Antihistamines sedating

Cyclizine has antimuscarinic properties and is a potent anti-emetic, effective for the control of postoperative and drug-induced nausea and vomiting. It has been used to prevent motion sickness, although diphenhydramine and promethazine are more effective. It is available in oral and parenteral formulations. In contrast to many other first-generation antihistamines sedation is not marked. It is available in tablet form as the hydrochloride and in injectable form as the lactate. Because of its anticholinergic action, blurred vision and dry mouth are associated with clinical doses. When given by rapid intravenous injection tachycardia may be a problem. Meclozine is a related drug which, like cyclizine, is used primarily for motion sickness. 

The principal adverse effect of older first-generation antihistamines, sedation, is avoided by use of newer second-generation drugs which do not enter the CNS. 

The sedation side effect commonly observed on administration of classical antihistaminic drugs has been attributed in part to the ease with which many of these compounds cross the blood brain barrier. There have been developed recently a series of agoits, for example, terfenadine (198), which cause reduced sedation by virtue of decreased penetration into the CNS. This is achieved by making them more hydrophilic. Synthesis of a related compound, ebastine (197),... 

Drowsiness and sedation are common adverse reactions seen with the use of many of the antihistamines. Some antihistamines appear to cause more drowsiness and sedation than others. These dm may also have varying degrees of anticholinergic (cholinergic blocking) effects, which may result in dryness of the mouth, nose, and throat and a thickening of bronchial secretions. Several newer preparations (eg, loratadine) cause little, if any, drowsiness and fewer anticholinergic effects than some of the other antihistamines. Hiotosensitivity may occur with the use of the antihistamines. 

The nurse usually gives tiiese drug in die outpatient setting. If the patient is in the hospital or clinic, the nurse observes the patient for die expected effects of die antihistamine and for adverse reactions. The nurse reports adverse reactions to the primary health care provider. In some instances, drowsiness or sedation may occur. When the drug is given to relieve preoperative anxiety, these adverse reactions are expected and are allowed to occur. 

I Older adults are more likely to experience anticholinergic effects (eg, drynessofthe mouth, nose, and throat), dizziness sedation, hypotenson, and confusion from the antihistamines A dosage reduction may be necessary if these symptoms persist. 

Use of codeine may result in respiratory depression, euphoria, light-headedness, sedation, nausea, vomiting, and hypersensitivity reactions. The more common adverse reactions associated with the antitussives are listed in the Summary Drug Table Antitussive, Mucolytic, and Expectorant Drugs. When used as directed, nonprescription cough medicines containing two or more ingredients have few adverse reactions. However, those that contain an antihistamine may cause drowsiness. 

Histamine H,-antagonists For intravenous infusion diphenhydramine, dimetindene and ciemastine are avaiiabie. There are no controiied studies for the new non-sedating antihistamines in the treatment of anaphyiaxis... 

The belief that histamine (HT) has a central effect stems from the knowledge that all the classical antihistamines (Hi receptor antagonists) used to treat allergic reaction, such as hay fever, caused marked sedation if, like mepyramine and promethazine, they can cross the blood-brain barrier, but fail to do so if, like terfenedine and cetirizine, they do not. 

Although histamine has mixed excitatory and inhibitory effects on central neurons, those antihistamines (Hi-receptor antagonists) that enter the brain produce sedation this indicates that the predominant overall effect of histamine is excitatory. The preferred explanation for this rests on evidence that histaminergic neurons in the posterior hypothalamus are active in waking and silent in deep SWS and REM sleep. 

A series of novel l-substituted-4-phenyl-l,2,3-triazolo(4,3-a)quinazolin-5(4H)-ones 1 were synthesized by the cyclization of 2-hydrazino-3-phenyl-quinazolin-4(3H) 2 with various one carbon donors. The starting material 2-hydrazino-3-phenylquinazolin-4(3H)-one 2, was synthesized from aniline 7 by a novel innovative route. When tested for their in vivo Hi-antihistaminic activity on conscious guinea pigs all the test compounds protected the animals from histamine-induced bronchospasm significantly, whereas the compound l-methyl-4-phenyl-l,2,3-triazolo(4,3-a)quinazolin-5(4H)-one lb (percentage protection 70.7%) was found to be equipotent with the reference standard chlorpheniramine maleate (percentage protection 71%). These compounds show negligible sedation (5%) when compared to the reference standard (26%). Hence they could serve as prototype molecules for future development [1,4,5]. 

As sedation is one of the major side effects associated with antihistamines, the test compounds were also evaluated for their sedative potentials. This was determined by measuring the reduction in locomotor activity using an ac-tophotometer [6,7]. The test compounds and the reference standards (chlorpheniramine maleate and cetirizine) were administrated orally at a dose of 5 mg/kg in 1% CMC. 

FDA for chronic use up to 6 months.33 Although not first line-agents for insomnia, sedating antihistamines are prescribed commonly, and the number of prescriptions has increased dramatically over the last 20 years.34 These and other therapies, detailed below, are used to treat insomnia. 

Antihistamines such as diphenhydramine are known for their sedating properties and are frequently used over-the-counter medications (usual doses 25-50 mg) for difficulty sleeping. Diphenhydramine is approved by the FDA for the treatment of insomnia and can be effective at reducing sleep latency and increasing sleep time.43 However, diphenhydramine produces undesirable anticholinergic effects and carryover sedation that limit its use. As with TCAs and BZDRAs, diphenhydramine should be used with caution in the elderly. Valerian root is an herbal sleep remedy that has inconsistent effects on sleep but may reduce sleep latency and efficiency at commonly used doses of 400 to 900 mg valerian extract. Ramelteon, a new melatonin receptor agonist, is indicated for insomnia characterized by difficulty with sleep onset. The recommended dose is 8 mg at bedtime. Ramelteon is not a controlled substance and thus may be a viable option for patients with a history of substance abuse. 

Patients who may benefit from allergen immunotherapy include those who do not tolerate traditional drug therapy (e.g., nosebleeds with intranasal steroids or sedation with antihistamines), suffer from severe symptoms, have comorbid conditions (e.g., asthma or sinusitis), fail drug therapy, or prefer not to take long-term medication. 

These qualities make cromolyn an option for patients with multiple comorbidities and concomitant medications. Cromolyn is an alternative for patients in whom antihistamines are too sedating and impair work and school performance. Additionally, cromolyn helps to prevent AR when taken prior to exposure, such as visiting a home with a pet.18 Due to its excellent safety profile, cromolyn is a first-line agent in children with AR.11,12... 

First-generation antihistamines are effective, but associated sedation and psychomotor impairment limit chronic use. Efficacy and safety of second-generation antihistamines in children have been demonstrated in clinical trials.33 Cetirizine is indicated for children 6 months of age and older, loratadine for children 2 years of age and older, and fexofenadine for children 6 years of age and older.15... 

Is the patient taking antihistamines and/or intranasal steroids Is the patient experiencing adverse effects (e.g., sedation from antihistamines or nasal itching, burning, or bleeding from intranasal corticosteroids) ... 

In addition to sedation, many oral antihistamines can cause hypotension, dizziness, blurred vision, and confusion.28... 

Whether due to their antihistaminic activity or their sedative side effects, pruritus caused by contact dermatitis can be relieved with the use of sedating oral antihistamines such as... 

The hypothesis of the role of HA in wakefulness stems from the observation that administration of the classical antihistamines (i.e. H3 receptor antagonists) induced sedation. These first-generation antihistamines, used to treat inflammatory reactions, could cross the blood-brain barrier and block the central Hi receptor (White Rumbold, 1988). The first study examining the effect of antihistamines on sleep-wakefulness in cats reported an increase in NREM sleep and a decrease in REM sleep (Jewett, 1968). Similar results were also obtained in dogs (Wauquier et ah, 1981) and humans (Risberg et ah, 1975 Bassano Caille, 1979 Nicholson et ah, 1985 Adam Oswald, 1986). Intraventricular application of HA in the anesthetized rat caused a dose-dependent decrease in the duration of narcosis, whereas intraventricular application of HA in conscious... 

Reiner, P. B. Kamondi, A. (1994). Mechanisms of antihistamine-induced sedation in the human brain HI receptor activation reduces background leakage potassium current. Neuroscience 59, 579-88. 

Antihistamines are frequently used, but few clinical studies support their efficacy. A sedating antihistamine (e.g., hydroxyzine, diphenhydramine) can offer an advantage by facilitating sleep because pruritus is often worse at night. 

Medications for symptomatic relief from vertigo consist of antiemetics, benzodiazepines and antihistamines. They are all mostly aimed at the psychological consequences of dizziness and can all have highly unfavourable side effects, for example, sedation, anticholinergic effects and insomnia. The psychological consequences of dizziness in elderly should rather be treated with information about the condition, supportive help actions and increased social activities, than with drugs. 

Synthesis of chlorpromazine, a very sedating phenothiazine antihistamine. ... 

The most significant problems with antihistamines are sedation and weight gain. Except for stimulants, there are no medications that counteract these effects. We do recommend the use of a stimulant to counteract antihistamine effects. 

Significant side effects have been estimated to occur in about 5% of patients on TCAs, most of these effects being attributed to their antimuscarinic properties, for example, blurred vision, dry mouth, tachycardia and disturbed gastrointestinal and urinary tract function. Orthostatic hypotension due to the block of alphai adrenoceptors and sedation resulting from antihistaminic activity frequently occur at therapeutic doses, particularly in the elderly. Excessive sweating is also a fairly common phenomenon, but its precise mechanism is uncertain. In the elderly patient, the precipitation of prostatic hypertrophy and glaucoma by the TCAs is also a frequent cause of concern. 

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