CiSRA Puzzle Competition 2013 - Solutions

4B. Interactions

Assembling the jigsaw pieces from Group 4 for this puzzle gives the following:

solution image

The puzzle text represents what is essentially a classic style logic puzzle. Eight people are named. From the information the pharmacist gives, it is possible to use logic to determine:

The names of the people who came in that morning.
An interesting characteristic of each person.
The order they were served.

A common approach for solving this kind of logic puzzle is to use a grid. Each piece of information can be worked through by putting a tick in every known association, and a cross in every impossible pairing. The following is a brief description of one possible chain of logic to solve it.

First, there are some connections which are given in the clues reasonably directly:

Dickens = 8th (i.e. last)
Puggsworth = 1st
Irving = Beach (sunbaking) = 3rd (as he's after whoever was after Mr Puggsworth)
Klacid = 8th

There's a lot of information about Mr Easton. One line describes the people either side of him, and shortly after is a description of someone earlier still and someone later still. This gives the following sequence to build from (the '?' describes a possible but not necessary gap):

?, Calcium, ?, Drunk, Easton, Grapefruit, ?, Asthmatic, ?

This also means that none of these characteristics apply to Mr Easton. From other clues, the person taking Klacid was the last person (so not Easton), Beach is explicitly given as Irving, and Easton is explicitly mentioned as not allergic to penicillin. The only remaining characteristic to assign to him is allergic to Sulfa. Given that, we now also know Mr Puggsworth must have been allergic to penicillin (as he was given as one of the two allergies). We now have:

1. Puggsworth, Penicillin (allergic to)
2. ?, ?
3. Irving, Beach
8. Dickens, Klacid
Easton = Sulfa (allergic to)

This is enough information to position all of the characteristics. Calcium, Drunk, Sulfa, Grapefruit, and Asthmatic all must appear in that given order, and the remaining three are placed already.

1 Puggsworth Penicillin

2 ? Calcium

3 Irving Beach

4 ? Drunk

5 Easton Sulfa

6 ? Grapefruit

7 ? Asthmatic

8 Dickens Klacid

Mr Irrgang is given as after Sulfa, and also not asthmatic, which only leaves grapefruit (must be a different Mr Irrgang to the puzzle author then: he doesn't like grapefruit!). From the same clue, Mr Richards is before Sulfa, and is also given as not drunk, so he must be taking Calcium supplements. We're also told both that Mr Nichols is not drunk and Mr Carlford is not asthmatic, so they must be the other way around. This gives the following final assignment of characteristics:

1 Puggsworth Penicillin

2 Richards Calcium

3 Irving Beach

4 Carlford Drunk

5 Easton Sulfa

6 Irrgang Grapefruit

7 Nichols Asthmatic

8 Dickens Klacid

A clue "PRICEIND" can be seen by reading down the first letters of the names, which helps us work out what to do later. Before we get there though, there are the drugs scattered around the puzzle. One idea of how to tie them in is to try and treat the odd conditions that people have, however this won't go very far. The right approach is clued by title of the puzzle, "interactions", which is a pharmacological term specifically referring to drugs which interact negatively and should not be taken together. The pharmacist has also been accused of "gross negligence", and seems a little confused. All this points towards pairing each of the drugs with the given characteristics in the worst way possible. Some web research can lead to the following discoveries:

Amoxil is a synthetic-penicillin-based antibiotic, which is not good if you're allergic to penicillin
Calcium supplements and antacids reduce the absorption of alendronate (Fosamax)
Cordarone-X can make your skin more sensitive to sunlight, so sunbaking is bad
Do not drink alcohol while you are taking Flagyl and for at least 2 days after you stop taking it
Bleph 10 is a sulfonamide based drug, which would trigger a Sulfa allergy
Grapefruit contains furanocoumarins which slow metabolism of simvastatin (Zocor), leading to a risk of toxicity
Beta-blockers such as Betaloc cause the airways to constrict increasing the risk of asthma attack
There is a potentially fatal interaction between clarithromycin (Klacid) and colchicine (Colgout)

This is not a trivial step. Other combinations do interact to some extent, but those listed above are what we believe to be the most compelling pairings. If in doubt, some trial and error with the next step can help to confirm the correct pairings. The full list of associations and the worst possible drugs from the list provided that they could be given is:

1 Puggsworth Penicillin Amoxil

2 Richards Calcium Fosamax

3 Irving Beach Cordarone-X

4 Carlford Drunk Flagyl

5 Easton Sulfa Bleph 10

6 Irrgang Grapefruit Zocor

7 Nichols Asthmatic Betaloc

8 Dickens Klacid Colgout

Speaking of the next step, the earlier "PRICEIND" message is a clue to index into the names of people by the price on the price tag of the drug they were given. Doing so gives the letters WARFARIN, which is a drug with many interactions. Although the puzzle design thus far may motivate a further step of finding something which interacts with warfarin, there are actually so many interactions that doing this would not lead to any clear choice. WARFARIN is the solution to the puzzle.