Side effect
Encyclopedia
In medicine
, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effect
s, it can also apply to beneficial, but unintended, consequences of the use of a drug
.
Occasionally, drugs are prescribed or procedures performed specifically for their side effects; in that case, said side effect ceases to be a side effect, and is now an intended effect. For instance, X-ray
s were historically (and are currently) used as an imaging technique; the discovery of their oncolytic capability led to their employ in radiotherapy (ablation of malignant tumours).
Use of drugs for unapproved indications—that is, for their side effects—is termed off-label use
. For instance, opioids, which are approved as palliative
treatment for pain
, may also be used for their euphoriant
properties as anxiolytics or antidepressants, whether medically or recreationally
.
Off-label use of drugs, although similar in meaning to side effects, is not to be confused with them; side effects describe the mechanism of action
that a drug used off-label takes, whereas off-label use implies the desired consequences of using a drug for its side-effects.
Off-label use of drugs is legal; the manner in which prescription medication is to be used is solely at the discretion of the prescriber
. However, the marketing of drugs towards unapproved indications is illegal; in fact, several pharmaceutical development firms have been fined for unapproved promotion of their products.
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Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effect
Adverse effect
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
s, it can also apply to beneficial, but unintended, consequences of the use of a drug
Drug
A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
.
Occasionally, drugs are prescribed or procedures performed specifically for their side effects; in that case, said side effect ceases to be a side effect, and is now an intended effect. For instance, X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
s were historically (and are currently) used as an imaging technique; the discovery of their oncolytic capability led to their employ in radiotherapy (ablation of malignant tumours).
Use of drugs for unapproved indications—that is, for their side effects—is termed off-label use
Off-label use
Off-label use is the practice of prescribing pharmaceuticals for an unapproved indication or in an unapproved age group, unapproved dose or unapproved form of administration...
. For instance, opioids, which are approved as palliative
Palliative care
Palliative care is a specialized area of healthcare that focuses on relieving and preventing the suffering of patients...
treatment for pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
, may also be used for their euphoriant
Euphoriant
A euphoriant is a type of psychoactive drug which tends to induce feelings of euphoria, the effects of which may include relaxation, anxiolysis, stress relief, mood lift, pleasure, and a rush although these effects are not necessary for a drug to be a euphoriant. Many euphoriants are notorious for...
properties as anxiolytics or antidepressants, whether medically or recreationally
Recreational drug use
Recreational drug use is the use of a drug, usually psychoactive, with the intention of creating or enhancing recreational experience. Such use is controversial, however, often being considered to be also drug abuse, and it is often illegal...
.
Off-label use of drugs, although similar in meaning to side effects, is not to be confused with them; side effects describe the mechanism of action
Mechanism of action
In pharmacology, the term mechanism of action refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect...
that a drug used off-label takes, whereas off-label use implies the desired consequences of using a drug for its side-effects.
Off-label use of drugs is legal; the manner in which prescription medication is to be used is solely at the discretion of the prescriber
Physician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...
. However, the marketing of drugs towards unapproved indications is illegal; in fact, several pharmaceutical development firms have been fined for unapproved promotion of their products.
Examples of therapeutic side-effects
- BevacizumabBevacizumabBevacizumab is a drug that blocks angiogenesis, the growth of new blood vessels. It is commonly used to treat various cancers, including colorectal, lung, breast, kidney, and glioblastomas....
(Avastin) has been used against wet age-related macular degenerationMacular degenerationAge-related macular degeneration is a medical condition which usually affects older adults and results in a loss of vision in the center of the visual field because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness and visual impairment in older adults...
, as well as macular edemaMacular edemaMacular edema occurs when fluid and protein deposits collect on or under the macula of the eye and causes it to thicken and swell. The swelling may distort a person's central vision, as the macula is near the center of the retina at the back of the eyeball...
from diseases such as diabetic retinopathyDiabetic retinopathyDiabetic retinopathy is retinopathy caused by complications of diabetes mellitus, which can eventually lead to blindness....
and central retinal vein occlusionCentral retinal vein occlusionThe central retinal vein is the venous equivalent of the central retinal artery, and like that blood vessel can suffer from occlusion , similar to that seen in ocular ischemic syndrome...
. - Buprenorphine has been shown experimentally (1982–1995) to be effective against severe, refractory depression.
- BupropionBupropionBupropion is an atypical antidepressant and smoking cessation aid. The drug is a non-tricyclic antidepressant and differs from most commonly prescribed antidepressants such as SSRIs, as its primary pharmacological action is thought to be norepinephrine-dopamine reuptake inhibition...
, an anti-depressant sold as Wellbutrin, is also used as a smoking cessation aid; this indication was later approved, and the name of the smoking cessation product is Zyban. In Ontario, Canada, smoking cessation drugs are not covered by provincial drug plans; elsewhere, Zyban is priced higher than Wellbutrin, despite being the same drug. Therefore, some physicians prescribe Wellbutrin for both indications. - SildenafilSildenafilSildenafil citrate, sold as Viagra, Revatio and under various other trade names, is a drug used to treat erectile dysfunction and pulmonary arterial hypertension . It was originally developed by British scientists and then brought to market by the US-based pharmaceutical company Pfizer...
was originally intended for pulmonary hypertensionPulmonary hypertensionIn medicine, pulmonary hypertension is an increase in blood pressure in the pulmonary artery, pulmonary vein, or pulmonary capillaries, together known as the lung vasculature, leading to shortness of breath, dizziness, fainting, and other symptoms, all of which are exacerbated by exertion...
; subsequently, it was discovered that it produces potentially embarrassing side effectsErectionPenile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal...
, for which it was later marketed. - CarbamazepineCarbamazepineCarbamazepine is an anticonvulsant and mood-stabilizing drug used primarily in the treatment of epilepsy and bipolar disorder, as well as trigeminal neuralgia...
is an approved treatment for manic depression and convulsions, but has side effects useful in treating attention-deficit hyperactivity disorderAttention-deficit hyperactivity disorderAttention deficit hyperactivity disorder is a developmental disorder. It is primarily characterized by "the co-existence of attentional problems and hyperactivity, with each behavior occurring infrequently alone" and symptoms starting before seven years of age.ADHD is the most commonly studied and...
(ADHD), schizophreniaSchizophreniaSchizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
, phantom limbPhantom limbA phantom limb is the sensation that an amputated or missing limb is still attached to the body and is moving appropriately with other body parts. 2 out of 3 combat veterans report this feeling. Approximately 60 to 80% of individuals with an amputation experience phantom sensations in their...
syndrome, paroxysmal extreme pain disorderParoxysmal extreme pain disorderParoxysmal extreme pain disorder , originally named familial rectal pain syndrome, is a rare disorder whose most notable features are pain in the mandibular, ocular and rectal areas as well as flushing. PEPD often first manifests at the beginning of life, perhaps even in utero, with symptoms...
, neuromyotoniaNeuromyotoniaNeuromyotonia , also known as Isaacs' syndrome, is a form of peripheral nerve hyperexcitability that causes spontaneous muscular activity resulting from repetitive motor unit action potentials of peripheral origin.-Causes:...
, and post-traumatic stress disorderPost-traumatic stress disorderPosttraumaticstress disorder is a severe anxiety disorder that can develop after exposure to any event that results in psychological trauma. This event may involve the threat of death to oneself or to someone else, or to one's own or someone else's physical, sexual, or psychological integrity,...
. - DexamethasoneDexamethasoneDexamethasone is a potent synthetic member of the glucocorticoid class of steroid drugs. It acts as an anti-inflammatory and immunosuppressant...
and BetamethasoneBetamethasoneBetamethasone is a potent glucocorticoid steroid with anti-inflammatory and immunosuppressive properties. Unlike other drugs with these effects, betamethasone does not cause water retention. It is applied as a topical cream, ointment, foam, lotion or gel to treat itching...
in premature labor, to enhance pulmonary maturation of the fetus. - DoxepinDoxepinDoxepin is a psychotropic agent with tricyclic antidepressant and anxiolytic properties, known under many brand-names such as Aponal, the original preparation by Boehringer-Mannheim, now part of the Roche group; Adapine, Doxal , Deptran, Sinquan and Sinequan...
has been used to treat Angiodema and severe allergic reactions due to its strong antihistamineAntihistamineAn H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...
properties. - GabapentinGabapentinGabapentin is a pharmaceutical drug, specifically a GABA analogue. It was originally developed for the treatment of epilepsy, and currently is also used to relieve neuropathic pain...
, approved for treatment of seizures and postherpetic neuralgiaPostherpetic neuralgiaPostherpetic neuralgia is a neuralgia caused by the varicella zoster virus. Typically, the neuralgia is confined to a dermatomic area of the skin and follows an outbreak of herpes zoster in that same dermatomic area...
in adults, has side-effects which are useful in treating bipolar disorderBipolar disorderBipolar disorder or bipolar affective disorder, historically known as manic–depressive disorder, is a psychiatric diagnosis that describes a category of mood disorders defined by the presence of one or more episodes of abnormally elevated energy levels, cognition, and mood with or without one or...
, essential tremorEssential tremorEssential tremor is a slowly progressive neurological disorder whose most recognizable feature is a tremor of the arms that is apparent during voluntary movements such as eating and writing...
, hot flashes, migraineMigraineMigraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea...
prophylaxis, neuropathic painNeuropathic painNeuropathic pain results from lesions or diseases affecting the somatosensory system. It may be associated with abnormal sensations called dysesthesia, which occur spontaneously and allodynia that occurs in response to external stimuli. Neuropathic pain may have continuous and/or episodic ...
syndromes, phantom limbPhantom limbA phantom limb is the sensation that an amputated or missing limb is still attached to the body and is moving appropriately with other body parts. 2 out of 3 combat veterans report this feeling. Approximately 60 to 80% of individuals with an amputation experience phantom sensations in their...
syndrome, and restless leg syndrome. - Magnesium sulfateMagnesium sulfateMagnesium sulfate is a chemical compound containing magnesium, sulfur and oxygen, with the formula MgSO4. It is often encountered as the heptahydrate epsomite , commonly called Epsom salt, from the town of Epsom in Surrey, England, where the salt was distilled from the springs that arise where the...
in obstetrics for premature labor and preeclampsia.
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- MethotrexateMethotrexateMethotrexate , abbreviated MTX and formerly known as amethopterin, is an antimetabolite and antifolate drug. It is used in treatment of cancer, autoimmune diseases, ectopic pregnancy, and for the induction of medical abortions. It acts by inhibiting the metabolism of folic acid. Methotrexate...
(MTX), approved for the treatment of choriocarcinomaChoriocarcinomaChoriocarcinoma is a malignant, trophoblastic and aggressive cancer, usually of the placenta. It is characterized by early hematogenous spread to the lungs...
, is frequently used for the medical treatment of an unruptured ectopic pregnancyEctopic pregnancyAn ectopic pregnancy, or eccysis , is a complication of pregnancy in which the embryo implants outside the uterine cavity. With rare exceptions, ectopic pregnancies are not viable. Furthermore, they are dangerous for the parent, since internal haemorrhage is a life threatening complication...
. - The SSRI medication sertralineSertralineSertraline hydrochloride is an antidepressant of the selective serotonin reuptake inhibitor class. It was introduced to the market by Pfizer in 1991. Sertraline is primarily used to treat major depression in adult outpatients as well as obsessive–compulsive, panic, and social anxiety disorders in...
is approved as an anti-depressant, but delays conjugal climaxEjaculationEjaculation is the ejecting of semen from the male reproductory tract, and is usually accompanied by orgasm. It is usually the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. In rare cases ejaculation occurs because of prostatic disease...
in men, and thus may be supplied to those in which climax is prematurePremature ejaculationPremature ejaculation is a condition in which a man ejaculates earlier than he or his partner would like him to. Premature ejaculation is also known as rapid ejaculation, rapid climax, premature climax, or early ejaculation....
. - Human chorionic gonadotropinHuman chorionic gonadotropinHuman chorionic gonadotropin or human chorionic gonadotrophin is a glycoprotein hormone produced during pregnancy that is made by the developing embryo after conception and later by the syncytiotrophoblast .. Some tumors make this hormone; measured elevated levels when the patient is not...
is a hormone produced during pregnancy by the cells that form the placenta. It has been used as a diet hormone as well because of the supposed positive side effects it has on weight loss.