Unfortunately, by law, no veterinarian can advise on dosages of medications without having actually examined the pet.
Xanax has been used a bit in cats but the side effects can be very variable and you don't always get the response you want.
If your cats are very drugged on Ace, it may be that the dose is too high. I would advise trying a lesser dose of this drug.
My favorite drug for reducing anxiety is valium. It works a bit better than Ace although it does cause muscle weakness so while they are on it, you need to make sure to keep them away from stairs, etc. I would call and ask your vet if you can try this drug instead. Many vets carry it in the office but he/she may be able to call it into a pharmacy also.
Any drug will be variable depending on the animals metabolism. Both of your cats, even though they weigh the same, may need different doses. Since there are high and low range doses for all medications, I would recommend trying a test dose at home prior to the vet visit, and then work with your vet over the phone to get a dose that is going to work for both cats.
Sorry I can't provide dosing information for you. I hope this has still been helpful.
Good questions....the Ace may have caused weakness because it was a bit too much for them. Usually it is just supposed to remove anxiety, although the problem with that drug in cats is that fear and stress can over ride the effects. It also tends to make them jumpy and over reactive. It lowers the blood pressure too, so I don't like using it in older cats. Low blood pressure can decrease blood flow to the organs (and many older kitties already have kidney disease) and it can cause a drop in body temp (and many older cats can't regulate the temp as well).
Valium is not only a sedative, but it also relaxes the muscles so they aren't as tense. This is why it can be used in seizuring animals too. I like it because it doesn't mess with the blood pressure and is generally considered safe.
Most general pain medications can be used at the same time as these drugs.
If your cats get extremely stressed, have you ever considered finding a vet who does cats only? Sometimes the environment is much more quiet and although I am certainly not trying to be sexist, most cat only vets are females and many cats respond bettter to them. Try http://www.catvets.com/
Since you mentioned that one of your cats is a senior, I will attach the handout we use at our feline-only clinic for all senior kitties.
Senior Cat Care
Cats age at a different rate than humans. During the first year of life, a cat achieves adulthood. Therefore, that first year is equivalent to about 18 human years. After that, the cat ages in a fairly linear fashion. Each year then becomes the equivalent to about 5 human years. Based on this aging scheme, any cat over 8-10 years of age is deemed a "senior" cat.
Many senior cats get a bit lazy in their grooming habits. They often begin to develop mats in their hair coat. Therefore, frequent (1-3 times per week) brushing is important. Brushing collects the dead hair that would normally be removed by grooming, and it breaks down tangles before they become mats. However, occasionally it will be necessary to cut out a mat. Be very careful with scissors or clippers because many elderly cats have very thin skin that cuts or tears easily.
Senior cats also lose the desire or ability to sharpen their nails regularly. The nails become very thick because the dead nail tissue is retained. Failure to sharpen nails can also result in the nail curling backward into the footpad. This will be most uncomfortable and will result in lameness and bleeding. The key to preventing these problems is to cut your cat's nails at least once each month.
Dental disease is common in older cats. The two most common forms of dental disease are tartar buildup, with resulting periodontal disease, and deep cavities near the gum line. Tartar buildup is common in cats of any age, but older cats often have heavy tartar buildup due to years of dental neglect. The tartar irritates the gums, pushes the gums away from the roots of the teeth, and fosters growth of bacteria. Bacteria not only affect the mouth but they are also carried by the blood stream to other organs, most notably the heart and kidneys. Tartar buildup and periodontal disease are very treatable with proper cleaning and antibiotic therapy. Cavities that form at the gumline (gingiva) are called cervical line lesions. As they form, they may become covered by the gums; the gum then continues to proliferate over them. The cat's mouth is very painful when that tooth is touched and it may have difficulty eating. The only realistic treatment is extraction of the tooth. Attempts have been made to fill these cavities, but invariably these teeth undergo further deterioration and need to be extracted a few weeks to months later. Remember that dental disease is uncomfortable and potentially compromising to the overall health of your cat.
Geriatric cats do not usually lose their eyesight, although it can become diminished, especially in dim lighting situations. However, the irises (the colored part of the eye that opens and closes) often begin to get a mottled appearance at about 15 years of age.
The ears often are afflicted with two problems. Hearing loss and outright deafness occur in many cats over 16 years of age. It is permanent. Excessive wax production is the more common problem. Many older cats have very waxy ears that need cleaning about once each month. A wax solvent may be used; it is put in the ears the first few days of each month or possibly every other month.
Arthritis occurs in the spine or legs of some geriatric cats. It causes them to become reluctant, or even unable, to jump on and off furniture; they may be hesitant to climb stairs. We are limited in the drugs that can be used safely in arthritic cats, so a close examination and discussion of options is important.
Diabetes (more correctly called diabetes mellitus) is a disease caused by the failure of the pancreas to produce adequate insulin. Insulin is required to move blood sugar (glucose) from the blood into the cells. It results in excess urine production, increased thirst, weight loss, and a ravenous appetite. Although these signs should be present in all diabetic cats, some of them may be missed. This is especially a problem when cats go outside because they may eat, drink, and urinate outdoors. If you have several cats and they all eat and drink together, increased thirst or urine production in one cat will easily be missed. Longhaired cats can lose a substantial amount of weight without immediate detection. If you suspect that any of these signs are occurring, your cat needs a blood test to determine its blood glucose level. It is most accurate if your cat has not eaten for at least 6 hours. This is a treatable disease.
Chronic kidney failure is the result of many years of slow deterioration in kidney function. Kidney infections, certain toxins, and congenital diseases may be part of this deterioration process, but aging is the major factor. Something has to wear out first, and in many cats it is the kidneys. Cats in kidney failure are actually producing an excess amount of urine in an attempt to remove waste products that are accumulating in the blood. This results in increased thirst. Gradual weight loss is also common, and loss of appetite occurs as the disease progresses. It can be diagnosed with some simple blood and urine tests. It is manageable if treatment begins before the kidney failure is advanced. While the process can be slowed and the cat made to feel better, the kidneys are not restored to normal.
Hyperthyroidism is due to an enlargement of the thyroid gland. This gland controls the body's rate of metabolism so metabolic functions are accelerated. The first sign is weight loss followed by an increase in appetite as the cat tries to "catch up." As the disease progresses (over several weeks to months), increased thirst and urination, vomiting, diarrhea, hyperactivity, and lack of sleep may also occur. It is diagnosed by feeling for thyroid gland enlargement and some simple blood tests. The good news is that 98% of the time, the enlargement is not due to a cancer; therefore, this is a very treatable, and curable, disease.
High blood pressure, more accurately called hypertension, is fairly common in senior cats. Most of the time it is secondary to either chronic kidney failure or hyperthyroidism. However, it appears that a few cats may have "essential" or "primary" hypertension. This means that there is not an underlying disease; essential hypertension is common in humans. This disease is suspected in cats with the two underlying diseases and is diagnosed by measuring the cat's blood pressure. Because the cat's arteries are so small, a special instrument is required. The most common one used is based on the Doppler principle. Hypertension is very treatable.
Cancer is another common disease in senior cats. There are so many forms of cancer that it is impossible to list specific clinical signs. The signs will be determined by the parts of the body that are affected. Therefore, weight loss, anemia, lethargy, loss of appetite, vomiting, diarrhea, difficulty breathing and coughing are all possible. However, it is unlikely that all of those would occur in any one cat.
Early detection is the key to successful treatment of all of these diseases. Most of them can be controlled or cured if diagnosed early enough. We recommend a panel of tests for our senior patients. These tests begin with a thorough history of your cat's past and present health. Next, a thorough physical examination is performed. Finally, we perform a blood and urine panel that includes specific tests for diabetes, chronic kidney failure, and hyperthyroidism. Blood pressure is determined. If any of these tests have questionable results, other tests can be added including chest x-rays (radiographs), ultrasound studies, and possible biopsies of suspected abnormal organs.