An antiemetic is a drug that is effective against vomiting and nausea. Antiemetics are typically used to treat motion sickness and the side effects of opioid analgesics, general anaesthetics and chemotherapy directed against cancer.

[edit] Types of Antiemetics

Antiemetics include:

• 5-HT₃ receptor antagonists – these block serotonin receptors in the central nervous system and gastrointestinal tract. As such, they can be used to treat post-operative and cytotoxic drug nausea & vomiting.
  • Dolasetron (Anzemet) Dolasetron can be administered in tablet form or in an injection. Tablets are administered one hour before chemotherapy or surgery. Injection is administered 30 minutes before certain chemotherapy or surgery.
  • Granisetron (Kytril, Sancuso) Granisetron can be administered in tablet (Kytril), oral solution (Kytril), or in a single transdermal patch to the upper arm (SANCUSO). Tablet and Oral solution (Kytril) should be administered twice daily up to one hour before chemotherapy with 12 hours between doses. Granisetron in patch form (SANCUSO) should be applied to the upper arm a minimum of 24 to 48 hours before the chemotherapy regimen begins. One patch can be worn for up to 7 days depending on the chemotherapy regimen.
  • Ondansetron (Zofran) Ondansetron is administered in an oral tablet form 30 minutes before chemotherapy. Further doses may be taken 1–2 days after chemotherapy completion.
  • Tropisetron (Navoban) Tropisetron can be administered in oral capsules or in injection form. It is given as a single for 6 days after the first day of chemotherapy.
  • Palonosetron (Aloxi) Palonosetron can be administered in an injection form 30 minutes before chemotherapy regimen begins or immediately before surgery. It can also be administered in oral capsule form one hour prior to the start of chemotherapy.
  • Mirtazapine (Remeron), an antidepressant that also has strong antiemetic effects.
• Dopamine antagonists act in the brain and are used to treat nausea and vomiting associated with neoplastic disease, radiation sickness, opioids, cytotoxic drugs and general anaesthetics.
  • Domperidone
  • Droperidol, haloperidol, chlorpromazine, promethazine, prochlorperazine. Some of these drugs are limited in their usefulness by their extra-pyramidal and sedative side-effects. Prochlorperazine can be administered via a rectal suppository for adults only.
  • Metoclopramide (Reglan) also acts on the GI tract as a pro-kinetic, and is thus useful in gastrointestinal disease; however, it is poor in cytotoxic or post-op vomiting.
  • Alizapride
• Antihistamines (H₁ histamine receptor antagonists), effective in many conditions, including motion sickness and severe morning sickness in pregnancy.
  • Cyclizine
  • Diphenhydramine (Benadryl)
  • Dimenhydrinate (Gravol, Dramamine)
  • Meclizine (Bonine, Antivert)
  • Promethazine (Pentazine, Phenergan, Promacot) Promethazine can be administered via a rectal suppository for adults and children over 2 years of age.
  • Hydroxyzine
• Cannabinoids are used in patients with cachexia, cytotoxic nausea, and vomiting, or who are unresponsive to other agents.
  • Cannabis (Marijuana). Most patients prefer smoked or vaporized cannabis over pharmaceutical versions because they do not contain all 66 cannabinoids that are in cannabis, many of which have medicinal applications. Medical marijuana is also much less expensive than related pharmaceuticals. CBD is a main cannabinoid not in Marinol or Cesamet.
  • Dronabinol (Marinol). Ninety percent of sales are for cancer and AIDS patients. The other 10% of its sales thought to be for pain, Multiple Sclerosis and also for Alzheimer's disease.
  • Nabilone (Cesamet). Put back on the market in late 2006. In the US, it is a Schedule II substance unlike Marinol which is Schedule III and cannabis which is Schedule I.
  • Sativex is an oral spray containing THC and CBD. It is currently legal in Canada and a few countries in Europe but not in the U.S.
• Benzodiazepines
  • Midazolam given at the onset of anesthesia has been shown in recent trials to be as effective as ondansetron, a 5-HT₃ antagonist in the prevention of post-operative nausea and vomiting. Further studies need to be undertaken.
  • Lorazepam said to be very good as an adjunct treatment for nausea along with first line medications such as Compazine or Zofran.
• Anticholinergics
  • Hyoscine (also known as scopolamine)
• Steroids
  • Dexamethasone given in low dose at the onset of a general anaesthetic for surgery is an effective anti-emetic. The specific mechanism of action is not fully understood.
• NK1 receptor antagonist
  • Aprepitant (Emend) Commercially available NK1 Receptor antagonist
  • Casopitant Investigational NK1 receptor antagonist
• Other
  • Trimethobenzamide; thought to work on the CTZ
  • Ginger
  • Emetrol also claimed to be an effective antiemetic.
  • Propofol given intravenously. It has been used in an acute care setting in hospital as a rescue therapy for emesis.
  • Peppermint claimed to help nausea or stomach pain when added into a tea or peppermint candies.
  • Muscimol purported as such^[1]
  • Ajwain purported to be antiemetic. It is a popular spice in India, Ethiopia and Eritrea.
  • Zolpidem has also been reported to be a newer antiemetic that is being used more and more for patients that have been unresponsive to other first-line typical antiemetic. Its mechanism of action when used as an antiemetic (Zolpidem's first-most prescribed on-label use is for the treatment of insomnia; some cancer patients receiving chemotherapy medication, as well as Zolpidem (which at the time was only being used by the patents to help their cancer-related insomnia; and noticed the potentially powerful antiemetic properties of the medicine, which was reported to their doctors). Clinicians have not found a direct link between specific types of nausea and Zolpidem other than various patient reports that appear to show a possible, and potentially powerful and new secondary-use of the medication (off-label at this point). More formal trials will need to be concluded before any detailed results can be analyzed. In the meantime, physicians do seem to be using Zolpidem on a growing basis; usually as a second- or third-line drug after a patient has tried the more prominent antiemetics such as Zofran. Lastly, judging from the fairly small number of actual published reports from physicians using this medication (Probably due to the fact that either a patient's insurance refused to off-label coverage and/or that physicians are less-likely overall to present or publicly generate major "breakthrough" news when they only have treated/access to a small and typically quite limited number of patients. At this time it seems that the main trials and individual, case-by-case usage of this medication for nausea, have been centered in both the United Kingdom and the United States. Also to note, it is not understood, or well-enough studied at this point to say that Zolpidem is a virtually "unknown" antiemetic, but when patients have severe nausea reactions to any number of root causes; ongoing daily treatment with Zolpidem seems to be a worthy medication to explore with the patient.
• Non-pharmaceutical therapies with some evidence of efficacy include acupuncture and hypnosis. All drugs have potential side effects. It is important to try to reduce the baseline risk of nausea and vomiting, particularly with respect to surgery.

[edit] References

[edit] See also

• Emetic
• Hyperemesis gravidarum
• Chemotherapy

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Antiemetic".