Understanding How Clemastine Works and What to Tell Your Doctor
You should talk with your healthcare provider prior to taking this medication if you have:
- Chronic obstructive pulmonary disease (COPD)
- An enlarged prostate (also known as benign prostatic hyperplasia, or BPH)
- Difficulty passing urine
- Kidney disease, such as kidney failure (renal failure)
- High blood pressure (hypertension)
- Heart disease
- Difficult passing urine
- An overactive thyroid (hyperthyroidism)
- 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 Clemastine and Pregnancy)
- Breastfeeding (see Clemastine 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 Clemastine to learn more, including information on who should not take the drug.)
Clemastine belongs to a class of drugs called antihistamines. Specifically, it is an H1 receptor antagonist. This means that 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, clemastine can help relieve or prevent allergy symptoms.
Clemastine also blocks acetylcholine receptors, an action which 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.