRS has been known since the approval of the first monoclonal antibody drug, Muromonab-CD3, which causes CRS, but people working in the field of drug development at biotech and pharmaceutical companies, regulatory agencies, and academia began to more intensely discuss methods to classify it and how to mitigate its risk following the disastrous 2006 Phase I clinical trial of TGN 1412, in which the six subjects experienced severe CRS.

Hydrogen narcosis (also known as the hydrogen effect) is the psychotropic state induced by breathing hydrogen at high pressures. Hydrogen narcosis produces symptoms such as hallucinations, disorientation, and confusion, which are similar to hallucinogenic drugs. It can be experienced by deep-sea divers who dive to below sea level breathing hydrogen mixtures. However, hydrogen has far less narcotic effect than nitrogen (which causes the better known nitrogen narcosis) and is very rarely used in diving. In tests of the effect of hydrogen narcosis, where divers dived to with a hydrogen–helium–oxygen (Hydreliox) mixture containing 49% hydrogen, it was found that while the narcotic effect of hydrogen was detectable, the neurological symptoms of high-pressure nervous syndrome were only moderate.

Common adverse drug reactions (≥ 1% of people) associated with use of the penicillins include diarrhoea, hypersensitivity, nausea, rash, neurotoxicity, urticaria, and superinfection (including candidiasis). Infrequent adverse effects (0.1–1% of people) include fever, vomiting, erythema, dermatitis, angioedema, seizures (especially in people with epilepsy), and pseudomembranous colitis.

The EPA lists no evidence for human cancer incidence connected with copper, and lists animal evidence linking copper to cancer as "inadequate". Two studies in mice have shown no increased incidence of cancer. One of these used regular injections of copper compounds, including cupric oxide. One study of two strains of mice fed copper compounds found a varying increased incidence of reticulum cell sarcoma in males of one strain, but not the other (there was a slightly increased incidence in females of both strains). These results have not been repeated.