Anyone who has ever waded through the fine print on the package insert of a prescription drug knows that the list of potential side effects can be long and alarming—and difficult to understand.

Recent development: The FDA is updating the design used for prescription drug package inserts to make them easier to read. The redesigned package inserts are required for prescription drugs approved on or after June 30, 2006. For drugs approved in the five-year period prior to that date, the new format will be gradually phased in. Inserts for drugs older than that will be revised by manufacturers on a voluntary basis.

However, this good news does not change the fact that all drugs can cause side effects. Depending on the medication, there are literally hundreds of side effects that can occur, potentially affecting every organ system and bodily function.

Gastrointestinal side effects are among the most common. Dozens of drugs, including the antibiOtics ciprofloxacin (Cipro) and erythromycin (EMycin), commonly prescribed for urinary tract, respiratory and skin infections, can cause upset stomach, diarrhea and/or abdominal pain.

Other examples: The antibiotic amoxicillin Amoxit can cause nausea...digoxin (Lanoxin), a heart medication, can cause vomiting...narcotic pain medications can cause constipation.

Hives and/or rashes also are common side effects. These skin conditions, which often are the first sign of an allergic reaction to a medication, can occur with aspirin, antibiotics and atorvastatin Lipitor), a cholesterol-lowering drug.

Anaphylactic shock, a potentially fatal type of allergic reaction in which the breathing passages are constricted and blood pressure drops precipitously, may not occur the first time a drug is taken but rather after a third or fourth dose. Swelling (especially around the face and throat) and/or difficulty swallowing are red flags that you may be suffering from a serious allergic reaction.

Important: Each person responds differently to medication-side effects may occur in some people but not in others. It's crucial to understand the potential side effects of the medications you are taking so that you can report any adverse reactions to your doctor and/ or pharmacist.

Spend the 10 to 15 minutes it typically requires to carefully read the package insert. Use reading glasses or a magnifying glass, if necessary. Checking a drug reference book (preferably one with large print) also is helpful. When picking up a prescription, ask to speak to the pharmacist about potential side effects. And of course, discuss potential side effects with your doctor when medication is prescribed.

Once you're taking a prescription drug, it's not always easy to identify side effects, because they can mimic the condition that is being treated. Usually the only way to distinguish between the two possibilities is to stop taking the drugl—with your doctor's approval—to see if the side effects stop.

Side effects that are often missed by patients -and doctors…

Cognitive Problems

Prescription drugs that affect the central nervous system can impair thinking, memory, alertness and judgment. These include barbiturates, such as phenobarbital (Bellatal), prescribed for epilepsy or insomnia...anticholinergics, such as atropine (Sal-Tropine) and scopolamine (Scopace), prescribed to slow stomach motility (movement of food through the digestive system).. antispasmodics, such as propantheline (Pro-Banthine) and dicyclomine (Bentyl), for bowel spasms or cramping...muscle relaxants, such as chlorzoxazone (Paraflex) and carisoprodol (Soma), for muscle stiffness or back spasms...and antidepressants, such as paroxetine (Paxil) and fluoxetine (Prozac). Central nervous system stimulants, such as methylphenidate (Ritalin), also can affect cognition. Stimulant drugs are often used for attention deficit hyperactivity disorder (ADHD).

What you may not know: Certain blood pressure medications, such as methyldopa (Aldomet) and clonidine (Catapres), may affect heart rate and/or cardiac output (the pumping efficiency of the heart), which can lead to disorientation.

Cognitive symptoms to watch for: Cognitive changes, such as forgetting simple things that you normally remember, are worth noting. If family members and/or friends tell you that they see a change in your cognitive function, consult your doctor and/or pharmacist. Your doctor may be able to adjust the dosage, or it may help to take the drug at night. As an alternative, your doctor may prescribe an equally effective drug that won't trigger side effects in you.

Sexual Dysfunction

Antidepressants, including the widely prescribed selective serotonin reuptake inhibitors (SSRIS), such as fluoxetine (Prozac) and escitalopram (Lexapro), are known to cause sexual dysfunction, including changes in libido, inability to reach orgasm and/or difficulty achieving an erection. Diuretics, such as furosemide (Lasix) and hydrochlorothiazide, can lead to male impotence. Some drugs that are used to treat benign prostatic hypertrophy (a condition in which the prostate gland is enlarged), such as finasteride (Proscar) or dutasteride (Avodart), also can affect sexual functioning, as can antianxiety agents, including alprazolam (Xanax), lorazepam (Ativan) and diazepam (Valium).

What you may not know: Older types of drugs used to treat acid reflux and ulcers, including H2 antagonist drugs, such as cimetidine (Tagamet), block androgen receptors, which are necessary for male sex hormone activity. These drugs also can decrease testosterone synthesis, leading to impotence and breast enlargement in some men. Newer H2 antagonist drugs, such as famotidine (Pepcid) and nizatidine (Axid), and some of the proton pump inhibitors, including omeprazole (Prilosec) and esomeprazole (Nexium), don't have this effect.

Sexual dysfunction symptoms to watch for: Report any changes in sexual function, including inability to have or maintain an erection, change in libido and inability to reach orgasm, to your doctor and/or pharmacist as soon as possible. Your doctor may adjust the drug dosage, prescribe an alternative medication in the same class or suggest alternative dosing schedules, such as taking the drug in the early morning.

Weight Gain

Some newer drugs, including the antipsychotic agents olanzapine (Zyprexa) and quetiapine (Seroquel), which are used to treat severe mental disorders, such as schizophrenia, may cause weight gain. The antidepressant bupropion (Wellbutrin), which is often used instead of an SSRI because it typically does not cause sexual side effects, also can trigger weight gain.

What you may not know: Some diabetes drugs, such as glyburide (DiaBeta) and chlorpropamide (Diabinese), can lead to weight gain.

Weight gain symptoms to watch for: If you gain more than five pounds in any four-to six-week period that you are taking a drug, speak to your pharmacist and/or doctor. Consider weighing yourself daily if you are prescribed a drug that can cause weight gain. Meanwhile, try reducing daily calories and/or exercising more to control any weight gain.

Best Ways to Avoid Side Effects

To help guard against potentially dangerous side effects, follow these steps when your doctor prescribes medication…

  • Review the dosage. Drug dosages are usually determined by studies based on young, healthy volunteers or patients with uncomplicated diseases. People who have less body mass (under 120 pounds) don't need the same dose as someone who tops 200 pounds.

What to do: Ask your doctor if he/she is prescribing the lowest possible dose for a person your weight.

  • Mention your age. As we age, our kidneys and liver are less efficient at metabolizing drugs.

What to do: Ask your doctor whether he is prescribing the lowest possible dose for a person your age

Nicotine Drugs to Quit Smoking

Smokers who use nicotine-replacement medications are twice as likely to kick the habit as people who try to quit cold turkey. These medications deliver small, steady doses of nicotine to ease withdrawal symptoms without the toxic substances contained in cigarettes. Always consult your physician before trying a nicotine-replacement drug.

Over-the-counter and prescription options available…

  • Nicotine patch. People who smoke a pack or more a day should start with the patch, a full-strength replacement medication. Available over-the-counter and by prescription.

Nicotine gum should be chewed and held in the mouth for about 30 minutes every hour or two. Not for people with dentures. Over-the-counter only.

  • Nicotine inhaler. Good for smokers who like the hand-to-mouth feeling. People trying to quit smoking can take a puff of the inhaler several hundred times a day. Prescription only.
  • Nicotine lozenges. Less conspicuous to use than gum, inhalers or spray, lozenges last 20 to 30 minutes. People can use up to 20 a day. Over-the-counter only.
  • Nicotine nasal spray. This product can be used once or twice an hour. Not for people with asthma. Prescription only.

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