There is this guy... from Dr. Oz.... He only recommends the grapefruit juice (but he also says lemon works...in his book), but he does not go into the drug interactions.

He claims if you eat 30 grams of protein within 1 hr of getting up in the morning you will lose fast. Also there are other things...
He uses beans and legumes instead of other carbs. I bought his book on Amazon --The 4 hr Body: I've lost about 25 lbs since Feb using his ideas.

http://neurotalk.psychcentral.com/thread144410.html

In the book he also recommends alot of spinach... claims he has evidence that it improves the action of insulin at the cell receptors. So I have been doing that too. Eating his way, you don't really get hungry, if you do it correctly. For your protein, he says you can do protein shakes. But you have to avoid most sugars, including fruit on his plan.

I typically have eggs with meat, some spinach and some salsa mixed in a bowl for breakfast. Or with beans. I use black beans, because they don't upset my GI tract. I also use Edamame for dinner, or in the mix, or lentils. Watch your carbs with the foot swelling. High carb intake irregardless of calories for the day...if most are carb you are not going to loose even if the cals are low.... leads to swelling.
One advantage to all the beans, etc, is that they are high in magnesium, and that is helping my blood pressure, and other issues too. A can of black beans typically lasts me 3 meals. About a buck a can (or .92 at Walmart).

The drug most affected by the citrus would be your amitriptyline.
Gabapentin probably not, because it is not metabolized in the body. You should plug in your drugs into the drug checker at
http://www.drugs.com/drug_interactions.html

I have been using the lotion, suggested on the Magnesium cream thread recently. And it is taking down my foot edema dramatically.
It is CVS Epsom lotion. It might work for you.