Chlorpheniramine maleate; aka


Chemical formula: C16-H19-Cl-N2.C4-H4-O4

Chlorpheniramine is an anticholinergic antihistamine. It also is effective against nausea and motion sickness, with its primary mechanism of action being its ability to reduce acetylcholine levels in the brain. Acetylcholine is a neurotransmitter. In the brain, acetylcholine and dopamine have antagonistic effects on each other, so a proper balance is necessary for a healthy, functioning body and mind. Many antihistamines (Benadryltm included) work the same way; by reducing (or inhibiting the effects of) the level of acetylcholine in the brain, histamine levels decrease throughout the body, alleviating the symptoms of an allergic reaction. The decrease in acetylcholine gives the dopamine more influence within the brain, which is why anticholinergic drugs are often used to alleviate the symptoms of Parkinson's Disease. Anticholinergics also tend to promote urine retention via temporary swelling of the Prostate, making them useful as anti-incontinence drugs.

Chlorpheniramine is sold under the brand name Chlor-Trimetontm, but it can also be obtained in a far less expensive generic form. I prefer it by itself; it is often included in a cocktail of drugs like acetaminophen and the recently-banned stimulant phenylpropylalamine. Like just about any antihistamine, the side effects include drowsiness or excitability (neurotransmitter action can seem paradoxical to the observer). In my experience, Benadryl (diphenhydramine hydrochloride) is the strongest when it comes to producing these generally undesirable effects. Because of this, most over-the-counter sleep aids contain a small dose of diphenhydramine. Pseudoephedrine gives me a detached feeling and makes me drowsy also, but Chlorpheniramine is just right. I don't notice it one bit.

That doesn't mean it works for everybody. People over 60 are especially likely to suffer from side effects. It's a good idea not to mix Chlorpheniramine with alcohol or any other drug that produces a drowsy effect. This includes sedatives such as Valium, and opiates. This hasn't stopped the pharmaceutical industry from marketing a blend of Chlorpheniramine and Hydrocodone (codeine) for particularily severe colds.

Because it is an anticholinergic, it should not be mixed with any other drugs that are anticholinergics also. If you do, expect side effects like dry mouth and heart palpitations, which are no fun. Some popular anticholinergics are Atropine, Benadryl, the herb Henbane, and the anti-motion-sickness drug Dramamine. Atropine is obtained from the Deadly Nightshade (Belladonna) plant. Its close cousin, Scopolamine, has similar effects (used officially as a patch to treat motion sickness). The anticholinergic effect of Scopolamine is what gives Jimsonweed, Belladonna, and Datura their powerful, psychoactive deliriant effects. I wouldn't recommend taking a mega-dose of Chlorpheniramine for recreational uses, but I have heard of people using Benadryl in such a manner.

Combining Chlorpheniramine with recreational drugs is not a good idea either, simply because it is yet another drug dicking around with the neurotransmitters in your brain. The well-known "This is your brain on dissociatives" FAQ warns that anticholinergics can increase the likelihood of developing Olney's Lesions in the brain when combined with dissociatives like Ketamine, Nitrous Oxide, or Dextromethorphan.

And one last thing -- DO NOT combine Chlorpheniramine with MAOIs, either! MAO inhibitors can drastically prolong and intensify the side effects, which isn't desirable. Some common MAOIs include St. John's Wort, Passionflower (to a lesser degree), Harmala, and Yohimbe / Yohimbine, which is incidentally one of the more powerful and potentially lethal sources.

Update (07-30-02) -- Chlorpheniramine initially didn't bother me, but I began noticing side effects (including a racing heart) and eventually moved on to the nasal steroid Beconase.

Pronunciation: klor-fen-EER-a-meen

Usage: Antihistaminic

Common Dosage: 4 milligrams (mg) every four to six hours

May interact with:


Clarithromycin (e.g., Biaxin)

Erythromycin (e.g., E-Mycin)

Itraconazole (e.g., Sporanox)

Ketoconazole (e.g., Nizoral)

Bepridil (e.g., Vascor)

Disopyramide (e.g., Norpace)

Maprotiline (e.g., Ludiomil)


Pimozide (e.g., Orap)

Procainamide (e.g., Pronestyl)

Quinidine (e.g., Quinaglute Dura-tabs)

Central nervous system (CNS) depressants


HIV-protease inhibitors




Monoamine oxidase (MAO) inhibitors


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