"The grapefruit juice effect",grapefruit marmalade,a risky business

Its January and that means its grapefruit time in the Algarve,This year there seems to be a bumper crop and I have just been given some gorgeous ruby red grapefruits from a friend who grows them. I just adore grapefruit and I thought I would kick the marmalade season off by attempting something I have never tried before, a grapefruit marmalade. I was first introduced to this bitter,sour somewhat exotic fruit at a hotel breakfast table in the sixties.They're big, they´re sour, have tough membranes, big seeds and bitter flesh. People used to douse them in sugar and prise the flesh out with a special knife or spoon specifically designed for this purpose, just to get one little morsel...of an acquired taste.No,no,no this fruit deserves more respect than that.
But the poor grapefruit has been getting a bad rap over the last couple of years.Research has shown us that the number of drugs that can be risky when taken with grapefruit is on the rise.There are now more than 85 drugs that may interact with grapefruit. The list includes some statins that lower cholesterol (such as atorvastatin, lovastatin, and simvastatin), some antibiotics, cancer drugs, and heart drugs. Most at risk are older people who use more prescriptions and buy more grapefruit.
This is what happens: Grapefruit contains furanocoumarins, which block an enzyme that normally breaks down certain medications in the body. When it is left unchecked, medication levels can grow toxic in the body.
It’s not just grapefruits, either. Other citrus fruits such as Seville oranges (often used in marmalade), limes, and pomelos also contain the active ingredients (furanocoumarins), but have not been as widely studied.
Far from being the harbinger of bad news, I want all of you to enjoy the fruits of this wonderful pamplemousse, so if you were not previously aware of this issue,which came to me via one of our guests,please before you proceed, just check online or with your GP if you are on medication, enjoy eating grapefruit, and want to make this recipe.

Ruby red grapefruit and ginger marmalade 
The added colour of the fruit gives a lovely blush to the finished marmalade, so try to find the ruby red variety rather than just a pink one. 
Makes 2.5kg (5-6lb)
Preparation time 1 hour
Cooking time about 3 hours
1 kg (2lbs) ruby red grapefruit,washed and quartered
1 lemon,washed and quartered
2 litres(31/2 pints
1.5kg (3lb) granulated sugar
2 teaspoons of ground ginger and 100g(4oz) of chopped crystallised ginger preserved in syrup

Peel the grapefruits and lemon quarters.Remove the pips and tie them in a muslin bag.If the peel is really thick,remove most of the pith and put it in the bag also.
Cut the peel finely and place it in a large preserving pan with the chopped pulp and two types of ginger.Add the muslin bag and water.Bring to the boil and then simmer until the peel is soft.About 1-2 hours.
Remove the muslin bag.add the sugar and stir until dissolved.Bring to the boil and boil rapidly until setting point is reached-about 20-30 minutes.Remove any scum from the surface.
Ladle into cool sterilised jars and seal.Label and store.