Today's weapons, tomorrow's targets
Alzheimer's disease is a devastating neurodegenerative disorder that continues to afflict millions of Americans each year. But despite its prevalence, there are no medications on the market to prevent the disease or reverse the damage it causes. This leaves physicians and pharmacists struggling to find the best treatment options.
Pharmacists now are armed with medications that can at best only slow the progression of the disease. However, new disease-modifying drugs on the horizon could change how the disease is attacked and may give pharmacists more therapeutic options.
According to the Alzheimer's Association, an estimated 5.4 million Americans have Alzheimer's disease, and by 2030 the number of Alzheimer's patients 65 years of age or older is expected to grow to 7.7 million.
Current treatment options
Although there are no disease-modifying agents on the market to treat Alzheimer's disease, there are medications that seek to minimize symptoms and slow the disease's progression.
Donepezil HCl (Aricept, Eisai and Pfizer), galantamine (Razadyne, Janssen Pharmaceuticals), rivastigmine (Exelon, Novartis Pharmaceuticals), and tacrine (Cognex, Shionogi Pharma) are all recommended for mild-to-moderate dementia of the Alzheimer's type and from a clinical perspective do not differ greatly, said Jeffery, who also has a practice at the VA Connecticut Healthcare System, where he serves as a pharmacist on a geriatric consult service.
"Sometimes there are some differences in tolerability, so that's one thing that we look at," he said.
Rivastigmine is also distinctive because of its delivery method. In addition to an oral version of the drug, it is also available in a transdermal patch. This option may be helpful in a long-term-care setting for patients who may have difficulty eating or swallowing. Swanoski said that for some patients, the patch could also minimize nausea, a common side effect associated with cholinesterase inhibitors.
Other side effects of cholinesterase inhibitors include loose stools, urinary frequency, incontinence, and vivid dreams.
The final agent used to treat Alzheimer's disease is memantine (Namenda, Forest Laboratories), an N-methyl-D-aspartate (NMDA) receptor antagonist. This drug is indicated for moderate to severe dementia of the Alzheimer's type and can be used alone or in combination with cholinesterase inhibitors.
"There's evidence to show that using the memantine together with the cholinesterase inhibitors is more effective than the cholinesterase inhibitors alone or the memantine alone, but if the patient is not tolerating the cholinesterase inhibitors, memantine is an option to be used by itself," Swanoski said.
Memantine works by blocking glutamate action.
A side effect of the medication is constipation; however, Jeffery said, pharmacists also need to be cognizant of the patient's drug regimen when administering this drug. "This is a renally eliminated drug, so you have to watch for somebody's creatinine clearance, and generally if it's less than 30, you have to make some adjustments and drugs that will alkalize the urine will decrease the clearance," he said.