Adverse Effects: The most common adverse effects are drowsiness and sedation which interfere with daytime activity, mental alertness, and reflex actions. Other side-effects include giddiness, ringing in the ears, weariness, fatigue, loss of appetite, nausea, vomiting, rapid pulse, a slight fall in BP, constipation, abdominal pain, dryness of mouth, urinary hasitancy and blurring of vision. Very high doses may induce fever. These adverse effects are more common in elderly people.

Precautions

Alcohol is forbidden with these drugs as sedation of a dangerous level may occur.

Driving and operating any kind of machine should be avoided after taking these drugs as they cause drowsiness.

If taken after a meal, the intensity of side-effects can be minimized.

Drugs containing chlorcyclizine and meclizine which are also antihistaminic, should not be self used by a pregnant woman. These may cause some adverse effects on the foetus.

Ointments containing these drugs should not be used for a prolonged period; allergic reactions have been found to be more common on local application of these drugs. (At times these anti-allergic drugs, when taken orally or more commonly, when applied on the skin, may cause allergic reaction. Is this not a paradox?)

Other Drugs for Symptomatic Treatment

Ketotifen (Ketovent, Ketotif)

This drug stabilizes the cell membranes of mast cells and thus prevents the release of histamine. Besides having antihistaminic properties, it is useful in preventing an attack of asthma. It does, however, cause drowsiness, a dry mouth, dizziness, nausea and weight gain.

Cromolyn Sodium (Ifiral, Fintal)

Used as eye drops (2%) in allergic conjunctivitis, nasal spray (2%) in allergic rhinitis and metered dose inhaler (1 to 2 mg/puff) in bronchial asthma.

Nedocromil

This drug is used 2 puffs, twice a day, in place of cromolyn.

Topical steroids like flunisolide (SYNTARIS) and budesonide (BUDECORT) are nasal spray.

Non-Sedative Antihistaminics for Symptomatic Treatment

These new generation anti-allergic drugs do not reach the brain and do not produce sedation (cetirizine causes some sedation) which is common adverse effects of all the drugs available in this group. These are therefore used more widely. They do not impair psychomotor activities such as driving and do not enhance effects of alcohol or diazepam. They are useful in allergic rhinitis, allergic conjunctivitis, urticaria, drug allergies and atopic eczema. They are not effective in motion sickness, vertigo and should not be used in pregnancy. These agents are less effective than older drugs in common cold.

Decongestants Used in Symptomatic Treatment

These agents reduce the swelling of mucous membranes (shrinking effect) in allergic diseases by constricting small blood vessels. Some drugs are used by mouth such as pseudoephedrine (PSEUDAFED 60 mg tab) and phenylpropanolamine. The latter is rarely used alone.

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