Chlorpheniramine belongs to a group of medications known as first-generation antihistamines. For adults and children 6 years of age and older, it is used to treat symptoms caused by allergies, including itchy and watery eyes, sneezing, runny nose, and skin rash and irritations. It is also used to manage itchy skin caused by insect bites, and other medical conditions like chicken pox or measles. Chlorpheniramine works by blocking the effects of histamine, a substance released by cells in the body that produce allergy symptoms.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

For allergic rhinitis, the usual dose for adults and children 12 years of age and over is 4 mg every 4 to 6 hours.  The maximum recommended dose is 24 mg within a 24-hour period.

For children between 6 and 11 years of age, the usual recommended dose is 2 mg every 4 to 6 hours. The maximum recommended dose is 12 mg within a 24-hour period. This medication is not recommended for children under 6 years of age unless recommended by a doctor.

Seniors may need lower doses of this medication.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as suggested by your doctor or pharmacist. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not take this medication if you:

• are allergic to chlorpheniramine or any ingredients of this medication
• are taking a MAO inhibitor (e.g., phenelzine, tranylcypromine, moclobemide)

Do not give this medication to newborns or premature infants.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• constipation
• diarrhea
• difficulty passing urine
• dizziness
• drowsiness
• dry mouth
• heartburn
• loss of appetite
• nausea
• ringing in the ears
• tiredness
• vaginal dryness
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• confusion
• difficulty sleeping
• excitation
• hallucinations (seeing, hearing, or feeling things that are not there)
• lack of coordination
• nightmares
• painful urination
• restlessness or nervousness
• skin rash or hives
• thickened lung secretions, difficulty breathing
• unusual bruising or bleeding
• vision problems (e.g., blurred vision)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• seizures

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Alcohol and other medications that cause drowsiness: Do not combine this medication with alcohol or other medications (e.g., antidepressants, sleeping pills, anxiety medications) that cause drowsiness since additional drowsiness or suppressed breathing can occur and be dangerous and possibly life-threatening.

Drowsiness/reduced alertness: This medication may cause drowsiness. Avoid driving or operating machinery until you have determined that you do not become drowsy during the day or experience impaired mental or physical abilities while taking this medication.

Liver function: If you have reduced liver function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Medical conditions: If you have any of the following medical conditions, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed:

• angle-closure glaucoma
• chronic lung conditions such as asthma, chronic bronchitis, or emphysema
• enlarged prostate
• heart disease
• obstructed bladder
• obstruction of the intestines
• peptic ulcer disease
• seizures

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk, but it does not appear to have serious or harmful effects on breast-feeding infants. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children less than 6 years old.

Seniors: Seniors may experience more side effects (e.g., drowsiness, dry mouth, difficulty urinating) with this medication. This medication should be not be used by seniors unless recommended by a doctor, pharmacist, or other health care professional.

There may be an interaction between chlorpheniramine and any of the following:

• aclidinium
• alcohol
• amantadine
• amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
• antihistamines (e.g,. azelastine, cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine)
• antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• atropine
• barbiturates (e.g., phenobarbital, pentobarbital)
• benzodiazepines (e.g., lorazepam, diazepam)
• betahistine
• botulinum toxin
• brimonidine
• bupropion
• cannabis
• chloral hydrate
• clarithromycin
• clonidine
• darifenacin
• disopyramide
• domperidone
• donepezil
• entacapone
• erythromycin
• esketamine
• flibanserin
• fluoxetine
• galantamine
• general anesthetics (medications used to put people to sleep before surgery)
• glucagon
• glycopyrrolate
• hydrochlorothiazide
• ipratropium
• ketoconazole
• ketotifen
• lemborexant
• magnesium sulfate
• metoclopramide
• mirabegron
• mirtazapine
• monoamine oxidase inhibitors (MAOIs; e.g., moclobemide, phenelzine, tranylcypromine)
• muscle relaxants (e.g., baclofen, cyclobenzaprine, methocarbamol, orphenadrine)
• narcotic pain relievers (e.g., codeine, fentanyl, morphine, oxycodone, tapentadol, tramadol)
• nitroglycerin
• oxybutynin
• paroxetine
• pitolisant
• pomalidomide
• potassium chloride
• pramipexole
• quinidine
• quinine
• rivastigmine
• rotigotine
• scopolamine
• seizure medications (e.g., clobazam, ethosuximide, levetiracetam, phenobarbital, phenytoin, primidone, rufinamide, topiramate, valproic acid, zonisamide)
• solifenacin
• thalidomide
• thiazide diuretics (e.g., hydrochlorothiazide, indapamide, metolazone)
• tiotropium
• tipranavir
• tolterodine
• tricyclic antidepressants (e.g., amitriptyline, nortriptyline, desipramine)
• umeclidinium
• valerian
• zolpidem
• zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.