Antiemetics promethazine

Other antiemetics Promethazine (Phenergan) 25 mg PO/IV/rectal suppository Q4H... 

Chlorpromazine, prochlorperazine, promethazine, methylprednisolone, lorazepam, metoclopramide, dexamethasone, or dronabinol may be used for adult patients. Around the clock dosing should be considered. The choice of specific agent should based on patient specific factors, including potential for adverse drug reactions, and cost. SSRIs are effective for breakthrough nausea and vomiting but they are not superior to the less expensive antiemetics above. 

Antagonists. Most of the so-called Hi-antihistamines also block other receptors, including M-cholinoceptors and D-receptors. Hi-antihistamines are used for the symptomatic relief of allergies (e.g., bamipine, chlorpheniramine, clemastine, dimethindene, mebhydroline pheniramine) as antiemetics (meclizine, dimenhydrinate, p. 330), as over-the-counter hypnotics (e.g., diphenhydramine, p. 222). Promethazine represents the transition to the neuroleptic phenothiazines (p. 236). Unwanted effects of most Hi-antihistamines are lassitude (impaired driving skills) and atropine-like reactions (e.g., dry mouth, constipation). At the usual therapeutic doses, astemizole, cetrizine, fexofenadine, and loratidine are practically devoid of sedative and anticholinergic effects. Hj-antihistamines (cimetidine, ranitidine, famotidine, nizatidine) inhibit gastric acid secretion, and thus are useful in the treatment of peptic ulcers. 

Promethazine Promethazine also is indicated for preoperative, postoperative, or obstetric sedation prevention and control of nausea and vomiting associated with certain types of anesthesia and surgery an adjunct to analgesics for control of postoperative pain sedation and relief of apprehension, and to produce light sleep antiemetic effect in postoperative patients active and prophylactic treatment of motion sickness (oral and rectal only). 

Promethazine is not recommended in children younger than 2 years of age. Exercise caution when administering promethazine to children because of the potential for fatal respiratory depression. Limit antiemetics to prolonged vomiting of known etiology. Avoid use in children whose signs and symptoms may suggest Reye syndrome or other hepatic diseases. In children with dehydration, there is an increased susceptibility to dystonias with the use of promethazine. 

B. Two medicines, ipecac and apomorphine, induce vomiting. Metoclopramide is a prokinetic with antiemetic properties and therefore would have the opposite of the desired effect. Morphine is an opioid with analgesic and sedating properties. Promethazine and ondansetron are also antiemetics, not emetics. 

Promethazine (50 mg IM), an antihistaminic with sedative, antiemetic and anticholinergic properties is generally used in children as it causes little respiratory depression. 

Promethazine (Phenergan, etc) 10-25 mg +++ Marked sedation antiemetic block... 

Phenothiazines are antipsychotic agents that can be used for their potent antiemetic and sedative properties (see Chapter 29). The antiemetic properties of phenothiazines are mediated through inhibition of dopamine and muscarinic receptors. Sedative properties are due to their antihistamine activity. The agents most commonly used as antiemetics are prochlorperazine, promethazine, and thiethylperazine. 

All antiemetics are well absorbed from the gastrointestinal tract, with a C 3x of hours following an oral dose. Domperidone, granisetron, ondansetron, prochlorperazine and promethazine undergo extensive first-pass metabolism, which reduces bioavailability. 

All antiemetics have low protein binding, except for domperidone (91-93%) and promethazine (93%), and so are unlikely to be affected by alterations in bilirubin or albumin levels, which may result in an increased free fraction in patients with hypoalbuminaemia or hyper-bilirubinaemia. 

Hepatic adverse effects secondary to antiemetic therapy are usually asymptomatic. Metoclopramide has been reported as causing cholestasis and the formation of arteriovenous shunts in the liver [12]. The 5HTj-receptor antagonists have all been documented as occasionally causing mild increases in liver fimction tests. Cholestatic jaundice has been reported with cyclizine, prochlorperazine and promethazine, and hepatitis has been reported with cyclizine. 

Stool softeners and cathartics can be used in children, as in adults, to relieve symptoms of constipation. Nausea and vomiting generally diminish as opioid therapy is continued, but antihistamines with antiemetic effects, such as hydroxyzine or promethazine, may be helpful as adjuvants to diminish impleasant G1 symptoms. Reducing the opioid dose to minimal analgesic levels may help to limit sedation or drowsiness. Mild respiratory depression, an uncommon side effect in children, may require only that the opioid dose be reduced. 

Antiemetics that act on the vomiting centre have antimuscarinic (their principal mode) and anti-histaminic action (hyoscine, promethazine) they alleviate vomiting from any cause. In contrast, drugs that act on the CTZ (haloperidol, ondansetron) are effective only for vomiting mediated by stimulation of the chemoreceptors (by morphine, digoxin, cytotoxics, uraemia). The most efficacious drugs act at more than one site (Table 31.1). 

Other prophylactic antiemetic agents include clonidine, promethazine, hyoscine, propofol, and metoclopramide. However, the data on these drugs are either insufficient or non-existent. 

A number of the antihistamines, particularly the phenothi-azines and aminoalkyl ethers, have antiemetic actions and thus may be u.seful in the treatment of nausea, vomiting, and motion sickness. Also, those agents that produce pronounced. sedation have application as nonpiescription sleeping aids." - "Several of the phenothiazines have limited u.se in Parkinson-like syndromes as a result of their ability to block central muscarinic receptors." -And. a number of antihistamines, including promethazine, pyrilamine. tri-pelennamine and diphenhydramine, display local anesthetic activity that may be therapeutically useful. ... 

For nausea and vomiting associated with pediatric gastroenteritis, there is greater emphasis on rehydration measures than on pharmacologic intervention. Only two prospective studies have been published on the safety or efficacy of antiemetics in pediatric gastroenteritis since 1966. A recent survey of physicians revealed that promethazine suppositories were the most commonly prescribed antiemetic for pediatric gastroenteritis, despite the lack of prospective trials for this agent. ... 

Phenothiazines (Prototype Promethazine) Most drngs of this class are Hj antagonists and also possess considerable anticholinergic activity. Promethazine, which has prominent sedative effects, and its many congeners are nsed primarily for their antiemetic effects. 

---