Howdy dazle:
It's a good question, but not as simple as you might think. Actifed and Sudafed are brand names for various cold and sinus medications. When an over-the-counter (OTC) drug manufacturer has a popular brand name, they have a tendency to tack it on to multiple different products- and they can vary by country. You need to read the label on each product to know what's in it.
In the USA, Warner-Lambert markets at least 2 kinds of "Actifed". One has pseudoephedrine (a sympathomimetic amine decongestant in the adrenaline family) with triprolidine (an antihistamine that can be sedating). The other combines pseudoephedrine with chlorpheniramine (another antihistamine that can be sedating). They market at least 14 different kinds of "Sudafed", I believe all with pseudoephedrine, but some mixed with cough medicine, antihistamines, acetaminophen, expectorants, etc. It could very well be different in the UK. Read the label so you can be sure to get only the medications you want/need.
The active ingredient in these OTC meds that most interests divers is the pseudoephedrine. Pseudoephedrine is a decongestant that "shrinks" the tissues lining the nose, sinuses, eustachian tubes, etc. to help with equalization. A search of the board for "pseudoephedrine" will give you a wealth of information on its use and pros and cons. It has been discussed many times.
DAN has an article on pseudoephedrine and enriched-air diving at:
http://www.diversalertnetwork.org/medical/articles/article.asp?articleid=51
that addresses your partial pressure question. Be sure and catch the "What's the bottom line?" paragraph toward the end of the article. A search for "pseudoephedrine" on the DAN site will get you some more information too.
HTH,
Bill
