Some things you should know about prescription drugs.
Two or more drugs, taken atthe same time, can interactand affect the way one or theother behaves in the body. Forexample, an antacid willcause a blood-thinning (anti-coagulant)drug to be absorbedto slowly, while aspiringreatly increases theblood-thinning effect ofsuch drugs.
Two drugs with the sameeffect when taken togethercan sometimes have an impactgreater than would beexpected. This is calledpotentiation. Potentiationcan be helpful, as when theantibiotic trimethoprim isused to boost the effect ofanother antibiotic, sulfamethoxazole,in combattingcertain infections.
Potentiation also can bedangerous, particularly whenseveral central nervous systemdepressing drugs are involved. Evennon-prescriptiondrugs, such as antihistaminesthat are often used tofight colds, can increase thesedative effects of anesthetics,barbiturates, tranquilizersand some pain-killers.
Some drugs can cause sideeffects (adverse reactions). Usuallythese are mild--aslight rash, mild headache,nausea or drowsiness; sometimesthey are severe--prolongedvomiting, bleeding,marked weakness or impairedvision or hearing.
These are warming signalsthat the drug is causing problems. Whena reaction is unexpectedor severe a doctorshould be consulted immediately.
Not everyone reacts thesame way to medication. Oneperson may experience areaction to a certain drug,while another person mayhave no problems at all.
Food and Drug Interactions
Food can interact with drugs,making them work faster orslower or even preventingthem from working at all. Hereare examples:
Fatty foods, eaten beforethe anti-fungal drug griseofulvinis taken, can causeblood levels of the drug torise markedly. Calcium indairy products impairs absorptionof tetracycline, awidely used antibiotic. Citrusfruits or juices containingascorbic acid speeds the absorptionof iron from ironsupplements. Soda pop, fruitand vegetable juices withhigh acid contents (such asgrape, apple, orange ortomato) cause some drugs todissolve in the stomach insteadof the intestines wherethey can be more readily absorbed.
Large amounts of liverand leafy vegetables mayhinder the effectiveness ofanti-coagulants because vitaminK in these foods promotesblood clotting. Soybeans,rutabagas, brusselssprouts, turnips, cabbageand kale contain a substancethat inhibits production ofthyroid hormone; thus theycan interfere with thyroidmedications.
The most hazardous food-druginteraction is that ofdrugs sometimes prescribedfor severe depression of highblood pressure and foodscontaining the substancetyramine. The drugs involvedcontain monoamine oxidase(MAO) inhibitors. The foodsinvolved include aged cheese,Chianti wine, pickled herring,fermented sausages, yogurt,sour cream, chickenliver, broad beans, cannedfigs, bananas, avocados andfoods prepared with tenderizers. Mixingthese foods withan MAO inhibitor drug canraise the blood pressure todangerous levels.
Information for Patients The food-drug interactioncan go the other way. Oralcontraceptives, for instance,are known to lower bloodlevels of folic acid, a memberof the vitamin B family, andvitamin B6 although thedepletion i s usually not seriousenough to cause symptoms. Womenwho take birthcontrol pills would be wise toinclude dark green leafyvegetables in their diet.
Chronic use of antacidscontaining aluminum cancause phosphate depletion,leading to weakness, malaiseand loss of appetite.
Drugs and Smoking
Women on birth control pillswho smoke have an increasedrisk of heart attack,stroke and other circulatorydiseases.
Nicotine and other tobaccoconstituents speed up themetabolism of theophylline,an asthma drug, and pentazocine,a pain-killer, and to alesser extent certain tranquilizers,analgesics and anti-depressants. Thus,smokersmay need larger than normaldoses of these drugs. Whenthey stop smoking, dosage ofthese drugs may have to bechanged.
Smoking also can affectcertain diagnostic tests, suchas red and white blood cellcounts and blood clottingtime determinations.
Drugs and Alcohol
Chronic use of alcohol cancause changes in the liverthat speed up the metabolismof some drugs, such as anti-convulsants,anti-coagulantsand diabetes drugs. They becomeless effective becausethey do not stay in the bodylong enough.
Prolonged alcohol abusecan also damage the liver sothat it is less able to metabolizeor process certain drugs. Inthat case, the drugs stay inthe system too long. This isparticularly serious when thedrugs are phenothiazines(anti-psychotic drugs), whichcan cause further liverdamage.
Alcohol is a central nervoussystem (CNS) depressant. Alcoholtaken alongwith another CNS depressantdrug can affect performanceskills, judgment and alertness. Ifthe mixture includesoverdoses of barbiturates,diazepam (Valium) or propoxyphene(Darvon), the resultcan be fata.
A person who has developeda tolerance to thesedative effects of alcoholmay need larger doses oftranquilizers or sleeping pillsto get the desired effect. Thiscan lead to an overdose withoutthe person being awareof it.
Similarly, alcoholics andpatients with alcohol in theirsystem need larger amountsof anesthetics to inducesleep. Once such a patient is"under," his sleep is deeperand lasts longer.
Drugs and laboratory Tests
Drugs can affect the resultsof clinical laboratory tests. Forexample, excess use oflaxatives can affect tests todetermine calcium or bonemetabolism. Penicillin canresult in false readings ofprotein in the urine, a sign ofkidney disease. Large dosesof vitamin C can producefalse results in a urinaryglucose test for diabetes.
What You Should Tell Your Doctor
Because of these side effectsand drug interactions, it isimportant that you tell yourdoctor if you:
--Have had allergic reactions to drugs or foods, such as rashes or headaches.
--Are taking any medications on a regular basis, such as contraceptives or insulin, or if you use any non-prescription drugs on a routine basis.
--Are being treated for a different condition by another doctor.
--Are pregnant or breastfeeding.
--Have diabetes, kidney or liver disease.
--Are on a special diet or are taking vitamin and mineral supplements.
--Use alcohol or tobacco.
What You Should Ask Your Doctor
To get the most out of your medicine, you should ask your doctor:
--What is the name of the medicine? Write it down.
--What side effects might occur?
--How should you take the medicine? Does "three times a day" mean morning, noon and night? Should you take it before meals, with meals, or after meals? If the directions say "every six hours" do you have to get up during the night to take the medicine on time?
--How long should you take the medicine? If you stop just because you feel good, the symptoms and the disease may recur.
--Are there other medicines you should not take while you are taking this one?
--Are there any foods or beverages you should avoid?
How To Get the Best Results From Rx Drugs
--If a drug is not doing what it is supposed to do for you, check with your doctor. You may need a different dosage or a different drug.
--If you have an unexpected symptom--rash, nausea, dizziness, headache--report it to your doctor immediately.
--Don't stop taking your medicine just because you're feeling better. You may prevent the drug from doing its work completely.
--Check drug labels for specific instructions or warnings, such as 'do not take on an empty stomach" or "do not take with milk."
--Check the label, or ask the pharmacist, for storing instructions. Some drugs should be refrigerated; others must be protected from light.
--Always keep medicines out of the reach of children. Even though most prescription medicines come in childproof containers, children sometimes can open these bottles and swallow the contents. If you have difficulty opening such safety closures, you can request regular caps.
--Never let another person use your medicine and never take medicine prescribed for anyone else. Your symptoms may look the same, but you may be suffering from an entirely different problem.
--Never take medicines without checking the label to make sure you're taking the right one. Don't take medicine at night without turning on the light.
--Do not keep prescription drugs that are no longer needed. Destroy leftover medicines by flushing them down the toilet and dispose of containers carefully so children can't get them.
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|Publication:||Pamphlet by: Narcotic Educational Foundation of America|
|Date:||Jun 20, 1991|
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