Please select the eligibility criteria that correspond to the clinical trial below.
Title: A Randomized, Double Blind, Placebo Controlled Study to Investigate the Effect of Donepezil and Gabapentin Combination on an Experimental Pain Model in Healthy Subjects
Brief Summary: This study will compare the effects of gabapentin alone, and gabapentin + donepezil given together in two types of experimental electrical pain tests in up to 48 healthy male subjects (after 24 recruited in the first cohort an interim analysis will be performed).

The study is a randomized, double blind, placebo controlled, 3 was cross-over design study with incomplete block design and 4 treatment options. Placebo, gabapentin alone (lower dose and higher dose) or gabapentin (lower dose) with donepezil.


Options:
A: Inclusion Criteria:

* You must have been diagnosed with Diabetic Neuropathic Pain
* Patient has an average daily pain score greater than or equal to 4 on an 11-point Likert scale, and patient or provider feel that a change from the current gabapentin therapy for pain management is warranted
* Patient is currently treated with gabapentin greater than or equal to 900 milligram/day, has been prescribed the current dose for at least 4 weeks, and has been at least 80% compliant with dosing, according to patient report
* Patient must agree not to change dose of gabapentin between Visits 1 and 2
* You must have stable glycemic control

Exclusion Criteria:

* Are judged prior to randomization to be at suicidal risk as defined by a score of 2 or greater on question 9 of the Beck Depression Inventory-II (BDI-II)
* Current diagnosis or history of hemangiosarcoma
* Patients with New York Heart Association Class III or IV symptoms of congestive heart failure
* Patients with uncontrolled narrow-angle glaucoma
* Presence of a current seizure disorder
B: Inclusion Criteria:

1. Male between 18 and 55 years of age inclusive, at the time of signing the informed consent.
2. Body weight ≥ 50 Kilogram (kg) and BMI within the range 18.5-29.9 Killogram per square meter (kg/m2) (inclusive).
3. Healthy as determined by a responsible and experienced physician, based on a medical evaluation including medical history, physical examination, psychiatric history, psychiatric evaluation, laboratory tests and cardiac monitoring.
4. Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), alkaline phosphatase and bilirubin ≤ 1.5x Upper Limit of Normal (ULN)
5. QT duration corrected for heart rate by Bazett's formula (QTcB) or QT duration corrected for heart rate by Fridericia's formula (QTcF) \< 450 milli second (msec).

Exclusion Criteria:

1. The subject has either a previous disease or current medical condition, which as judged by the Investigator, may compromise safety or affect the interpretation of efficacy data.
2. History of known or suspected seizures, including infantile febrile, unexplained significant and recent loss of consciousness or history of significant head trauma with loss of consciousness or a family history (first degree relative) of epilepsy or seizures (fits).
3. Abnormalities in 12-lead Electrocardiogram (ECG)
4. Systolic blood pressure (BP) below 90 or above 160mm Hg, or diastolic blood pressure below 50 or above 100 millimeters of mercury (mmHg).
5. History of sensitivity to any of the study medications
6. History of regular alcohol consumption within 6 months of the study defined as: an average weekly intake of \>21 units. One unit is equivalent to 8 g of alcohol: a half-pint (\~240 millil litre \[ml\]) of beer, 1 glass (125 ml) of wine or 1 (25 ml) measure of spirits.
7. A positive pre-study drug/alcohol screen at the screening visit.
8. Excessive caffeine drinkers (\~5 or more cups a day) .
9. Excessive smokers (\>5 /day)
10. Use of prescription or non-prescription drugs, including vitamins, herbal and dietary supplements (including St John's Wort) within 7 days (or 14 days if the drug is a potential enzyme inducer) or 5 half-lives (whichever is longer) prior to screening, unless in the opinion of the Investigator and GSK Medical Monitor the medication will not interfere with the study procedures or compromise subject safety.
11. Use of any topical steroid or capsaicin preparations in the previous 30 days to screening, unless in the opinion of the Investigator and GSK Medical Monitor the medication will not interfere with the study procedures or compromise subject safety.
12. The subject is needle phobic
13. The subject is unable to tolerate the electrical hyperalgesia model or nerve stimulation, including anxiety or atypical response to the stimulation on the training at the screening visit.
14. The subject does not produce an area of allodynia or hyperalgesia to the electrical hyperalgesia model during the screening session.
15. Subject who, in the investigator/designee's judgement, poses a significant suicide risk. Evidence of serious suicide risk may include any history of suicidal behaviour and/or any evidence of suicidal ideation on any questionnaires e.g. type 4 or 5 on the C-SSRS in the last 6 months.
16. The subject has participated in a clinical trial and has received an investigational product within the following time period prior to the baseline session in the current study: 90 days, 5 half-lives or twice the duration of the biological effect of the investigational product (whichever is longer).
17. Where participation in the study would result in donation of blood or blood products in excess of 500 mL within a 84 day period.
18. A positive pre-study Hepatitis B surface antigen or positive Hepatitis C antibody result within 3 months of screening
19. Unwillingness or inability to follow the procedures outlined in the protocol.
C: Inclusion Criteria:

* Lumbosacral radicular pain based on history and physical exam (e.g. pain radiating into one or both lower extremities, sensory loss, muscle weakness, positive straight leg raising test etc.)
* Numerical Rating Scale leg pain score \> 4 (or if 3/10, greater or equal to back pain)
* MRI evidence of spinal pathology consistent with symptoms

Exclusion Criteria:

* Untreated coagulopathy
* Previous spine surgery
* No MRI study
* Leg pain \> 4 years duration Epidural steroid injection within past 3 years Cauda equina syndrome Previous failed trials with gabapentin or pregabalin Allergic reactions to gabapentin or pregabalin Referrals from surgery for diagnostic injections for surgical evaluation Serious medical or psychiatric that condition that might preclude optimal outcome or interfere with participation, such as the need for uninterrupted anticoagulation.

Pregnancy
D: Inclusion Criteria:

1. Men or women 18 years or older who have experienced pain for at least 6 months, but not more than 5 years after the healing of a herpes zoster skin rash(typically about 4 months after the rash first appears).
2. Patient has a pain intensity score of at least 4 on the 11-point Numerical Rating Scale (NRS). Patients should never be informed of the pain intensity criterion prior to screening or randomization.
3. Patients of child-bearing potential must have a negative serum pregnancy test at screening and a negative follow-up urine pregnancy test at randomization.
4. Patient has a mean baseline week pain intensity score of at least 4 on the 11-point NRS scale at the end of a 1-week baseline period and has completed at least 4 days of daily pain diary entries during the baseline week.
5. Patients must have a minimum washout period of greater than 5 times the half-life of the drug of several medications.
6. Patients currently treated with gabapentin pr pregabalin at screening may be eligible for the study, but must have a tapering period wherein the dose of gabapentin or pregabalin is reduced gradually over a period of 5 days followed by a two day washout prior to the Baseline Week.

Exclusion Criteria:

1. Patients who have previously not responded to treatment for PHN with gabapentin or pregabalin.
2. Patients who previously experienced dose-limiting adverse effects that prevented titration of gabapentin to an effective dose.
3. Patient is a nursing mother.
4. Patient has hypersensitivity to gabapentin.
5. Patient has had neurolytic or neurosurgical treatment for PHN.
6. Patient has severe pain from causes other than PHN.
7. Patient has used injected anesthetics or steroids within 30 days of baseline.
8. Patient has skin conditions in the area affected by the neuropathy that could alter sensation.
9. Patient is in an immunocompromised state.
10. Patient has an estimated creatinine clearance less than 50 ml/min.
11. Patient has had malignancy within past 2 years other than basal cell carcinoma.
12. Patient has had gastric reduction surgery.
13. Patient has severe chronic diarrhea, chronic constipation \[unless attributed to drugs that will be washed out\], uncontrolled irritable bowel syndrome (IBS) or unexplained weight loss.
14. Patient has any abnormal chemistry or hematology results that are deemed by the investigator to be clinically significant.
15. Patient has a history of substance abuse within the past year.
16. Patient has a history of seizure (except for infantile febrile seizure) or is at risk of seizure due to head trauma.
17. Patient has a history of chronic hepatitis B or C, hepatitis within the past 3 months, or HIV infection.
18. Patient has any other clinically significant medical or psychological condition that, in the opinion of the Investigator would jeopardize the safety of the patient or affect the validity of the study results.
19. Continuing use of any concomitant medication excluded by Inclusion Criterion 5.
20. Patient has participated in a clinical trial of an investigational drug or device within 30 days of the screening visit.

Answer: B