HOW TO CHOOSE MOST APPROPRIATE ANTIBACTERIAL CHEMOTHERAPY?

Choosing an antibacterial drug therapy can depend on various factors which are mentioned below:

BACTERIOSTATIC V/S BACTERICIDAL
Antibacterial chemotherapeutic agents can be categorized as bacteriostatic and bactericidal on the basis of their interaction with the targeted bacterial pathogens.
Bacteriostatic drugs work by inhibiting the growth of specific bacteria. Static drugs work by reversibly inhibiting the growth i.e. if the agent (drug) is removed or if its effect if over, the microorganism will get recovered and will grow again causing the same infection again.
Bactericidal drugs work by directly killing the target bacteria from the location. Cidal drugs may act as static drugs at low concenteration.

Use of any drug also depends on the immune system of the host because static drug does not completely eliminate the target bacteria. For patients with strong immune system, either static or cidal drugs can be used for curing infection while in case of immunocompromised individual, only cidal drugs are essentially required for complete removal of the bacterial infections.

SPECTRUM OF ACTIVITY
On the basis of their range or spectrum of activity, the chemotherapeutic agents can be broadly categorized into 5 different categories:

1. Narrow spectrum antibiotics are only active against less no. of microorganisms. They target only a specific strains of bacterial pathogens, especially gram positive bacteria.
2. Moderate spectrum antibiotics target most of the gram positive bacterial pathogens as well as most systemic, enteric and urinary tract gram negative bacterial pathogens.
3. Narrow and moderate spectrum antibiotics are known to cover all the β-lactam antibiotics which can effectively work against gram positive and negative bacteria. Some members of this classification are only effective against gram negative while others can also kill gram positive bacteria.
4. Broad spectrum antibiotics, as the name suggests targets a broad range of bacterial pathogens which includes almost all the prokaryotic organisms except mycobacteria and pseudomonas. They are also effective against polymicrobic infections (mixed infections caused by multiple bacterial species). It is used when other spectrum antibiotics fail to treat infections due to drug resistance. There is a risk of superinfection while using broad spectrum antibiotics.
5. Anti-mycobacterial antibiotics are only effective against mycobacterial strains of pathogenic bacteria.

DOSAGE AND ROUTE OF ADMINISTRATION
• Dosage –
The minimum or maximum amount of drug that a patient is given is the dosage of the drug. The dosage of the particular drug needs to be determined carefully to ensure that the optimum level of that particular drug is achieved at the site of infection for the elimination of the infection without causing any toxic side effects. Therefore, the selection and standardization of dosage of a particular drug is done so that it has the minimum side effect.
• Route of administration –
It can be defined as the method by which a drug is introduced in the patient’s body. There are different ways of administration of a drug. The most preferred drugs are the one that can be administered orally because it is easier for the patients to take them even at their home without visiting the health care professionals again and again. However, it is observed that not all drugs can be absorbed from the gastro intestinal tract. E.g. Bacitracin, Polymyxin and many antifungals. These drugs may be available to the patients in the form of topical preparations so that they can be applied for the treatment of superficial skin infections.
The another condition arises when a patient is unable to take oral drug initially due to some illness like vomiting. In that condition, the drug is preferably administered through parenteral route i.e. intramuscular or intravenous injections. In general, for most of the drugs, the drug levels in plasma introduced via intravenous is higher than that of oral or intramuscular route.

POTENTIAL FOR SIDE EFFECTS
The adverse effects which are seen in the patient’s body after administration of any drug can be classified into 3 main types:

1. PHARMACOLOGICAL SIDE EFFECTS
   These are the toxic side effects which the drug shows by damaging the infected or even healthy cells by the production of some toxic chemicals on cell surface or their interior.
2. ALLERGIC SIDE EFFECTS
   Some drugs show the allergic reactions in the patient’s body which is due to the antigen-antibody reaction which in turn effects other cells and show some allergy.
3. BIOLOGICAL TYPE SIDE EFFECTS
   This type of side effect is worst and it involves interference of the drug with the normal microflora of the body which is followed by either local chemical damage or superinfection.

POTENTIAL INTERACTION BETWEEN DRUGS
Most of the time, antibiotics are administered in the patient’s body as a single agent but many time it becomes necessary to take two or more drugs at a time. So, different drugs administered at a single time show some interaction among them.
The interaction may be positive or negative.
Sometimes, a synergistic or positive interaction is shown by two antibiotics when they are administered together. Some drugs show bactiostatic effect when used as a single agent but are able to show bactericidal effect when combined with other antibiotic.
On the other hand, some drugs when used together show negative effect or antagonistic effect. Antagonism can occur between two antimicrobial or between one antimicrobial and one non-antimicrobial. The antagonistic interactions thus cause toxic side effects, loss of drug activity, decreased effect of drug at the site of infection. For e.g. Penicillin and bacteriostatic drugs are antagonists of each other.