Drugs Used in the Treatment of Obesity
November 30, 2017Selective Serotonin Re-uptake Inhibitors (SSRIs)
December 1, 2017Drugs Used in Nausea and Vertigo
Vomiting during pregnancy
Nausea in the first trimester of pregnancy is generally mild and does not require drug therapy. On rare occasions if vomiting is severe, short-term treatment with an antihistamine, such as promethazine, may be required. Metoclopramide may be considered as second-line treatments. If symptoms do not settle in 24 to 48 hours then specialist opinion should be sought. Hyperemesis gravidarum is a more serious condition, which requires intravenous fluid and electrolyte replacement and sometimes nutritional support. Supplementation with thiamine must be considered in order to reduce the risk of Wernicke’s encephalopathy.
For indication, dosage, contraindications and available brands refer to drugs acting on gastrointestinal tract.
Postoperative nausea and vomiting
The incidence of postoperative nausea and vomiting depends on many factors including the anaesthetic used, the type and duration of surgery, and the patient’s sex. The aim is to prevent postoperative nausea and vomiting from occurring. Drugs used include some phenothiazines (e.g. prochlorperazine), metoclopramide (but 10-mg dose has limited efficacy and higher parenteral doses associated with greater side-effects), 5HT3 antagonists, antihistamines (such as cyclizine), and dexamethasone. A combination of two antiemetic drugs acting at different sites may be needed in resistant postoperative nausea and vomiting. For indication, dosage, contraindications and available brands refer to drugs acting on gastrointestinal tract.
Motion sickness
Antiemetics should be given to prevent motion sickness rather than after nausea or vomiting develop. The most effective drug for the prevention of motion sickness is hyoscine. A transdermal hyoscine patch provides prolonged activity but it needs to be applied several hours before travelling. The sedating antihistamines are slightly less effective against motion sickness, but are generally better tolerated than hyoscine. If a sedative effect is desired promethazine is useful, but generally a slightly less sedating antihistamine such as cyclizine or cinnarizine is preferred. The 5HT3 antagonists, domperidone, metoclopramide, and the phenothiazines (except the antihistamine phenothiazine promethazine) are ineffective in motion sickness. For indication, dosage, contraindications and available brands refer to drugs acting on gastrointestinal tract.
Other vestibular disorders
Management of vestibular diseases is aimed at treating the underlying cause as well as treating symptoms of the balance disturbance and associated nausea and vomiting. Vertigo and nausea associated with Ménière’s disease and middle-ear surgery can be difficult to treat.Betahistine is an analogue of histamine and is claimed to reduce endolymphatic pressure by improving the microcirculation. Betahistine is licensed for vertigo, tinnitus, and hearing loss associated with Ménière’s disease.
Antihistamines
CINNARIZINE:
Indications: vestibular disorders, such as vertigo, tinnitus, nausea, and vomiting in Ménière’s disease; motion sickness.
Contraindications: prostatic hypertrophy, urinary retention, susceptibility to angle-closure glaucoma, and pyloroduodenal obstruction. Antihistamines should be used with caution in hepatic disease.
Dose and Administration: Vestibular disorders, 30 mg 3 times daily; child 5– 12 years 15 mg 3 times daily. Motion sickness, 30 mg 2 hours before travel then 15 mg every 8 hours during journey if necessary; child 5–12 years, 15 mg 2 hours before travel then 7.5 mg every 8 hours during journey if necessary.
PROMETHAZINE HYDROCHLORIDE:
Indications: nausea, vomiting, vertigo, labyrinthine disorders, and motion sickness.
Contraindications: prostatic hypertrophy, urinary retention, susceptibility to angle-closure glaucoma, and pyloroduodenal obstruction. Antihistamines should be used with caution in hepatic disease.
Dose and Administration: Motion sickness prevention, 20–25 mg at bedtime on night before travel, repeat following morning if necessary; child under 2 years not recommended, 2–5 years 5 mg at night and following morning if necessary, 5–10 years 10 mg at night and following morning if necessary.
Phenothiazines and related drugs
CHLORPROMAZINE HYDROCHLORIDE:
Indications: nausea and vomiting of terminal illness (where other drugs have failed or are not available).
Contraindications: Coma, Lactating Mother, Neuroleptic Malignant Syndrome, Severe Cardiovascular Disease, and Stupor.
Dose and Administration: By mouth, 10–25 mg every 4–6 hours; child 500 micrograms/kg every 4–6 hours (1–5 years max. 40 mg daily, 6–12 years max. 75 mg daily). By deep intramuscular injection initially 25 mg then 25– 50 mg every 3–4 hours until vomiting stops; child 500 micrograms/kg every 6–8 hours (1–5 years max. 40 mg daily, 6–12 years max. 75 mg daily).
Domperidone and metoclopramide
DOMPERIDONE:
Indications: nausea and vomiting, dyspepsia, gastro-oesophageal reflux. Contraindications: prolactinoma, hepatic impairment; where increased gastrointestinal motility harmful; pregnancy.
Dose and Administration: By mouth, adult and child body-weight over 35 kg, 10–20 mg 3–4 times daily; max. 80 mg daily; child body-weight up to 35 kg (nausea and vomiting only), 250–500 micrograms/kg 3–4 times daily; max. 2.4 mg/kg daily. By rectum in suppositories, adult and child body-weight over 35 kg, 60 mg twice daily; child 15–35 kg (nausea and vomiting only), 30 mg twice daily; child body-weight under 15 kg, not recommended.
METOCLOPRAMIDE HYDROCHLORIDE:
Indications: adults, nausea and vomiting, particularly in gastro-intestinal disorders and treatment with cytotoxics or radiotherapy; migraine. Contraindications: gastro-intestinal obstruction, perforation or haemorrhage; 3–4 days after gastro-intestinal surgery; phaeochromocytoma; breast-feeding. Dose and Administration: By mouth or by intramuscular injection or by intravenous injection over 1–2 minutes, nausea and vomiting, 10 mg (5 mg in young adults 15–19 years under 60 kg) 3 times daily; child up to 1 year (up to 10 kg) 1 mg twice daily, 1–3 years (10–14 kg) 1 mg 2–3 times daily, 3–5 years (15–19 kg) 2 mg 2–3 times daily, 5–9 years (20–29 kg) 2.5 mg 3 times daily, 9–14 years (30 kg and over) 5 mg 3 times daily.
5HT antagonists
ONDANSETRON:
Indications: Prevention of Cancer Chemotherapy-Induced Nausea and Vomiting, Prevention of Post-Operative Nausea and Vomiting, Prevention of Radiation-Induced Nausea and Vomiting.
Contraindications: Severe Hepatic Disease, Extrapyramidal Disease.
Dose and Administration: Moderately emetogenic chemotherapy or radiotherapy, by mouth, 8 mg 1–2 hours before treatment or by rectum, 16 mg 1–2 hours before treatment or by intramuscular injection or slow intravenous injection, 8 mg immediately before treatment then by mouth, 8 mg every 12 hours for up to 5 days or by rectum, 16 mg daily for up to 5 days; child, by slow intravenous injection or by intravenous infusion over 15 minutes, 5 mg/m2 immediately before chemotherapy then 4 mg by mouth every 12 hours for up to 5 days. Severely emetogenic chemotherapy, by intramuscular injection or slow intravenous injection, 8 mg immediately before treatment, where necessary followed by 2 further doses of 8 mg at intervals of 2–4 hours (or followed by 1 mg/hour by continuous intravenous infusion for up to 24 hours) then by mouth, 8 mg every 12 hours for up to 5 days or by rectum, 16 mg daily for up to 5 days; alternatively, by intravenous infusion over at least 15 minutes, 32 mg immediately before treatment or by rectum, 16 mg 1–2 hours before treatment then by mouth, 8 mg every 12 hours for up to 5 days or by rectum, 16 mg daily for up to 5 days; child, by slow intravenous injection, 5 mg/m2 immediately before chemotherapy then 4 mg by mouth every 12 hours for up to 5 days.
Other drugs for Ménière’s disease
BETAHISTINE DIHYDROCHLORIDE:
Indications: vertigo, tinnitus and hearing loss associated with Ménière’s disease.
Contraindications: phaeochromocytoma.
Dose and Administration: Initially 16 mg 3 times daily, preferably with food; maintenance 24–48 mg daily; child not recommended.
