Saudi arabia,yanbu.
I'm not in the uk.
OK!
Baytril is the antibiotic that is licensed for guinea pigs. Doxycycline is also safe to give for respiratory infections.
Guinea Lynx :: Medications
Please make sure that you also give a pinch of probiotics either an hour before (US recommendation) or 1-2 hours after the antibiotic (UK recommendation), either works equally well. This is in order to protect the gut bacteria that are vital for the digestion.
Probiotics, Recovery Foods And Vitamin C: Overview With Product Links
Please make sure that any air conditioning (I imagine that you have one?) is not directly aimed at your guinea pig cage; this can cause respiratory infections. Guinea pigs are not equipped for a desert climate like in the US Southwest or in your country; they often suffer from recurring/permanent breathing problems in these situations (whether they are infectious or not is impossible to say without a vet exmination).
Any air conditioning will additionally dry the air. Try and see whether a bowl of steaming water next to the cage will ease the breathing.
The respiratory tract in guinea pigs is very small and narrow. They can also not breathe through their mouth. The noise your guinea pig is making is in my experience typical for an infection in the upper respiratory tract (throat/bronchia). You can in a pinch check roughly by holding your ear next to the head/nose, the neck (throat/bronchia) or chest (lungs) of your guinea pig to try and figure out where the rough breathing is coming from.
It would help both parties a lot if you please added your country to location in your account details (accessed by clicking on your username on the top bar). This makes it appear with every post you make and allows us to tailor any advice to what is relevant and available where you are straight away.
We have members and enquiries from all over the world but as long as not stated otherwise our default is UK based, which has got much stricter laws re. medications, often different medical brand names, not to mention widely available vet access. It also means that we can take the climate and climate related problems into account.