Someone I know feels very jittery after taking NyQuil.  It makes him
unable to sleep.  Despite being very tired, he has to get up and pace
around.  It is very uncomfortable for him.  Is there a particular
ingredient in NyQuil that might be causing this effect?  It is not
acetaminophen because Tylenol does not do this to him.  Thank you for
any help.

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Request for Question Clarification by pinkfreud-ga on 16 Mar 2006 20:39 PST

Is he taking the Nyquil formula with pseudoephedrine, or the one without?

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Clarification of Question by tornado2-ga on 17 Mar 2006 12:16 PST

It is the old formula of NyQuil with pseudoephedrine.

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Request for Question Clarification by pinkfreud-ga on 17 Mar 2006 12:32 PST

There is no way to be certain, but it is possible that your husband's
restlessness is related to pseudoephedrine:

"SIDE EFFECTS: Side effects of antihistamines include drowsiness,
impaired ability to accurately operate machinery, worsening of
glaucoma or asthma or chronic lung diseases, rash, hives,
perspiration, chills dry mouth or throat, low blood counts,
restlessness, ringing in the ears, stomach upset, urinary frequency or
difficulty.

Side effects of pseudoephedrine include stimulation of the nervous
system leading to nervousness, restlessness, excitability, dizziness,
headache, fear, anxiety, tremor, and even hallucinations and
convulsions (seizures)."

http://www.medicinenet.com/chlorpheniramine_pseudoephedrine/article.htm

I'd be glad to gather additional material on the possible side effects
of pseudoephedrine, if that would suffice as an answer.

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Clarification of Question by tornado2-ga on 17 Mar 2006 15:24 PST

Sounds good.  Especially the restlessness and nervousness.  This will
be a good answer, I just wanted to make sure the other ingredients in
NyQuil are not known to have similar symptoms.

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Clarification of Question by tornado2-ga on 17 Mar 2006 15:28 PST

Actually, I suppose he could test this empirically.  We can use your
comment from another one of my posted questions about NyQuil having a
new formula.  If the new formulation, which has all the same drugs
except pseudoephedrine, does not give him the jittery feeling, then we
have our culprit.  Go ahead and post the answer.  I'll have him try
out the new formula and post back.

I've gathered some information about the side effects of
pseudoephedrine, which might be a possible cause of your husband's
jittery symptoms. I'm also posting information on the side effects
associated with Nyquil's other active ingredients. Please be aware
that Google Answers is not a source of authoritative medical advice;
the material I'm providing is for informational purposes, and should
not be viewed as any kind of diagnosis, nor as a subsitute for the
services of a qualified medical professional.

You've indicated that the Nyquil in question is the formulation which
includes pseudoephedrine. Vicks has recently released a
pseudoephedrine-free version of Nyquil. You may be interested in this
FAQ about pseudoephedrine that is posted on the Vicks website:

Vicks: Pseudoephedrine FAQ
http://vicks.com/pseudoephederine_faq.shtml

I happened to have a bottle of the old-formula Nyquil in my medicine
chest, so I looked at the label. These are the active ingredients:

Acetaminophen
Pseudoephedrine hydrochloride
Doxylamine succinate
Dextromethorphan hydrobromide

From MedLinePlus, here's info on possible side effects:

"Although side effects from acetaminophen are not common, they can
occur. Tell your doctor if this symptom is severe or does not go away:

- upset stomach 

If you experience the following symptom, call your doctor immediately: 

- skin rash" 

MedLinePlus: acetaminophen
http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a681004.html#side-effects

"Although side effects from doxylamine are not common, they can occur.
Tell your doctor if this symptom is severe or does not go away:

- dry mouth, nose, and throat 

If you experience any of the following symptoms, call your doctor immediately: 

- vision problems 
- difficulty urinating 
- muscle weakness 
- excitement 
- nervousness" 

MedlinePlus: doxylamine
http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a682537.html#side-effects

"Although side effects from dextromethorphan are not common, they can
occur. Tell your doctor if any of these symptoms are severe or do not
go away:

- dizziness 
- lightheadedness 
- drowsiness 
- nervousness 
- restlessness 
- upset stomach 
- vomiting 
- stomach pain 

If you experience any of the following symptoms, call your doctor immediately: 

- rash 
- high fever 
- persistent headache 
- difficulty breathing 
- mood changes 
- slurred speech" 

MedLinePlus: dextromethorphan
http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a682492.html#side-effects

"Pseudoephedrine may cause side effects. Tell your doctor if any of
these symptoms are severe or do not go away:

- restlessness 
- upset stomach 

Some side effects can be serious. If you experience any of the
following symptoms, call your doctor immediately:

- nervousness 
- dizziness 
- difficulty sleeping 
- stomach pain 
- vomiting 
- difficulty breathing 
- fast or irregular heartbeat 
- weakness 
- palpitations 
- shaking of a part of the body that you cannot control 
- seeing things or hearing voices that do not exist (hallucinating)" 

MedLinePlus: pseudoephedrine
http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a682619.html#side-effects

More on pseudoephedrine as a cause of nervousness or restlessness:

"Pseudoephedrine (Sudafed) is available without prescription, alone or
in combination with other medications in multi-symptom cold and sinus
remedies. Pseudoephedrine can cause insomnia, racing pulse and
jitteriness."

InteliHealth: Acute Sinusitis
http://www.intelihealth.com/IH/ihtIH/WSIHW000/9339/31675.html 

"Common adverse drug reactions (ADRs) associated with pseudoephedrine
therapy include: CNS stimulation, nervousness, excitability,
dizziness, and/or insomnia. Infrequent ADRs include: tachycardia
and/or palpitations. Rarely, pseudoephedrine therapy may be associated
with hallucinations, arrhythmias, hypertension, seizures, and
ischaemic colitis... It has also been reported that pseudoephedrine,
amongst other sympathomimetic agents, may be associated with the
occurrence of stroke."

Wikipedia: pseudoephedrine
http://en.wikipedia.org/wiki/Pseudoephedrine#Adverse_effects 

"Symptoms of toxicity associated with pseudoephedrine include
convulsions, hallucinations, irregular or slow heartbeat, shortness of
breath, trouble breathing, an increase in blood pressure, nervousness,
restlessness, excitement, trouble sleeping, difficult or painful
urination, dizziness, lightheadedness, drowsiness, fast or pounding
heartbeat, increased sweating, nausea, vomiting, trembling, unusual
paleness, or weakness."

California OEHHA: Ephedrine and Pseudoephedrine
http://www.oehha.ca.gov/public_info/pdf/TSD%20Ephedrine%20Meth%20Labs%2010'8'03.pdf

My Google search strategy:

Google Web Search: nyquil ingredients
://www.google.com/search?hl=en&q=nyquil+ingredients

Google Web Search: acetaminophen "side effects"
://www.google.com/search?hl=en&q=acetaminophen+%22side+effects%22

Google Web Search: doxylamine "side effects"
://www.google.com/search?hl=en&q=doxylamine+%22side+effects%22

Google Web Search: dextromethorphan "side effects"
://www.google.com/search?hl=en&q=dextromethorphan+%22side+effects%22

Google Web Search: pseudoephedrine "side effects"
://www.google.com/search?hl=en&q=pseudoephedrine+%22side+effects%22

I hope this is helpful! If anything is unclear or incomplete, please
request clarification; I'll be glad to offer further assistance before
you rate my answer.

Best regards,
pinkfreud

Very good answer.  Thank you.

I think "restlessness" is often noted as a possible side effect for
some anithistamines. So I'd bet that its an antihistamine (like
pseudoephedrine) that's causing the jitteriness when a general
pain-killer (like acetaminophen) doesn't...

Here is some information from Lexi-Comp, which is a highly reliable
resource used by faculty and students at the pharmacy school I attend:

Pseudoephedrine is not actually an antihistamine.  Its pharmacologic
category is an adrenergic agonist.  It stimulates receptors of the
respiratory mucosa to cause vasoconstriction, and also causes
bronchial relaxation.

Pseudoephedrine is known to have the following side effects: 
Nervousness, transient stimulation, insomnia, excitability, dizziness,
drowsiness, convulsions, hallucinations, headache.

There are many other side effects, but these seemed to be the most
pertinent to your question.

I don't know what exact formulation of nyquil we're talking about
here.  If it is the formulation that includes chlorpheniramine and
dextromethorphan, chlorpheniramine is known to cause exitability in
1-10% of people who take it.  Dextromethorphan has very limited side
effects, which do not include insomnia or excitability.

From my experience, I would most likely credit pseudoephedrine as the
problem here.  I would probably try the newer formula without
pseudoephedrine and see if this solves the problem.

Thank you very much for the five stars and the nice tip!

~pinkfreud