Preparing to Administer Antimicrobial Medication - Pharmacology

Antimicrobial medication requires the nurse to follow the same general administration procedures that are required for any type of medication. The most critical step is to determine if the patient has allergies to drugs, food, environmental stimuli, and a family history of allergies to antibiotics. There is also a high incidence of cross sensitivity between some antibiotics such as penicillin and cephalasporins. Always display allergies in red and clearly write them on the patient’s record. Even if the patient’s record indicates that the patient doesn’t have allergies, always ask the patient each time you administer the antimicrobial medication.

Always have emergency medications such as epinephrine, Benadryl, and steroids handy so they can be given to counteract any adverse side effect of the antimicrobial medication. Be sure to carefully monitor the patient for a half hour after the medication is given to determine if the patient experiences an adverse reaction.

During treatment, you’ll need to monitor the therapeutic effect of the medication by monitoring the signs and symptoms of the disease and by obtaining the patient’s white blood cell count. Although you can monitor the antimicrobial serum level to determine if the medication has achieved a therapeutic level, this is only done in cases where the therapeutic range is narrow resulting in possible toxicities (i.e., vancomycin ototoxicity).

It is important to administer antimicrobials at the times described in the pre-scriber’s order in order to maintain a therapeutic blood level of the medication. Otherwise, this can lead to undertreatment or ineffective treatment if not main-tained. Sometimes a double dose of an antibiotic is administered as the first dose to quickly achieve a therapeutic level. This is called a loading dose.

Intramuscular injections of antibiotics should be given deep into the muscle and sites should be rotated if more than one injection is prescribed. Stop orders and the need for renewal orders will depend on the healthcare agency policy. However, it is common that antibiotic orders are for 72 hours only until the results of a culture and sensitivity test can be obtained. Antibiotic prescriptions are usually not renewed. This is an effort to limit the opportunity for the microbial to become resistant to the medication.

In severe cases, aggressive treatment is necessary to control the growth and destroy the microbial quickly. To do this, the medication is administered par-enterally in an IV dose that is diluted in a neutral solution (pH 7.0 to 7.2) such as normal saline (N.S.) or isotonic sodium chloride or 5% dextrose and water (D5W). Antibiotics should not be mixed together or administered at the same time. They can be administered as a piggyback infusion. Information about how long an interval should occur between the infusion of different antibiotics should be obtained from the pharmacy or the drug insert.

The following nursing diagnoses can be used for patients who are taking antibiotics:

  • Risk of infection related to treatment failure or superinfection.
  • Risk of fever related to treatment failure or superinfection.
  • Risk of fluid volume deficit related to adverse GI reaction such as anorexia, nausea/ vomiting/ diarrhea, and complications of allergic reaction.

They are also at risk for having the following collaborative problems:

  • Sepsis
  • Ototoxicity (ears)
  • Blood dyscrasias
  • Nephrotoxicity (kidney)

It is critical that the patient be given information on the management of his or her condition. These instructions include:

  • Take all the medication even after the symptoms subside.
  • Do not take medication that is left over from a previous illness. (The medication may not treat the patient’s condition or may have lost its therapeutic capabilities.)
  • Do not share drinks, food, and utensils with others until the healthcare provider determines that the patient is no longer infected by the microbial. Sharing may enable the microbial to spread to other people.
  • Recognize the expected effects, side effects, and adverse reactions that might occur as a result of taking the medication. Also provide the patient with a telephone number to call if the patient has questions about these effects.
  • Wear a Med-alert bracelet if the patient has allergies to medication.


Penicillin (PCN) is derived from molds that you sometimes see on bread and fruit. It was discovered in 1940 and remains the most effective and least toxic antimicrobial drug. Penicillin weakens the cell wall of a bacteria resulting in the rupture and destruction of a cell, which is called lysis.

Penicillin is most active against gram-positive bacteria and some gram-negative bacteria. However, it isn’t active against bacteria that contain enzymes that destroy penicillin.

There are four types of penicillin:

  1. Basic (natural)
  2. Penicillinase-resistant (resistant to beta-lactamase inactivation)
  3. Aminopenicillins (broad spectrum)
  4. Extended-spectrum

Besides route, dose, and time, drugs are also characterized by pregnancy category, protein-binding, and half-life. Pregnancy category indicates if the drug has been tested using pregnant women and how safe the drug might be if used during pregnancy. Penicillin is categorized by its usefulness against bacterial enzymes capable of destroying the drug. Four different classifications of antibiotics exist that contain the beta-lactam ring and are more active against gram-negative cell wall organisms and decrease its susceptibility to enzymes that inactivate the antibiotic. Protein-binding is when a drug binds to plasma proteins. When a drug is bound to a protein it is not available for therapeutic use. The percent of protein binding is the amount of drug that can’t be used until it is released when the free drug or the amount not bound to protein is excreted from the body. Half-life is the amount of time for half the drug to be eliminated from the body.

The category appears at the top of the table if the value of the category applies to all the drugs in a table, otherwise the category appears beneath the name of the drug in the table.

There are several precautions that must be taken when administering penicillin. If penicillin is given PO, avoid giving this medication an hour before and an hour after the patient has eaten. However, food doesn’t have any effect on amoxicillin, amoxicillin and clavulanate, and bacampicillin. Give penicillin with a full glass of water and not with acidic fruit juices.

If penicillin is administered IV, give it slowly because penicillin contains a large amount of potassium that can cause heart failure in patients with renal insufficiency. Before penicillin is administered, the patient must be assessed for a number of conditions. One of the most important is allergies. An allergic reaction to penicillin can be anywhere from a mild rash to anaphylactic shock and death.

Furthermore, don’t administer penicillin to patients who have:

  • A tendency to bleed.
  • Ulcerative colitis and other GI diseases.
  • Mononucleosis (a skin rash may develop with use of ampicillin or bacampicillin).
  • A low-salt diet (parenteral carbenicillin and ticarcillin have high sodium content
  • Impaired renal function (a lower dose may be given in such cases).

After penicillin is administered, monitor the patient for:

  • Serum electrolytes for hyperkalemia (elevated potassium) and/or hyperna- turemia (elevated sodium)
  • Unusual weight loss (especially in the elderly)
  • Vital signs
  • WBC
  • Cultures
  • Prothrombin Time (PT) (bleeding times)

Descriptions of medication throughout this chapter use the following abbreviations:








Penicillin can produce adverse effects if it is administered in conjunction with other drugs. This is the situation with giving penicillin with an anti-hypertensive such as Captopril (angiotensin-converting enzyme [ACE] inhibitors), potassium-sparing diuretics such as Aldactone, potassium-containing drugs, or potassium supplements such as Kay Ciel. The combination of drugs may increase the patient’s potassium level (hyperkalemia) and therefore require that the patient’s serum potassium levels be carefully monitored while the patient receives penicillin.

There is an increased risk of bleeding when administering high doses of parenteral carbenicillin or ticarcillin as these drugs inhibit platelet aggregation. These penicillins also increase the risk for severe bleeding if given with thrombolytic agents such as streptokinase.

The absorption of penicillin G when taken PO may be decreased if taken with cholestyramine (Questran) or colestipol (Colestid). Similarly, the use of penicillin might decrease the effectiveness of estrogen contained in contraceptives.

Two other drugs affected by penicillin are methotrexate (Folex) and probenecid (Benemid). There is a decrease in the body’s ability to clear methotrexate when penicillin is present. There can be a build up of methotrexate resulting in toxicity.

Probenecid decreases renal secretion of penicillin resulting in an increase of the serum level of penicillin.

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