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C H A P T E R 9  Antibiotics

who have severe GI disease or who are debilitated. (See Box 9.1 for effects of antibiotics across the lifespan.) The antibiotic of choice is one that affects the causative organism and leads to the fewest adverse effects for the person involved. In some cases, antibiotics are given in combination because they are synergistic ; meaning their combined effect is greater than their effect if they are given indi- vidually (Box 9.2). Use of synergistic antibiotics also allows the person to take a lower dose of each antibiotic to achieve the desired effect, which helps to reduce the adverse effects that a particular drug may have. In some situations, antibiotics are used as a means of prophylaxis, or prevention of potential infection. People who will soon be in a situation that commonly results in a specific infection (e.g. people undergoing GI surgical procedures, which may introduce GI bacteria into the bloodstream or peritoneum) may be given antibiotics before they are exposed to the bacteria. Usually a large, Children are very sensitive to the gastrointestinal and central nervous system (CNS) effects of most antibiotics, and more severe reactions can be expected when these drugs are used in children. It is important to monitor the hydration and nutritional status of children who are adversely affected by drug-induced diarrhoea, anorexia, nausea and vomiting. Superinfections can be a problem for small children as well. For example, thrush (oral candidiasis) is a common super-infection that makes eating and drinking difficult. Many antibiotics do not have proven safety and efficacy in paediatric use, and extreme caution should be used when giving them to children.The fluoroquinolones, for instance, are associated with damage to developing cartilage and are not recommended for growing children. Paediatric dosages of antibiotics should be double- checked to make sure that the child is receiving the correct dose, thereby improving the chance of eradicating the infection and decreasing the risk of adverse effects. Antibiotic treatment of ear infections, a common paediatric problem, is controversial. Ongoing research suggests that judicious use of decongestants and anti- inflammatories may be just as successful as the use of antibiotics without the risk of development of resistant bacterial strains. Parents, not wanting to see their child sick, may demand antibiotics as a cure-all whenever their child is fussy or feverish. Parent education is very important in helping to cut down the unnecessary use of antibiotics in children. ADULTS Many adults believe that antibiotics are a cure-all for any discomfort and fever. It is very important to explain that antibiotics are useful against only specific bacteria and BOX 9.1 Antibiotics CHILDREN

one-time dose of an antibiotic is given to destroy any bacteria that enters the host immediately and thereby prevent a serious infection.

■■ BOX 9.2  Using combination drugs to fight resistant bacteria

Clavulanic acid protects certain beta-lactam antibiotics from breakdown in the presence of penicillinase enzymes. A combination of amoxycillin and clavulanic acid ( Augmentin ) is commonly used to allow the amoxycillin to remain effective against certain strains of resistant bacteria (usual dosage, 250–500 mg PO q 8 hours for adults or 20–40 mg/kg/day PO in divided doses for children). The theory behind the combination of ticarcillin and clavulanic acid ( Timentin ) is similar (usual dosage 3.1 g IM q 4–6 hours for adults; safety not established for children).

Drug therapy across the lifespan

actually can cause problems when used unnecessarily for viral infections, such as the common cold. Adults need to be cautioned to take the entire course of the medication as prescribed and not to store unused pills for future infections or share antibiotics with symptomatic friends. PREGNANCY AND BREASTFEEDING Women who are pregnant or breastfeeding should not take antibiotics unless the benefit clearly outweighs the potential risk to the fetus or neonate.Tetracyclines, for example, are associated with pitting of enamel in developing teeth and with calcium deposits in growing bones.These drugs can cause serious problems for neonates. Women of childbearing age should be advised to use barrier contraceptives if any of these drugs are used. Many antibiotics interfere with the effectiveness of oral contraceptives and unplanned pregnancies can occur. OLDER ADULTS In many instances, older adults do not present with the same signs and symptoms of infections as other people.Therefore, assessing the problem and obtaining appropriate specimens for culture is especially important with this population. Older people may be more susceptible to the adverse effects associated with antibiotic therapy.Their hydration and nutritional status should be monitored closely, as should the need for safety precautions if CNS effects occur. If hepatic or renal dysfunction is expected (particularly in very old people, those who may depend on alcohol, and those who are taking other hepatotoxic or nephrotoxic drugs), the dose may need to be lowered and the person should be monitored more frequently. Elderly people also need to be cautioned to complete the full course of drug therapy, even when they feel better, and not to save pills for self-medication at a future time.