Prednisone, Zyrtec, pseudoeffedrine…seems like so many warn “may cause drowsiness” but really mean to warn “stay home in bed and have nightmares. At least you won’t drive off a bridge to avoid the car-eating dragons.”
I know a lot of meth-cookers use over-the-counter drugs, but meth is an amphetaime, not a stimulant - no? I’m specificaly curious what is is about the brain’s chemistry that causes its sensory functions to be altered by antiallergy or antihistamines?
Of the three drugs you’ve listed, Zyrtec (cetirizine HCl) is the most likely to cause hallucinations. Prednisone is a steroid that should have little psychological effect. Pseudoephedrine is a stimulant (adrenergic agonist – simulates the effect of adrenaline) that does not cross the blood-brain barrier and therefore should not cause hallucinations.
Anti-allergy drugs (antihistamines) work by blocking the activity of histamine receptors; histamine is a neurotransmitter responsible for allergic reactions. There are several different histamine receptors in the body, though. Over-the-counter anti-allergy drugs work on all of them, which is why they can cause drowsiness. Prescription anti-allergy drugs tend to be specific for the histamine receptors in the body and are not active in the brain, so they do not cause drowsiness.
Some antihistamines also block the activity of another receptor, the acetylcholine receptor, which is responsible for transmitting many sensory nerve signals. This activity is the main cause of hallucinations from antihistamines. However, Zyrtec has minimal activity at both the histamine and acetylcholine receptors in the brain. It should not cause hallucinations except maybe in overdose. OTC antihistamines, such as Dramamine/Gravol, can cause hallucinations with a normal dose.
BTW, while many anti-allergy medications are marketed as ‘non-drowsy’, the reason is different for some drugs. Newer, mostly Rx, antihistamines do not cause drowsiness because they do not block histamine in the brain (which causes drowsiness). Older OTC antihistamines inherently cause drowsiness; they are only ‘non-drowsy’ if they are formulated with a drug that promotes wakefulness, such as pseudoephedrine.
About the meth cooks: meth cooks use pseudoephedrine as a starting material because it is chemically similar to methamphetamine, and can be made into methamphetamine relatively easily. Methamphetamine is an amphetamine, yes, and it’s also a stimulant. The class of drugs called amphetamines are stimulants, generally because they simulate the activity of adrenaline. Another term is ‘sympathomimetic’, because the drugs simulate the effects of the sympathetic nervous system, which uses adrenaline as a neurotransmitter. (The sympathetic nervous system basically causes all the things you’d associate with an adrenaline rush – dry mouth, dilated pupils, loss of appetite, etc.) Incidentally, ‘amphetamine’ stands for ‘alpha-methyl phenethylamine’ and refers to the chemical structure of the drugs.
The short answer to your last question is that some antihistamines interfere with the chemicals that transmit nerve signals from your eyes to your brain, causing hallucinations.
Given that one of my 2 DXM (dextromethorphan) websites happens to cover a specific OTC prep sold in the US (Coricidin Cough and Cold, URL is http://www.coricidin.org), which contains the antihistamine chlorpheniramine maleate, this question is right up my alley. The anti-allergy drugs you are thinking of are in a class known as anticholinergics. These interfere with acetylcholine (a neurotransmitter in the brain). Put simply, a consequence of taking large doses of anticholinergics is hallucinations. Some plants containing anticholinergics, such as belladonna, and have long been used historically as hallucinogens. Sometimes even in a shamanic context.
Uh…no. Actually Prednisone and related steroids are well-known to cause psychological effects in high doses. In some individuals, even low doses can cause this side effect.
Granted, the side effect in question is not hallucinations - it’s more a matter of screwing with the emotions. People have had psychotic episodes requiring in-patient hospitilization while taking Prednisone although, fortunately, reactions that extreme are rare.
Nothing like being woken up at 2 am by someone on Prednisone who is alternating between screaming in anger and crying inconsolibly over trivial issues.
It REALLY pisses me off that doctors almost never mention the possible psych side effects of this category of steroids. No… it’s better the patient thinks she is going crazy and maybe wind up in a locked psych ward…! :rolleyes: Sure, leave it to the poor ER docs to figure out what the heck is going on and just hope the patient hasn’t gotten so paranoid or incoherent by then that the Prednisone prescription won’t be mentioned.
By the way - this is limited to mostly oral applications. The inhaled version that some asthmatics use very, very, very rarely causes any mental side effects. Which is why inhaled is preferred over oral dose.