You should talk with your healthcare provider prior to taking chlorpheniramine if you have:
- Stomach ulcers
- Gastroesophageal reflux disease (GERD)
- An enlarged prostate (also known as benign prostatic hyperplasia or BPH)
- Difficulty passing urine
- An overactive thyroid (hyperthyroidism)
- Heart disease
- High blood pressure (hypertension)
- Chronic obstructive pulmonary disease (COPD)
- Any allergies, including allergies to food, dyes, or preservatives.
Also, let your healthcare provider know if you are:
- Pregnant or thinking of becoming pregnant (see Chlorpheniramine and Pregnancy)
- Breastfeeding (see Chlorpheniramine and Breastfeeding).
Make sure to tell your healthcare provider about any other medications you are taking, including prescription and non-prescription medicines, vitamins, and herbal supplements.
(Click Precautions and Warnings With Chlorpheniramine to learn more, including information on who should not take the drug.)
Chlorpheniramine is part of a class of drugs called antihistamines. Specifically, it is an H1 receptor antagonist. This means it blocks a specific type of histamine receptor in the body (known as H1 receptors). Since allergic reactions are partly caused by the release of histamine from certain cells in the body, chlorpheniramine can help relieve or prevent allergy symptoms.
Chlorpheniramine also blocks acetylcholine receptors, an action that produces some of the unpleasant side effects of the medication, such as dry mouth or difficulty urinating, but also helps to relieve a runny nose.