Prescription drugs are required by the FDA (or equivalent organizations in other countries) to have a officially-approved document describing the drug, which is usually called the "label." It's also called the USPI (United States product insert) in the US, and the SmPC or SPC (summary of product characteristics) in Europe. These documents are developed by the manufacturer, and scrutinized and approved by the regulatory agency, frequently after lots of discussions and give-and-take -- the manufacturer wants to present the information in the most positive light possible, and the regulators want the information to be absolutely accurate.
If you are considering starting a new drug, you might want to look at the USPI or SPC yourself. They are loaded with technical information, and includes the following:
description of the drug
indications (uses for the drug). It must be pointed out that these are the approved indications; many drugs are used "off-label" for medical conditions that are not officially approved. For instance, metformin has been used in pre-diabetes and in PCOS, as well as for the approved indication of type 2 diabetes.
contraindications (who should not take the drug)
adverse events (side effects)
drug abuse and dependence
dosage and administration
use in pregnancy, use in nursing mothers
use in children and older patients
how the drug is supplied
safety information for the patient
and also the date of the document's approval
(This listing is modified from the one at the FDA website.)
USPI documents may exist in either of two formats. The older one starts with a description of the drug, and is structured with sections following one after another after another; stuff you might be interested in (such as dosage and administration) may be buried way back in the document, and will be hard to find unless you can use your computer's "search" feature, as there's no table of contents. The newer format starts with a fairly short "Highlights of Prescribing Information" then has comprehensive "Full prescribing information" starting with a standardized table of contents -- and each section is numbered.
Where can you find a copy of the current label? It may be part of the packaging when you purchase the drug itself, but the information is also available elsewhere.
In the distant past (pre-Internet), the usual way to find labeling information was in a big book called the "PDR" (Physician's Desk Reference) that's updated annually. Most physician offices and libraries should have copies, and it's now on the Internet at http://www.pdr.net, but access is restricted to health care professionals who have appropriate code numbers to enter when registering. Anyway, the PDR in paper version is incomplete, not providing labels for many older or generic drugs, and the current labels for many drugs can be found elsewhere on-line.
The first place to look would be the manufacturer's website for the product, if they have one. Many best-selling medications (such as Lantus) can be found at websites with the product's name (such as www.lantus.com). Then it's a matter of looking around for a hyperlink to "prescribing information" or to a section named something such as "Healthcare Professionals" and clicking there.
If you click through to a Healthcare Professionals webpage, you may get a warning box that the information is only for Healthcare Professionals, but that won't stop the curious reader from continuing Once you're at the Healthcare Professionals area, it's again a matter of hunting, this time for "Prescribing Information." Clicking here will usually display the USPI, either in standard website formatting or in a PDF.
There may be additional steps needed. For instance, if the company is based outside the US, you may have to hunt for the US website then follow the steps I describe above. Or the company may not have a website for older products, and typing in a name of an older drug can come up with anything: the manufacturer's website, or an independent company that purchased the domain name, or nothing at all.
The most reliable alternate place to look for labels for US drugs is at the FDA's website, Drugs@FDA (http://www.accessdata.fda.gov/scripts/cder/drugsatfda/). It's comprehensive, but sadly, for some old drugs, searching for information comes up with a blank. For instance, I tried searching for chloromycetin, and there's lots of information about who made it, but the drug is consistently described as "discontinued." To get information on chloro, I ran a Google search, and found the information at Drugs.com.
If you're looking for labels for drugs that are not approved in the United States, and that you know are approved somewhere else, you may be able to find the information at other websites. For instance, for drugs approved in the UK, go to the eMC (The electronic Medicines Compendium) at http://emc.medicines.org.uk/ The eMC, like the FDA website, is free to use and unlike the PDR, you don't have to be a physician, nor do you need to register any personal details.
Drugs approved in Europe by the EMEA (European Medicines Agency) are found by starting from "EPARs for authorised medicinal products for human use"
http://www.ema.europa.eu/htms/human/epar/a.htm and finding the drug.
New Zealand approved drugs are at
And South Africa drugs are at
Why should a non-physician read the label? Well, obviously, you can wow your doctor at the next visit with all sorts of trivia you've learned. Or have some intelligent discussion about possible side effects that you've had. Or maybe by comparing two or more drugs in the same class, you can make an argument to switch from one to the other. And if you're concerned or confused by something your physician said (or didn't say), the label is the definitive source for information (with the exception that off-label uses for the drug are not described in the label). After all, you're the one who's taking the medication, and you have the opportunity to learn more. Go for it!