Erythromycin and Other Macrolides

Erythromycin and the other macrolides exhibit a very broad spectrum of antibacterial activities and are active against many gram-positive bacteria, as well as some gram-negative bacteria. These agents are often used as the primary or alternative drug in a variety of clinical conditions (see Table 33-5). Macrolides may be especially useful in patients who are allergic to penicillin. 

Macrolides may produce other beneficial effects that compliment their antibacterial properties. These 

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Like fluoxetine, erythromycin and other macrolides inhibit the CYP-3A isoenzyme and increase the levels and effects of the triazolobenzodiazepines (Shader and Greenblatt, 1995 Chouinard et ah, 1999). Midazolam should be avoided or the dosage dropped by 50% in patients receiving erythromycin (Olkkola et ah, 1993). Ketoconazole and itraconazole may also interact with triazolam and midazolam, and combinations of these drugs should be avoided (Varhe et ah, 1994 Chouinard et ah, 1999). 

Erythromycin Erythromycin is incompatible with preparations that are highly acidic or alkaline in nature. Pancreatitis disorders are reported with erythromycin overdose. Erythromycin and other macrolides interact with other drugs and are detailed elsewhere.6... 

Peeters TL. Erythromycin and other macrolides as pro-kinetic agents. Gastroenterology 1993 105(6) 1886-99. 

C. Erythromycin and other macrolide antibiotics bind the SOS subunit near the P-site and canse conformational changes that inhibit the translocation of peptidyl tRNA from the A-site to the P-site. 

Peelers, T. L. (1993). Erythromycin and other macrolides as prokinetic agents. Gastroenterology 105, 1886-1899. 

Tateda, K., Hirakata, Y., Furuya, N., Ohno, A., and Yamaguchi, K. (1993). Effects of sub-MlCs of erythromycin and other macrolide antibiotics on serum sensitivity of Pseudomonas aeruginosa. Antimicrob. Agents. Chemother. 37, 675-680. 

Echuzen H, Kawasaki IL Oiiba K, Tani M. Ishizaki T. A potent inhibitory effect of erythromycin and other macrolide antibiotics on the mono-N-dealkylatiyra-mide with human liver microsomes. J Pharmacol Exp Ther (1993) 264,1425-31. 

Macrolides, both erythromycin and others, inhibit the synthesis of bacterial proteins. The primary mechanisms of protein synthesis are identical in humans and bacteria. However, there is a significant difference that allows a specific antibiotic to exhibit selective toxicity with respect to bacteria. 

Nefazodone substantially decreases the clearance rate for triazolam, which results in a 400% increase in triazolam s serum levels (131). Erythromycin can also interfere with the metabolism of triazolam, resulting in decreased clearance and increased plasma levels, possibly causing toxicity. Troleandomycin and other macrolide antibiotics, such as clarithromycin, flurithromycin, josamycin, midecamycin, or roxithromycin, also may inhibit triazolam s metabolism (132). The coadministration of itraconazoie and triazolam can produce a marked elevation of triazolam plasma levels associated with statistically significant impairment of psychomotor tests and a prolongation of other effects (e.g., amnesia, lethargy, and confusion) for hours after awakening ( 133). 

With the important exception of additive effects when combined with other CNS depressants, including alcohol, BZDs interact with very few drugs. Disulfiram (see the section The Alcoholic Patient in Chapter 14) and cimetidine may increase BZD blood levels, and diazepam may increase blood levels of digoxin and phenytoin. Antacids may reduce the clinical effects of clorazepate by hindering its biotransformation to desmethyidiazepam. Coadministration of a BZD and another drug known to induce seizures may possibly increase seizure risk, especially if the BZD is abruptly withdrawn. Furthermore, as noted earlier, important interactions have been reported among nefazodone, erythromycin, troleandomycin, and other macrolide antibiotics, as well as itraconazole. In each case, metabolism is inhibited, and triazolam levels can increase significantly. 

M scrofuiaceum Cervical adenitis in children Amikacin, erythromycin (or other macrolide), rifampin, streptomycin (Surgical excision is often curative and the treatment of choice.)... 

Accumulation of the parent drug and resultant QT prolongation may occur following a overdose, a drug interaction that limits metabolism of terfenadine (e.g., concomitant administration with erythromycin or other macrolide antibiotic or with the azole derivatives ketoconazole or itraconazole), or significant hepatic dysfunction that limits metabolism of terfenadine. Patients with preexisting cardiac disease or those with electrolyte abnormalities are also at increased risk for cardiac toxicity. 

Although the majority of mechanistic studies have used erythromycin, all other macrolides as well as the lincosamides and streptogramins (collectively known as MLS antibiotics) are believed to operate by a similar mechanism [216]. However, each of the groups possesses slightly different, but overlapping, ribosomal binding domains [217]. 

Specific concomitant medications or consumptions (check specific statin package insert for warnings) fibrates (especially gemfibrozil, but other fibrates too), nicotinic acid (rarely), cyclosporine, azole antifungals such as itraconazole and ketoconazole, macrolide antibiotics such as erythromycin and clarithromycin, protease inhibitors used to treat Acquired Immune Deficiency Syndrome, nefazodone (antidepressant), verapamil, amiodarone, large quantities of grapefruit juice (usually more than 1 quart per day), and alcohol abuse (independently predisposes to myopathy)... 

The complete degradation of sulfamethoxazole was also reported within 14 days with P. chrysosporium, Bjerkandera sp. R1 and B. adusta [4], although, contrary to the reports of enzymatic transformation, metabolites were not identified. Partial removal (from 30% to 55%) of sulfamethoxazole from activated-sludge-mixed liquor and the effluent of a WWTP was demonstrated at bench scale within 5 days with P. chrysosporium propagules entrapped in a granular bioplastic formulation [25]. This approach was also successful in the partial elimination of other kinds of antibiotics, eg., ciprofloxacin (see below) and the macrolide erythromycin. 

Secondary metabolites generated via the propionate route are quite unusual in nature. Relevant exceptions are some antibiotic macrolides from Streptomycetes [42], but wholly propionate-derived macrolides are rare. This biosynthetic pathway has been well proved for erythromycin (13), where the aglycone is produced by assembling seven propionate units [43, 44], and for a few related antibiotics [45]. However, very sophisticated biosynthetic experiments [46] have established that some apparent propionate units in other macrolides (e.g., aplasmomycin [46]) from Streptomycetes could be formed either by C-methylation through S-adenosylmethionine or from glycerol. 

Clarithromycin is better absorbed and irritates the gastrointestinal tract less than erythromycin. It is presumed that its activity exceeds that of erythromycin by 2-4 times with respect to a number of streptococci and staphylococci, and to a few other microorganisms. It is used for treating bacterial bronchitis, pneumonia, skin and sexual infections. It is believed that clarithromycin is the most active macrolide for treating atypical mycobacteria. Synonyms of this drug are biaxin and others. 

Erythromycin and the other macrolides prevent release of tRNAs from the ribosomal A site after peptide bond formation. 

Carbamazepine also can induce the enzymes that metabolize other anticonvulsant drugs, including phenytoin, primidone, phenobarbital, valproic acid, clonazepam, and ethosuximide, and metabolism of other drugs the patient may be taking. Similarly, other drugs may induce metabolism of carbamazepine the end result is the same as for autoinduction, and the dose of carbamazepine must be readjusted. A common drug-drug interaction is between carbamazepine and the macrolide antibiotics erythromycin and trolean-domycin. After a few days of antibiotic therapy, symptoms of carbamazepine toxicity develop this is readily reversible if either the antibiotic or carbamazepine is discontinued. 

BZD hypnotics such as midazolam and triazolam are primarily metabolized via the P450 3A3/4 microenzyme system. Other BZDs often used as hypnotics, such as diazepam, can also be metabolized by CYP 33/4 and CYP 2C19. Any drugs that act as inhibitors or inducers of these isoenzymes could increase or decrease BZD levels, respectively (350). Thus, ketoconazole, macrolide antibiotics (e.g., erythromycin), SSRIs (e.g., fluoxetine-norfluoxetine and fluvoxamine), and other antidepressants (especially nefazodone) may decrease clearance and increase BZD levels to potentially toxic ranges. Conversely, rifampacin, CBZ, and dexamethasone may increase clearance and decrease BZD levels to potentially subtherapeutic ranges. 

The risk of myopathy appears to be increased by high levels of HMG-CoA reductase inhibitory activity in plasma. Lovastatin is metabolized by the CYP isoform 3A4. Certain drugs, that share this metabolic pathway can raise the plasma levels of lovastatin and may increase the risk of myopathy. These include cyclosporine, itraconazole, ketoconazole and other antifungal azoles, the macrolide antibiotics erythromycin and clarithromycin, HIV protease inhibitors, the antidepressant nefazodone, or large quantities of grapefruit juice (greater than 1 quart daily)... 

Macrolides. Antibiotics in the macrolide group are macrocyclic lactones that can be further classified into two main subgroups (I) polyene macrolides that are antifungal agents and include compounds like nystatin and amphotericin B and (2) antibacterial antibiotics represented by erythromycin and tylosin. A number of other subfamilies of antibacterial and antifungal antibiotics fall into the broad category of macrolides,... 

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