Antiemetic drugs

Content

Introduction

Antiemetics are drugs used to prevent and fight vomiting, scientifically said emesis, also effective against nausea (with or without vomiting).

There is currently a large variety of medicines on the market with anti-emetic properties, capable of blocking the transmission of nerve signals to the area of ​​the brain that controls vomiting, called the “vomiting center”.

These are drugs with different mechanisms of action, often used in combination with each other, available in numerous formulations: tablets, capsules, granules, drops, syrup, suppositories, injectable solutions, chewing gums and patches to be applied to the skin.

Some are over-the-counter medications that can be purchased freely, others are subject to medical prescription or reserved for use in hospitals.

Antiemetics are an "effective weapon against nausea and vomiting of various kinds, but they do not act on the factors that triggered them.

Severe and recurrent episodes of nausea and vomiting, in the absence of obvious causes, could be the signal of the presence of an underlying disease, which must be investigated in order to intervene appropriately.

Types of antiemetics

Antiemetic drugs can be divided into the following classes:

  • antiserotonergics (serotonin 5-HT3 receptor antagonists), such as ondansetron, granisetron and tropisetron.Antiserotonergics are powerful antiemetics that are widely used in the treatment of nausea and vomiting, even severe, caused by chemotherapy and radiotherapy, as well as in the prevention of postoperative nausea and vomiting, caused by drugs used during surgery. They are also used to reduce nausea and vomiting from stomach and intestinal infections (gastroenteritis)
  • antidopaminergics (dopamine D2 receptor antagonists), such as, for example, prochlorperazine, perphenazine, chlorpromazine and haloperidol. Antidopaminergics are effective in controlling postoperative nausea and vomiting and, in association with other antiemetics, in preventing nausea and vomiting from chemotherapy and radiotherapy. Some antidopaminergics are also indicated in the treatment of nausea and vomiting related to migraine and inner ear disorders (labyrinthitis). Domperidone and metoclopramide fall into this class of antiemetics, two prokinetic drugs which, by promoting intestinal transit, are commonly used to combat nausea and vomiting caused by digestive disorders, gastroesophageal reflux disease and delayed stomach emptying (gastroparesis). Domperidone has also been shown to be effective against nausea and vomiting induced by levodopa therapy in people affected by the disease Parkinson's disease
  • antihistamines (histamine H1 receptor antagonists), such as dimenhydrate, cyclizine, cinnarizine and promethazine, normally used to relieve allergy-related disorders. Antihistamines are drugs with moderate anti-emetic effects and are often used in combination with each other. or with other antiemetics.They are particularly indicated in the control of nausea and vomiting associated with disorders of the inner ear and the so-called motion sickness (motion sickness), such as seasickness and car sickness, caused by traveling on means of transport. They are also considered first choice drugs in the treatment of severe and continuous nausea and vomiting during pregnancy (hyperemesis gravidarum), to be used only under medical supervision.
  • antimuscarinics (muscarinic receptor antagonists). Their main indication is the prevention and treatment of motion sickness and vomiting (motion sickness). The most commonly used drug is scopolamine (or hyoscine), also available in the form of gradual release patches to be applied behind the ear. If used at least 2 hours before embarking on a trip, the patches ensure good control of disorders (symptoms ) for at least 3 days
  • NK1 antagonists (Neurokinin1 (NK1) receptor antagonists, such as aprepitant and fosaprepitant. These antiemetics are used in drug-based chemotherapy treatments, such as cisplatin, which can cause highly or moderately violent bouts of nausea and vomiting. to corticosteroids and antiserotonergics, NK1 antagonists guarantee "effective protection from both nausea and vomiting that arise within the first 24 hours of therapy (acute emesis) and from nausea and vomiting that occur after 24 hours, sometimes lasting for more days (delayed emesis) They are also used in the control of postoperative nausea and vomiting
  • benzodiazepines, such as diazepam, alprazolam and lorazepam, commonly used to reduce anxiety and promote sleep.Benzodiazepines are able to effectively combat early nausea and vomiting (anticipatory emesis), which occurs before the chemotherapy session, especially in people who have experienced severe or frequent nausea and vomiting in a previous course of chemotherapy. The anticipatory symptoms, characterized by a strong anxious component, can be triggered by the sight and smell of the environment in which the treatment is carried out or even by the mere idea of ​​having to undergo therapy.
  • corticosteroids (or cortisone), mainly used as anti-inflammatory and immunosuppressive agents. The most commonly used corticosteroid, alone or in combination with other antiemetics, is dexamethasone, which is proven to be effective in the treatment of nausea and vomiting, even delayed, due to chemotherapy. It is also widely used in the prevention of postoperative nausea and vomiting
  • cannabinoids (derivatives of Cannabis). Cannabinoid drugs are considered a backup anti-emetic treatment compared to conventional therapeutic options, to be used for the reduction of nausea and vomiting induced by chemotherapy, radiotherapy and HIV therapy in case traditional anti-emetic treatments are not effective

Undesirable (side) effects of antiemetics

Antiemetics, like all medicines, can cause the appearance of undesirable (side) effects which vary according to the type of drug used.

These are usually mild and transient disturbances which resolve spontaneously with the interruption of therapy.

In general, the most frequent side effects of antiemetics are:

  • drowsiness
  • tiredness and a sense of fatigue (asthenia)
  • headache
  • constipation (constipation)
  • blurred vision
  • dry mouth
  • difficulty urinating (urinary retention)

Antidopaminergics, especially if taken in high doses and for prolonged periods, can cause milk secretion from the nipples of women and men (hyperprolactinaemia) and movement disorders (extrapyramidal effects).

The complete list of side effects of each drug is contained in the package leaflet accompanying each drug, available in digital format on the drug database of the Italian Medicines Agency (AIFA).

Precautions for use

Antiemetics should be taken for limited periods of time, respecting the indications and doses recommended by the doctor or pharmacist and reported in the package leaflet included in each package of medicine.

Some antiemetics are contraindicated in children and elderly people or people with health problems, as well as during pregnancy and breastfeeding.

In addition, they can interfere with many medicines used to treat other ailments, increasing or reducing their effects. Thus, for example, antihistamines, which induce sleepiness, can cause effects similar to overdose when taken at the same time as other drugs with sedative effects, such as some codeine products commonly used for coughing.

Before taking an over-the-counter antiemetic, therefore, it is good to seek the advice of a doctor or pharmacist and carefully read the instructions contained in the package leaflet to avoid improper use with serious consequences for health.

Pregnancy and breastfeeding

Nausea and vomiting in pregnancy, in most cases, can be controlled with simple dietary considerations and lifestyle changes.

If, on the other hand, there are violent and repeated episodes of nausea and vomiting (hyperemesis gravidarum), the situation is more serious, as nausea and vomiting can prevent the expectant mother from eating properly, leading to weight loss, dehydration and metabolic imbalances.In these cases, the doctor or gynecologist should be consulted to evaluate drug therapy, or, in the most serious forms, hospitalization.

The most effective and safe antiemetics in pregnancy are antihistamines (in particular promethazine and dimenhydrate), recommended by the AIFA as first choice drugs. In case of therapy failure, the next choice is represented, in order, by prochlorperazine, chlorpromazine or metoclopramide (anti-dopaminergics), as indicated by the AIFA.

A new drug for the treatment of nausea and vomiting in pregnancy has recently been introduced on the market, which uses a combination of doxylamine (an antihistamine) and pyridoxine, better known as vitamin B6 (whose antinausean effects during gestation are already known. ).

This antiemetic association, new for Italy but already used in other countries for several years, has shown a significant ability to reduce pregnancy nausea and vomiting and is recommended by the guidelines of the American College of Obstetricians Obstetricians and Gynecologists, ACOG) as drug therapy of choice.

Since some antiemetics pass through breast milk, albeit in minimal quantities, before taking them while breastfeeding it is necessary to obtain the advice of the doctor, who may prescribe the suspension of breastfeeding.

Bibliography

Flake ZA, Linn BS, Hornecker JR. Practical Selection of Antiemetics in the Ambulatory Setting. American Family Physician. 2015 Mar 1; 91: 293-6

Fallon R, Boulger S, Fraser C, Moriarty K. Recommended drug options for nausea and vomiting. Prescriber. 2010 February 19; 21: 18-33

In-depth link

Italian Medicines Agency (AIFA). For you and me, mom: guide to the correct use of drugs during pregnancy

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