While most drugs have a pretty good margin of safety on dose, some can be quite hazardous if you take too much. The classic case (until it was finally withdrawn) was the hay fever drug called Hismanal, which could cause cardiac arrest with as little as one extra pill!

When the toxic or hazardous dose is quite close to the recommended dose, special vigilance is needed. Officially these are called" narrow therapeutic index" or NTI drugs

Here are several ways you can get in trouble with these drugs:

• Hoping for more benefit, you increase the dose.
• You get sick or have another health problem that reduces your body's ability to process this drug.
• It's a once-a-day drug and you try for an extra effect at night.
• Another drug interacts and increases the effect. (see this item!)

So what drugs should you worry about? Here are some examples of popular and widely prescribed drugs with a small margin of safety on dose.

• Coumadin is a drug to prevent blood clots and requires constantvigilancee in its use to prevent bleeding. In addition, it interacts with more than 60 other drugs, which can also effect the dose.
• Drugs for adult-onset diabetes can lower your blood sugar too much, causingdizzinesss or a blackout. For these drugs, it is not just the dose. Blood sugar also depends on how much sugar andcarbohydratess you have eaten recently.
• Asthma drugs present varying problems. Some drugs--for example, theophylline--cause problems when too much is used during an asthma attack. The other problem is that people try to get relief during an attack by taking one of the once-a-day systemic drugs such as Serevent. Don't do this!
• The popular heart drug called Lanoxin (or digoxin) can cause irregular or erratic heartbeat. And like Coumadin it interact with many drugs.

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