Prescription Drug Side Effects

You might be surprised at what can raise or lower drug levels in your body.
by Virginia Hopkins

When drugs are in the research and testing phase, they are most often given to adult men between the ages of 25 and 50, but drugs may act and interact very differently in children, teenagers, women, pregnant and nursing women, menopausal women, and particularly in the elderly, where nutrient absorption and liver function are issues. Your physician's only way of gauging your tolerance to a drug is to begin with a standard dose for an adult male and see what happens. If you don't complain of side effects or no effect, chances are the dose will never be changed.

There are dozens and dozens of factors that can influence what effect a drug has on you, from how much sleep you got last night and what you had for breakfast, to the condition of your liver and your blood pressure. For example, alcohol abuse can greatly increase or decrease tolerance to a drug, as can obesity, exercise, stress levels and exposure to pollutants such as car exhaust, pesticides or industrial chemicals.

Drugs and nutrients can affect each other in your digestive system, in your bloodstream, in your liver and kidneys, or at the cell level where the drug or nutrient receptor is.

Just as it takes a variety of vitamins, minerals, amino acids and enzymes to process food so that your cells can use it, drugs also go through changes as the body uses them. They are changed as they are made useful, as they are being used, and as they are being excreted from the body. Any interference in this process caused by nutritional deficiencies or interference from other drugs, food or alcohol, can raise or lower drug levels.

Your Body's Drug Disposal Systems
The four major routes for excreting a drug from the body are the kidneys, liver, skin and lungs. Most drugs are processed out through the liver and then the kidneys. If you have kidney or liver disease, how your body handles drugs is profoundly affected. Food, drink or lifestyle habits that stress and damage your kidneys or liver, such as alcohol abuse or chronic exposure to toxins such as solvents and paint fumes, can also affect how you process drugs. Kidney or liver stress or damage usually raises drug levels higher than normal by slowing down the excretion process.

The aminoglycoside antibiotics such as streptomycin, kanamycin, gentamicin and garamicin cause kidney damage in as much as 15 percent of patients treated with them, but thousands of other drugs cause less obvious stress on your kidneys. When your drug information insert indicates “renal” (kidney) problems, you should be aware that the drug is probably going to be hard on your kidneys.

Keeping Your P-450 Pathways Clear
Many types of drugs are prepared for clearance out of the body through the liver using the cytochrome P-450 enzymes, also known as the cytochrome P-450 pathways.

In a drug-free body, or in the presence of only one drug, the P-450 pathways can handle the load. When you have more than one drug cleared through the same pathway, the system quickly gets overloaded, stalling the removal of the drugs from the system. The result is an overdose that can be life-threatening.

Some examples of drugs that either use the P-450 pathways or block its action are the SSRI antidepressants (e.g. Prozac, Zoloft), cimetidine (Tagamet), cisapride (Propulsid), the cholesterol-lowering drugs in the statin family, the macrolide antibiotics such as erythromycin and clarithromycin, most antifungal drugs such as ketoconazole and miconazole, antiarrhythmic drugs such as disopyramide (Norpace), the seizure drug phenytoin (Dilantin), the anti-Parkinson's drug bromocriptine (Parlodel), the benzodiazepine anti-anxiety drugs such as diazepam (Valium) and nefazodone (Serzone), the calcium channel blockers such as nifedipine (Procardia), the theophyllines used to treat asthma, the tricyclic antidepressants such as Elavil, the blood thinner warfarin (Coumadin), tacrine (Cognex) used to treat Alzheimer's, the antihistamines terfenadine (Seldane) and astemizole (Hismanal) and caffeine.

And these are just the most commonly used drugs. Grapefruit juice also uses this pathway, which is why drinking it is contraindicated with some drugs.

How many people do you suppose have been killed in a scenario similar to this one: Joe is taking a calcium channel blocker long-term, is temporarily put on a macrolide antibiotic to treat chronic bronchitis, then has a glass of grapefruit juice and a cup of coffee with breakfast, raising his levels of the calcium channel blocker so high that his blood pressure drops precipitously, causing heart failure. It's not an unlikely scenario. Or let's say it's in the evening and he takes some Tagamet (which is available over-the-counter) for heartburn and a Valium to help him sleep.

Your best bet is to check with your pharmacist before mixing any drugs, even over-the-counter drugs. Labels that warn of such things as hepatic (liver) toxicity, injury, dysfunction or function impairment, which is medical-ese for liver poison, should flash a red light in your head.

Take Care of the Liver When On Drugs
Your liver is one of the busiest organs of the body, working constantly to process food for transport through the bloodstream and to metabolize waste matter for excretion through urine or feces. The list of prescription drugs that stress or damage the liver is probably longer than those that don't. If you drink alcohol in excess and take liver-stressing drugs, you could be doing substantial damage to your liver.

Some symptoms of liver toxicity are swelling and redness in the palms of the hands, yellowish skin and whites of eyes, itching, small benign fatty tumors and reddish spots on the skin or lumps under the skin of damaged blood vessels.

Use Caution with Acetaminophen
One of the most commonly used drugs that damages the liver is acetaminophen (Tylenol), which is loudly touted in advertising for pain relief because it doesn't upset the stomach the way aspirin or ibuprofen do. What those ads neglect to tell you is that acetaminophen is very hard on the liver.

Recent research has shown that acetaminophen may inflict most of its damage on the liver by blocking the production of the important antioxidant glutathione. Without glutathione, the liver's ability to break down toxins for elimination is impaired. According to a study published in the journal, Free Radical Biology & Medicine, one hour after an injection of acetaminophen, glutathione levels decrease as much as 83 percent! That is a vulnerable liver. If some type of stress is placed on the liver (i.e. alcohol, pesticides) at the same time the acetaminophen hits it, the damage could be considerable.

If you’re in pain you may be in the position of having to pick your poisons, so here’s a health-protecting strategy: if you’re going to take acetaminophen, take the liver-protective herb milk thistle beforehand (follow directions on the bottle) and add 500 mg of the amino acid cysteine to your daily vitamins. Cysteine is the precursor to glutathione. Also be sure to avoid alcohol when you're taking acetaminophen.

Because drugs have potent and specific actions, they can easily become toxic in excess. One of the biggest reasons that natural remedies are preferable to use over prescription drugs whenever possible is that the natural remedies tend to be much gentler and safer if you take too much.

Factors that Can Increase or Decrease Drug Levels

  • Sex
  • Age
  • Race
  • Overweight or underweight
  • Pregnancy and Nursing
  • Illness
  • Alcohol abuse
  • Food
  • Other Drugs
  • Digestion
  • Kidney or liver damage
  • Nutritional deficiencies
  • Supplements
  • Exposure to toxins such as paint fumes, solvents, pesticides
  • Over- or under-exercise
  • Stress
  • Time of day

Drugs That Metabolize Differently in Women
There are probably many more drugs than these that are metabolized differently in women, but these are the ones we currently know about. If you're given a drug and experience negative side effects, ask your physician to try changing the dosage.

  • alcohol
  • amitriptyline
  • benzodiazepines
  • beta blockers
  • chlordiazepoxide
  • diflunisal
  • imipramine
  • oxazepam
  • methylprednisolone
  • piroxicam
  • prednisolone
  • trazadone

Common Drugs that can Decrease the Effect of Oral Contraceptives
If you're taking oral contraceptives and are prescribed one of these drugs, be sure to use an alternative form of birth control during the time you're taking these drugs and for at least two weeks afterwards.

  • antibiotics
  • anticonvulsants
  • azole antifungals
  • griseofulvin
  • ritonavir
  • rifampin


For more information about how a specific drug may affect you, please read Prescription Alternatives.

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