If you read an aquarium web site, magazine, or book you'll likely come across recommendations of products for treating disease. The problem is that not all brands and not all drugs are equally available throughout the world. Since we're a very international crew, a moment spent looking over the table below should help clear up any confusion you have about the treatment we've recommended. 
 

Antibiotics 

In most countries access to antibiotic medications is restricted to some degree. A notable exception is the United States, where a variety of antibiotics can be obtained from tropical fish shops. In other countries, you will either need to use antibacterial alternatives or ask a veterinarian to supply you with the required antibiotics (generally at low cost, but it's admittedly a hassle). 

Examples of antibiotics sold in the United States you won't find in tropical fish stores in most other places include:

        API Furan-2 (Furan compounds)

        API Erythromycin (Erythromycin)

        API T.C. (Tetracycline)

        Mardel Maracyn-Two (Minocycline)

        Seachem Metronidazole (Metronidazole)

Antibacterials 

In states where sale of antibiotic treatments is restricted, aquarists often turn to antibacterial medications. Whilst these can be effective, the claims made by the manufacturers as to their efficacy have to be taken in context. Often they depend upon early diagnosis and immediate treatment. Do not expect an antibacterial medication to have much impact on an advanced case of dropsy or severe hole in the head. Since many of the problems that antibacterials and antibiotics are used to treat are typically caused by lack of quarantining, careless use of live food, or poor water quality management, this underlines the fact that prevention is definitely better than cure. In other words, the best way to deal with dropsy or hole in the head is simply not allow it to become a problem in the first place.
 

Warnings!

        Most medications are not safe to use with invertebrates (such as shrimps).

        Most medications are not safe with sensitive fish, including clown loaches, certain catfish, mormyrids, pufferfish, stingrays, and sturgeons.

        Most medications are not safe used in combination with other medications.

        Almost all medications will only work when carbon has been removed from the filter.

        Some medications will not work in soft/acid water (e.g., JBL Gyrodactol).

        Some medications require the addition of salt to be effective (e.g., Interpet #13 Swimbladder Treatment).

What's available 

The following table lists some of the popular freshwater aquarium medications. Inclusion on this table isn't an endorsement though, and you may find that some products are more effective than others. As ever, research and talking to experienced aquarists are the keys to make wise decisions. This list isn't exclusive either, and there will be numerous other brands available at your retailer performing equivalent functions. 

Major manufacturers 

Some brands are sold worldwide, but others are only sold in certain areas. The following gives a listing of the featured manufacturers and their approximate area of distribution at the time of writing (July 2007).

Aquarium Pharmaceuticals

Based in the US

Available in North America and parts of Europe

http://www.aquariumpharm.com

Aquarium Products

Based in the US

Available in North America

http://www.aq-products.com

eSHa Labs

Based in the Netherlands

Available in UK and Europe

http://www.eshalabs.com

Hikari USA

Based in the US

Equivalent Hikari products available worldwide

http://www.hikariusa.com

Interpet

Based in the UK

Available in UK and Europe

http://www.interpet.co.uk

JBL

Based in Germany

Available in UK and Europe

http://www.jbl.de

Kusuri

Based in the UK

Available in UK and Europe

http://www.kusuri.co.uk

Seachem

Based in the US

Available worldwide

http://www.seachem.com

Waterlife

Based in the UK

Available in UK, Europe, South Africa, Australia, Asia, Middle East, etc.

http://www.waterlife.co.uk