It's an expense we often take in stride - and one that tends to hit our wallets harder during the winter months. 

Research shows the average Briton spends more than £100 each year on non-prescription medicines such as cough syrup and paracetamol. 

But financial experts say we could be more than halving our annual medicine expenditure - simply by following one simple trick. 

They claim drug companies spend millions promoting 'only-use-the-name-you-know' messages - persuading customers to chose their drug above all others. 

It's messaging that appears particularly effective on Gen Zers. 

A consumer research survey found that 78 per cent of the group, now aged between 13 and 28, trusted brand name medications more than generic ones. 

Yet you can often save big by buying an identical pill, just in different packaging. 

In fact, some are half the price of their doppelgangers. 

How to spot a bargain

Your top name-brand pharmacy drug could contain the exact same pill as the generic drug beside it - just for double the price. 

To figure out whether you could get a steal by swapping to a cheaper, unbranded alternative, check out the PL number on each box. 

A medication is given a PL number by the Medicines and Healthcare products Regulatory Agency (MHRA) when it is licensed to be marketed in the UK. 

Though licensing the product, however, the MHRA does not control the prices these medications are sold at.

Typically on the bottom or side of the medicine packaging, the PL number will say PL and then a collection of digits. 

And while medicines are sometimes put in different packaging, and under different brand names, if it's the same PL number, it's the exact same drug. 

A Daily Mail investigation found a number of popular medications being sold for a variety of prices - despite containing the same drug - on the websites of high street stores. 

Here's what to swap to save this winter season: 

Cold and flu relief  

Feel yourself coming down with a sniffly nose and headache? 

You may want to reach for some of the biggest names in flu medication - Sudafed, Lemsip, Nurofen.

But, despite claims made on the box, not all drugs justify their price tag... 

For example, Sudafed Congestion & Headache Relief Day & Night Capsules are £6.60 at Boots.

But Boots' own-brand Max Strength Cold & Flu Relief Day & Night Capsules are £2.65.

And Savers, meanwhile, sells Galpharm Max Cold & Flu Day & Night Capsules for just 99p. 

All three have an identical PL number: 12063/0073.

Buying the generic, unbranded drug will save you £5.  

Sinus pain   

It's another common winter ailment. 

Sinus pain, commonly caused by infections like a cold or flu, which can cause swelling and pressure in the sinuses, can be painful and irritating. 

But don't just grab for the first remedy on the shelf. 

Sudafed Sinus Max Strength Capsules are £5.49 at Holland & Barrett and £5.80 at Boots.

But Boots' own-brand Max Strength Sinus Pressure & Pain Relief Capsules have the same PL number - 12063/0067 - and are just £2.65. 

Headache relief  

If simple paracetamol or ibuprofen doesn't suffice for a headache, there are still less expensive options available than name-brand targeted drugs.  

Period pain reliever Feminax Express is currently on sale for £4.89 at Savers, and £5.40 at Boots for 16 tablets.

Yet Boots's Rapid Ibuprofen Lysine tablets, meanwhile, have the same PL number - 12063/0071 - and cost just £4.40 for 16 tablets.

But the best deal for the same drug is the Boots Migraine Pain Relief, which is on sale for just £2.89 for 12 tablets.

While you get fewer of them, it's still 20 per cent cheaper per tablet. 

Sleeping aids

Having trouble nodding off at night, but don't want to spend a fortune on sleeping pills? Don't fret. 

Nytol's One-A-Night tablets cost an eye-watering £9.90 at Boots for 20 doses of the 50mg pill. 

But Boots' Sleepeaze drug - which shares the same PL code, 02855/0071 - costs £7.50 for the same amount of medication, saving you £2.40. 

The same goes for the 25mg version of the sleeping drug. Both medications have the PL code 02855/0070.

But whilst Nytol's Original 25mg caplets are on sale at Boots for £7.25 for 20 pills, the Boots 25mg edition of Sleepeaze is just £5.40. 

Take your pick.