A Pharmacist Clears Up Misconceptions About Antibiotics

Drug Allergy vs. Side Effects

Drug allergy usually begins with a rash. The typical antibiotic rash involves large areas of the body and is usually itchy. The spots usually come and go, leaving purplish spots as they go away. Dangerous drug allergy can include swelling, and is of special concern if the swelling is in the face. An extreme allergic reaction is called "anaphylaxis." Anaphylaxis is an emergency that can cause difficulty breathing and shock. Anaphylaxis can be life threatening if not treated immediately.

If a drug allergy is suspected, it is usually best to let the doctor see the patient to verify that the reaction is an allergic one. Some rashes are not true allergy and may not be a reason to withhold the medication in the future. If the doctor verifies the allergy, a written record should be made and kept with the patient. The patient's pharmacist should always be notified so that the allergy information can be added to his medication profile.

When a patient has upset stomach, nausea, and/or diarrhea, but no rash or swelling, that does not mean he is allergic to the medication. Those symptoms are side effects of the antibiotic. They occur because the antibiotic kills some of the body's good bacteria too. Side effects such as diarrhea or nausea may or may not occur the next time the medication is taken. A side effect may not occur at all with a different dose of the same medication.

If a side effect is wrongly reported as an allergic reaction, this narrows the list of drugs that can be given to the patient. It would be a shame to need a certain antibiotic and have it withheld because the physician, based on the patient's erroneous reports, believed there was an allergy. When an allergy to an antibiotic is present, it means that the entire class of drugs that that antibiotic belongs to is off limits to the patient. At some point, that class of drugs might be desperately needed to treat a specific, possibly life-threatening, infection that no other drug can treat. What a tragedy if the patient cannot be given the drug he needs because a drug allergy notation, based on a misunderstanding, became a permanent part of his medical record.

Antibiotic Selection

Doctors and pharmacists sometimes hear, "Give me (such-and-such) antibiotic. It works great on me."

To understand why that statement is useless to the doctor, you have to understand that an antibiotic is chosen based on a specific suspected bacterial cause. Not all bacteria are sensitive to all antibiotics. If a patient has strep throat today, he may be given amoxicillin. If different bacteria cause his sore throat next time, he may need an entirely different antibiotic that specifically kills very different bacteria.

The doctor may take a sample and order a culture and sensitivity. In the meantime, an antibiotic will be selected based on what bacteria he or she suspects to be causing the infection. When the culture results are received, the antibiotic may need to be changed based on sensitivity reports.

Sometimes a microscopic exam will tell the doctor which antibiotic to start. Sometimes the selection is based on experience with frequent recent infections, all giving the same clinical picture. In any case, the physician will select a particular antibiotic based on the most likely offending bacteria.

Another consideration in selecting the right antibiotic is whether or not it is indicated for infections in a certain part of the body. An antibiotic that can be used to treat an infection in the urine, for example, may not reach high enough concentrations in the tissues to be an effective treatment for a skin abscess.

Taking an Antibiotic Until It Is Gone

When a dose of an antibiotic is taken, part of the bacteria is killed. The next dose kills a part of the bacteria that remained from the previous dose. The next dose kills a part of those remaining bacteria. However, when a dose is skipped, there is some re-growth of bacteria. That re-growth may completely replace what was killed with the previous dose, plus some. If very many doses are skipped, the bacteria may grow faster than they are killed.

After a few days of a course of antibiotics, the patient may begin to feel remarkably better. The bacteria that are present will have been killed off to the point where symptoms are no longer experienced. That does not mean that there are no bacteria. If the antibiotic is stopped prematurely, the bacteria will usually grow back and the patient will have a relapse.

Comparing the Strength of One Antibiotic to Another

Sometimes a patient will say something like, "I am only getting 250 mg of this antibiotic? Last time I had a throat infection, I got 750 mg of an antibiotic." This statement indicates that the patient believes that 1 mg of one antibiotic is equal to 1 mg of another. The mg is only expressing the weight of the active ingredient in milligrams. The weight of one antibiotic cannot be compared to the weight of another just like a pound of oranges cannot be said to equal a pound of cucumbers. They are different. The weight of a dose of an antibiotic can only be effectively compared to the weight of another dose of that same antibiotic, but not to a different antibiotic. In other words, 250 mg of tetracycline is a smaller dose than 500 mg of tetracycline. To compare 250 mg of tetracycline to 250 mg of Biaxin yields no meaningful results.

Antibiotics with Food

Sometimes a pharmacy patron says, "I always take my antibiotics with food." Some antibiotics are not well absorbed with food and cannot reach therapeutic concentrations in the body when taken with food. Some are better absorbed when taken with food. Be sure you know whether to take your medicine on an empty stomach or with food.

To Crush or Not to Crush

Medications are available in all sorts of delivery vehicles. Some should never be crushed or chewed. An example is a medication that is formulated in a time-released tablet with layers that are designed to dissolve at different times. If that tablet is crushed, the medication will be released into the bloodstream all at once instead of slowly, as intended. This can result in an overdose.

Sometimes a medication is coated to make it dissolve past the stomach, at a certain place in the intestine. If it is crushed, the medication will be released immediately and may be completely destroyed by stomach acid, effectively causing the infection to go untreated.

Other medications may be pressed into matrices that are released slowly as the tablets move through the gut. When all the medication is released, the matrix may be passed, whole, into the toilet. If it had been crushed, the medication would not work as intended.

Refrigerate Liquids-or Not?

Not all medications are best stored in the refrigerator. Some, like Biaxin, are more stable at room temperature. Some, like amoxicillin, can be stored in the refrigerator to improve flavor, but are also stable at room temperature. Some, like Keflex, are more stable if stored in the refrigerator. Find out how to store the medication properly and follow those instructions. To store a medication too cold or too hot make cause it to be less effective.

To Save or Not to Save

The best reason not to save an antibiotic is that it is supposed to be taken until it is gone. If the doctor has switched you to another antibiotic in mid-course because you were not improving or because culture results showed another antibiotic to be a better choice, it still should not be saved. How will you know it is the right choice next time? You could waste valuable time or even cause the infection to worsen by taking the wrong antibiotic.

Children's antibiotic suspensions usually come as a powder and they are mixed with water before dispensing. After they are mixed, most of them are good for periods of time ranging from ten to fourteen days. They should not be kept past that time because they will have lost their potency.

The Color of the Medicine

Patients should not refer to a medication as "that pink one" or by some other descriptive. There are many, many antibiotics that are pink. If there has been a serious reaction in the past and all the patient knows is what color the medicine was, there can be a disastrous outcome. Learn, or at least write down, the names of the medications you are taking regularly or have had a bad reaction to. It may save your life.