Faced with a shop shelf stuffed with medicines, most of us will reach for a brand we recognise. This is probably because we think we can trust a household name not to kill us. Certain brands are associated with feelings of comfort, safety and effectiveness; it is easy to assume that because we have heard of it, it must be the best.

Even if you want a cheaper alternative, it can be hard to identify the unbranded “generic” medicines that lurk at the back of the shelf with unassuming packaging and unrecognisable names. This, of course, is no accident. “The big pharmaceutical companies have the resources to push their products,” says Brendan Nyss, spokesman for the Royal Pharmaceutical Society (RPS) and a community pharmacist at Le Quesnes Pharmacy in Jersey, “and the large retail chains promote these brands because they make more money out of them.”

How a pharmacy displays over-the-counter medications can be more about money than quality. “The powerful drugs companies sometimes offer retail outlets promotional prices in return for shelf space,” explains Nyss. “They may offer goods at a ‘bonus’ price in return for a display unit on the counter for a certain number of weeks, and they also run very good training courses [for pharmacists] about their product, in order to keep the brand at the forefront of people’s minds.”

So are the big names really better, or will cheaper, unbranded drugs do the job just as well? Here is a look at how Britain’s top-selling non-prescription remedies compare with their cheaper equivalents.

Nurofen

According to the RPS, the painkiller Nurofen was Britain’s bestselling over-the-counter drug in 2007. There are many different Nurofen products but in all of them the main active ingredient is ibuprofen. While Nurofen retails at £2.89 for a pack of 24 tablets each containing 200mg of ibuprofen, Cuprofen, made by Seton Healthcare, offers a pack of 24 tablets each containing the same 200mg of ibuprofen for only £1.10. “If you choose the Nurofen,” says Nyss, “you are simply paying for the box.”

But is it worth paying more for the additional benefits some Nurofen products offer? Nurofen Express, for instance, offers 400mg of ibuprofen – a prescription dosage – in a special “twice as fast” liquid capsule form (£3.82 for 10 capsules). “A liquid capsule probably wouldn’t speed up the process much at all,” says Nyss. “In fact, ibuprofen works very quickly as it is – on average it takes about 15 minutes to be absorbed by the body.” A pack of 24 Cuprofen tablets containing the same 400mg of ibuprofen costs only £1.95.

Nurofen Tension Headache comes in “caplet” form, but what makes it specifically effective for treating tension headaches? “They offer exactly the same ibuprofen dosage [as regular Nurofen] – 200mg,” says Nyss. The only difference is that these pills are oval-shaped and contain something called lysine. “Lysine is a different base that supposedly makes it easier for your body to absorb the ibuprofen,” says Nyss.

Nurofen Plus does, however, seem relatively unusual, offering a combination of ibubrofen (200mg) and codeine (12.8mg). “I don’t know of any generic equivalents to this,” admits Nyss. “But really, 400mg of generic ibuprofen will work just as well.”

Lemsip

Designed to relieve the symptoms of colds and flu, most Lemsip products offer a combination of a nasal decongestant called phenylephrine and the painkiller paracetamol. Some products also contain guaifenesin, an expectorant, which can help thin the mucus in your chest. “Lemsip offers lots of fancy flavours,” says Nyss, “and choice, such as granules that dissolve directly on the tongue or a ‘max strength’ version containing more paracetamol.” However, he says, “You can get exactly the same drugs about 50% cheaper in generic form.”

A packet of five Lemsip Max sachets containing 1,000mg paracetamol and a decongestant costs £2.50. A packet of five sachets containing equivalent doses of the same drugs, supplied by AAH, a wholesaler, costs £1.80. “There may be tiny variations in the content,” says Nyss, “but the generic brands are just as effective as Lemsip in treating these symptoms.”

Gaviscon

This antacid medicine for heartburn and indigestion comes in pill, liquid or sachet form, in flavours such as peppermint, lemon or aniseed. Gaviscon contains “alginate”, a derivative of seaweed, which, explains Nyss, “acts as a kind of raft that sits on the acid in the stomach, suppressing acid reflux”. Alginate itself is specific to Gaviscon. The manufacturer of Gaviscon, Reckitt Benckiser, is currently in litigation to protect its patent. But again, there are cheaper alternatives. Peptac is an alginate derivative very similar to Gaviscon. It comes in peppermint or “original” liquid form, though not in tablets, and, says Nyss,”is very effective”.

Gaviscon does offer an “advance” formula containing double the alginate. Peptac does not have an equivalent. However, says Nyss, “I would always recommend shopping around for a generic version to start with, then moving up to something stronger if that is not effective.” Since Gaviscon costs £7.95 for 600ml while Peptac is just £3.50 for a 500ml bottle, this approach could soothe your bank account too.

Calpol

Calpol is the bestselling baby and child pain and fever treatment. A 5ml teaspoon contains 120mg of paracetamol and a 200ml bottle (for children aged three months to six years) costs £3.90. You could, however, buy exactly the same amount of paracetamol for your baby for just over a third of the price if you are prepared to forgo the familiar packaging. A 200ml bottle of Enterprise Own Brand, containing the same 120mg dosage of paracetamol per 5ml, costs only £1.40.

There are, of course, a whole range of Calpol products to tempt you. Calpol Night, for instance, contains 12.5mg of a sedating antihistamine called diphenhydramine hydrochloride (£3.06 for 100ml). But even this comes in much cheaper forms: Medised contains the same dosages of exactly the same drugs, but is £2 cheaper (£4.33 for 200ml).

“The medication is exactly the same, and the generic brands are also sugar-free, with various flavours,” says Nyss. “There’s no meaningful difference – except for the marketing.”

Hayfever remedies

These are not bestsellers, but at this time of year countless allergy sufferers will be searching the aisles for drugs such as Piriton, which contains chlorphenamine, Clarityn, which contains loratadine, and Zirtek, which contains cetirizine. All three drugs are effective antihisthamines. So what do you buy?

Piriton is £3.15 for 30 tablets each containing 4mg of chlorphenamine – though this drug can make you drowsy. Buy the same quantity of the same drug in generic packaging – often sold under no brand at all – and you’ll pay just £1.99. Clarityn, a non-drowsy alternative, containing 10mg of loratadine, costs £7.50 for 30 tablets. It could, however, come much cheaper if you buy the generic form of loratadine at just £3.95 for 30 tablets

Zirtek, meanwhile, retails at an eye-watering £13.90 for 30 tablets containing 10mg cetirizine per tablet. But buy your cetirizine in generic form and you’ll hand over only £2.99 for 30 tablets. It pays to shop around, says Nyss. Boots and Superdrug own brands of cetirizine, for example, are a little more expensive than the generics, although are often on special offer.

“You can stand in front of people and tell them the cheaper one works just as well,” says Nyss, “but they’ll still believe a TV advert before they’ll believe a pharmacist with a degree”.