The Effect of Donepezil on Sedation and Other Symptoms

Inclusion Criteria:

1. Patient with drowsiness/sedation caused by opiate for \> 3 days and its intensity more or equal to 3/10 (0 to 10 scale; 0 = no sedation, 10=worst possible sedation).
2. Patient receiving a regular dose of a strong opioid for the treatment of cancer pain, and no dose changes or dose change within 50% for at least 48 hours.Regular administration, defined as short acting opioids oral or parenteral every 4 hours around clock, slow release oral opioids every 12 hs or 24 hs, or transdermal opioids every 72 hours. Strong opioids include morphine, hydromorphone, methadone, fentanyl, and oxycodone.
3. Patient with relatively intact cognition defined by the Mini Mental State Examination according to age and educational level. A score of 24 or above is usually considered normal.
4. Patient willing to engage in follow up visit with a nurse by phone on day 2-7 (each day), 11 and 15 of the study and to return for follow up visit on day 8 of treatment. If patient is unable to come to clinic, assessment will be performed through telephone.
5. Sexually active females at risk of being pregnant with a negative urine pregnancy test
6. Written consent form signed.
7. Patients are 18 years or older
8. Concurrent radiation treatment (defined as 10 or less fractions for a palliative indication) is allowed
9. Concurrent chemotherapy is allowed, if the first two cycles have been well tolerated (defined as no grade 3 or 4 non-hematological toxicity)

Exclusion Criteria:

1. Major contraindication to donepezil i.e. hypersensitivity to donepezil or piperidine derivatives.
2. Patients in whom a major change in opiate dose, analgesia requirements, anesthetic procedures or general anesthetic is expected over the next seven days.
3. Treatment with anti-cholinergic agents (i.e., glycopyrrolate)
4. Patients taking Methylphenidate.
5. Patients with tube feeding (due to difficulty of accurate assessing some of the symptoms such as appetite and anorexia).
6. History of ongoing arrhythmia causing a rhythm other than a sinus rhythm