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Pills And Tabs

Antihistamine or Decongestant; what should I take?

pills and tabs

With all the medications available over-the-counter, it can be confusing to know which medications to take for which symptoms when you have allergies.

Let’s start with definitions:

Antihistamine:  a class of medication that blocks the effect of histamine.  Histamine is a chemical mediator released from primarily Mast cells located in the skin, eye conjunctiva, lungs, GI tract and elsewhere.  Histamine when combined with a H1 histamine receptor causes symptoms of:  itching, pain, mucus secretion, increased blood vessel permeability (swelling), flushing, headache, vasodilation (redness), cough, low blood pressure, increased heart rate, and bronchial constriction.

Antihistamines block these effects and like all medications, can have adverse side effects.  There are different “generations” of antihistamines, just like generations of wi-fi on your phone.  3G, 4G, etc.

First generation (0ld antihistamines) by structural class: 

These help allergies but are limited due to side effects of: sedation (sleepiness), GI upset, impaired cognition, slowed reaction time, decreased alertness, confusion, dizziness, ear ringing (tinnitus), anorexia, nausea, vomiting, diarrhea and constipation.  They may also cause dry mouth, blurry vision, urinary retention, and need to be avoided when drinking alcohol. Some of these are still used, but you may recognize some familiar names that are no longer available.

  • Ethanolamines: Diphenhydramine (Benadryl®), Dramamine® and Tavist®
  • Alkylamines: Chlortrimeton®, Teldrin®, Dimetane®, Polaramine®, Drixoral®, Actifed®, Rynatan®, Triaminic TR®.
  • Ethylenediamines: Pyribenzamine®, PBZ®, Allertoc® and Vasocon-A®
  • Piperazines:  Hydroxyzine (Atarax®, Vistaril®), meclizine (Antivert®)
  • Phenothiazines: Promethazine (Phenergan®), and Temaril®
  • Piperidines: Cyproheptadine (Periactin®) and Trinalin®.

Second-Generation or Nonsedating Antihistamines

These are preferred as they have substantially fewer side effects especially sedation.   They are dosed once or twice daily and are available in different formulations (syrup, dissolving tablet, tablet)  for pediatric and adult patients.

  • Piperadines: Loratadine (Claritin®), desloratadine (Clarinex®), Fexofenadine (Allegra®)
  • Piperazine: Cetirizine (Zyrtec®), levocetirizine (Xyzal®)
  • Acrivastine: Semprex®

Decongestant:  medications that decrease nasal “congestion.”

Nasal sprays: Those that contain oxymetazoline are sold as Afrin,® Dristan®, Vicks Sinus®, etc. These can rapidly decrease nasal stuffiness (within minutes).  It’s important not to overuse these products as a person can develop “rhinitis medicamentosa” where you become dependent on the spray and feel the need to use it frequently to keep the nose decongested. For this reason, I recommend the 1, 2, 3 approach.  One spray into each nostril, 2 times a day for 3 days!  If necessary it can be repeated a few days later.

Tablets:  Pseudoephedrine and phenylephrine are the most common and are marketed as Sudafed®, etc.  While these are effective at decreasing nasal congestion, side effects may include GI upset, agitation, nervousness, dizziness, insomnia and tremor.

Combinations: Some allergy medications come as combinations of antihistamines and decongestants such as Claritin D®, Allegra D®, Clarinex D®, Zyrtec D®, etc.  The “D” stands for the decongestant which is pseudoephedrine.

Wrap Up:  For itchy, drippy, runny nose and sneezing, a second-generation antihistamine works well.  If there is significant nasal stuffiness, the addition of a decongestant makes sense.  For short term, quick relief of nasal blockage, a topical nasal spray decongestant can help. If your allergies are still not controlled, make an appointment with Dr. Zacharisen at Family Allergy & Asthma Care of Montana.  There are many other treatments available to control allergies.  We can help!

This educational information does not take the place of your physician’s advice.

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