Drugs for colds and flu, what do they do and which should you buy?

After finally recovering from a three week cold, I wanted to write a blog about a personal bugbear of mine. It's something I get so grouchy about (especially during a cold)  that even my most patient friends have stopped listening. Why is it that we end up paying through the nose for expensive cold and flu drugs, when there are exactly the same products on the shelves without a label? It was totally baffling to me, until a friend from a non medical background explained that, since she didn't know what the drugs did or what amounts she could take, she just bought the one in the best looking packaging. My campaign to inform people started there! I think it is important that we should know what we're taking, and what is appropriate for which condition, so here are the six active ingredients you will come across, what they do, and when you should take each.

1) Paracetamol

This classic pain killer is found in the vast majority of cold and flu products. Paracetamol is a very effective drug, it can help bring down a fever, and reduce the pain associated with a blocked nose. The standard adult dose is 1000mg every four hours. Paracetamol is processed by the liver, and too much can cause liver damage. It is therefore really important not to accidentally overdose by taking more than one product containing  paracetamol, just check on the box if you're not sure. 

2) Phenylephrine

The viruses that cause colds love to replicate in the cooler, more alkaline environment found in the cells of the upper respiratory tract. The immune system then has to eliminate the virus from these areas. Inflammation is the immune systems way to deliver immune cells to a site of infection. Firstly there is increased blood flow (making inflamed areas look pink),  then small blood vessels in the nose become ‘leaky’, allowing the cells - along with a lot of fluid- to escape into the virus infected tissue. This build up of fluid leads to the horrible bunged up feeling, and to a very runny nose! Most flu and cold remedies contain phenylephrine. This drug works by causing the blood vessels in the nose to constrict, to prevent this fluid from leaking out. The maximum dose is 12mg every four hours. 

3) Guaiphenasin

Guaiphenasin is useful if your cold also has an accompanying chesty cough. If your cough is dry an irritable, this drug won't help much - although it won't do any harm. It is often included in the "all in one" cold, flu and cough medications and works by making the secretions in your chest more runny, allowing them to be cleared more easily. 

4) Ibuprofen

Ibuprofen works by interfering with pro-inflammatory pathways to reduce the production of inflammatory mediators and signals. It can safely be taken with paracetamol and, to get the maximum possible benefit, I take them spaced apart by two hours. That way you always have one drug working in your system at any time. There is some unverified research from Southampton University that suggests that ibuprofen might actually make you take slightly longer to recover from a cold/cough, but to me the benefits far outweigh this! 

5) Drugs to wake you up, or help you sleep

Loads of "all in one" cold remedies contain a dose of caffeine. It works by stimulating the central nervous system to make you feel more alert, which can be a life saver when you are feeling lethargic and tired. Some brands of "all in one" cold and flu drugs advertise different pills for day and night, the only difference is that the night time dose has no caffeine. Drugs marketed for colds and flu do not often drugs to make you sleep.

There is however the option to buy remedies that contain promethazine and dextrometorphan - both of which are mild sedatives in addition to their other effects. Promethazine is an old antihistamine that is still used for its "drowsy" side effects, and dextrometorphan is a distant cousin of morphine that can be used to suppress coughs and aid sleep. Dextrometorphan is found mainly in cough syrups, but is also found in Night Nurse cold and flu drugs.

6) Xylometazoline

This drug is only found in nasal sprays but works in the same way as phenylephrine. It is, however, quite potent and should only be used for a short time because it can damage your nose if used for more than a few days.

Various combinations of these six drugs are available as multiple brands, with wildly varying costs, but if you want the best cold and flu drugs out there all you really need to do is look at the back of the box and find the cheapest one that contains 500mg paracetamol, 6.1mg phenylephrine and 25mg caffeine per tablet. Ibuprofen is the same whether it is branded or not! If you want to help a chesty cough then something with guaiphenasine, or calm an irritable one then choose something with dextrometorphan. 

Good luck, hope you feel better soon!