Antihistamines drowsiness/sedation

In general, the most common side-effect of antihistaminics is sedation which may be followed by drowsiness, impaired alertness and retarded ability to perform jobs which need high precision and concentration. 

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. 

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. 

Majority of antihistaminic drugs produce variable degree of CNS depression i.e. sedation, drowsiness and sleep. Drugs like diphenhydramine, promethazine are potent sedatives and is often accompanied by inability to concentrate. 

Chlorzoxazone (Paraflex, Parafon Forte DSC, Others) [Skeletal Muscle Relaxant/ANS Drug] Uses Adjunct to rest physical therapy to relieve discomfort associated w/ acute, painful musculoskeletal conditions Action Centrally acting skeletal muscle relaxant Dose Adults. 250-500 mg PO tid-qid Peds. 20 mg/kg/d in 3-4 + doses Caution [C, ] Avoid EtOH CNS depressants Contra Severe liver Dz Disp Tabs SE Drowsiness, tach, dizziness, hepatotox, angioedema Interactions T Effects W/ antihistamines, CNS depressants, MAOIs, TCAs, opiates, EtOH, watercress EMS Use of CNS depressants and concurrent EtOH use can T sedation urine may turn reddish purple or orange OD May cause N/V/D, dizziness, HA, X deep tendon reflexes, hypotension and resp depression symptomatic and supportive, activated charcoal may be effective... 

Faxative abuse in elderly patients results in abdominal pain, as well as fluid and electrolyte imbalance. The chronic misuse of analogs containing large amounts of caffeine may produce rebound headache. Antihistamines may cause sedation and drowsiness, and it is advised that patients do not drive after taking antihistamines. People who are involved in performing skilled jobs should restrict their use of antihistamines and sedatives.99,100... 

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. 

Pharmacodynamic interactions. Many TCAs cause sedation and therefore co-prescription with other sedative agents such as opioid analgesics, antihistamines, anxiolytics, hypnotics and alcohol may lead to excessive drowsiness and daytime somnolence. The majority of TCAs can have undesirable cardiovascular effects, in particular prolongation of the QT interval. A similar risk of QT prolongation arises with many other cardiovascular drugs including amiodarone, disopyramide, procainamide, propa-... 

Certain antihistamines are frequently used in the treatment of anxiety hydroxyzine (Vistaril, Atarax) and dipherdiydramine (Benadryl) (see figure 16-C). They act by blocking histamine receptors in the CNS, causing sedation and thereby reducing anxiety. They can also cause drowsiness and impaired performance. They work... 

The older (first-generation) antihistamines which tend to cause sedation have antimuscarinic side-effects similar to the actions of hyoscine. (Second-generation antihistamines, which generally do not cause drowsiness, do not exert antimuscarinic side-effects and are of no use for motion sickness.)... 

However, a few individuals exhibit drowsiness and other central nervous system side-effects in response to non-sedating antihistamines and even to placebo, and impairment of function, if it occurs, is not always accompanied by subjective feelings of drowsiness. Patients should therefore be warned that these antihistamines may affect driving and other skilled tasks and that excess alcohol should be avoided.)... 

Non-sedating oral antihistamines (acrivastine, cetrizine, loratadine) if necessary these do not normally cause drowsiness. 

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