Is it safe for an 76 year woman to take 4 zyrtec at once?

In doing some research on this drug, I did find that for urticaria (itching), during trials, they used 60mg doses for 1 week which would equal 6 tabs at a time. the following was copied from the FDA description and prescribing info: Overdosage has been reported with Cetirizine hydrochloride. In one adult patient who took 150 mg of Cetirizine hydrochloride, the patient was somnolent but did not display any other clinical signs or abnormal blood chemistry or hematology results. In an 18 month old pediatric patient who took an overdose of Cetirizine hydrochloride (approximately 180 mg), restlessness and irritability were observed initially; this was followed by drowsiness. The acute minimal lethal oral doses were 562 mg/kg in rats (approximately 460 times the maximum recommended daily oral dose in adults on a mg/m2 basis, or approximately 190 times the maximum recommended daily oral dose in infants on a mg/m2 basis).

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The reason for such high doses is that Cetirizine has a low degree of first-pass metabolism-70% is excreted in the urine (50% as unchanged drug) and 10% in the feces. So half the drug passes through without even being metabolized
This is an incredibly high dose (he has recommended)and I doubt seriously that she will need this much! She probably wont itch because she will be too busy being konked out sleeping!! I would give her just one to try first, and see how she does. It may be enough to work. According to the literature, one 10mg dose is pretty effective for urticaria (or itching) when a wheal of histamine was placed subcutaneously. Which just means that they injected a little blister of histamine under the skin to induce an itching response. Histamine is the substance secreted by the body in response to an allergen that causes the unpleasant allergy symptoms like itching, hence the reason we use "anti-histamine". If she needs more than one dose, you can use your own judgement in giving her more, but know that you can give up to 40mg at a single dose. I'm not sure I would go so far as to recommend a max of 32 pills per day (I think I read he said that you could give 32 as a max?). In any case, in any medicine, it is best to use the least effective amount. Perhaps it would be safe to give that many but she likely wont need or tolerate that many. I think doses like that would really just knock her loopy.
I have seen chlorpheniramine maleate, which is another antihistamine, given by an allergist for allergic response 4 tabs at a time every 4 hours when the normal dose is one 4mg tab every 4-6 hours so that is why I wasnt overly shocked at seeing this kind of dose. The patient for the chlorpheniramine only weighed about 60lbs at the time.
It is hard to know when to trust a new Dr when you dont know them and they throw something at you that sounds so outrageous but do remember that most Drs dont want to be sued and they wont knowingly give something harmful to a patient. In this case, yes, I do trust most Drs unless they are some kind of complete idiot. Drs are human though, and they do make mistakes so it is never wrong to question something that sounds odd! If you are totally uncomfortable with this dose (and I do think it will just konk the poor lady out!), you can always ask what other options are. Has she ever tried hydroxyzine (Vistaril or Atarax are the brand names)? It is great for itching but again, sleepiness is going to be a major side effect. Did the dermatologist say what they thought the etiology was for the itch? Did they give you a diagnosis? I just wonder if it was a medication or a product she may be using on her face-a lotion or soap? If we can eliminate the cause, she wouldnt need to treat the symptoms. I know when I take pain medications like hydrocodone or oxycodone my face, around my nose and mouth especially, itches unmercifully but that is because drugs like these cause a release of histamine. Have you looked up her medications to see if any of them may be possible causes that may be eliminated or changed? I know you said she doesnt take pain pills so perhaps it is one of her other drugs. I would also try eliminating or changing products she may use to the facial area to see if that could be the culprit. Of course, a second opinion is never a bad thing either.