Ethambutol/streptomycin

The optic nerve is of interest here because some drugs are toxic to this tissue.The antibiotics chloramphenicol, ethambutol, streptomycin, and sulfonamides can cause optic neuritis. Vitamin A, especially in large doses, can result in papilledema. Digitalis can cause retrobulbar neuritis (see Chapter 35). 

There were four cases of agranulocytosis due to antituberculosis drugs (rifampicin, isoniazid, ethambutol, streptomycin, or pyrazinamide) among about 6400 patients who underwent chemotherapy from 1981 to 2002 the incidence rate of agranulocjhosis was estimated at 0.06% (36). 

Of 26 patients who received rifabutin 600 mg/day in combination with ethambutol, streptomycin, and either clarithromycin (500 mg bd n — 15) or azithromycin (600 mg/day n — 11), there were rifabutin-related... 

Pneumococci resistant to penicillins, certain cephalosporins, and macrolides are increasingly common. These organisms generally are susceptible to vancomycin, the new fluoroquinolones, and cefotaxime or ceftriaxone. M. tuberculosis resistant to one or more first-hue anti-tubercular agents (e.g., isoniazid, rifampin, ethambutol, streptomycin, and pyrazinamide) have increased in frequency as well. This has been... 

The initial phase must contain three or more of the following drugp isoniazid, rifampin, and pyrazin-amide, along with either ethambutol or streptomycin. The CDC recommends treatment to begin as soon as possible after the diagnosis of tuberculosis. The treatment recommendation regimen is for the administration of rifampin, isoniazid, and pyrazinamide for a minimum of 2 months (8 weeks), followed by rifampin and isoniazid for 4 months (16 weeks) in areas with a low incidence of tuberculosis. In areas of high incidence of tuberculosis, the CDC recommends the addition of streptomycin or ethambutol for the first 2 months. 

This chapter will discuss the following primary aiititubercular drugp ethambutol, isoniazid, pyrazin-amide, rifampin, and streptomycin. Other primary and secondary drugp are listed in the Summary Drug Table Aiititubercular Drugp. 

Because they are hepatically cleared, isoniazid and rifampin do not require dose modification in renal failure.31,36,39 Pyrazinamide and ethambutol typically are reduced to three times weekly to avoid accumulation of the parent drug (ethambutol) or metabolites (pyrazinamide).28,31 Renally cleared TB drugs include the aminoglycosides (e.g., amikacin, kanamycin, and streptomycin), capreomycin, ethambutol, cycloserine, and lev-ofloxacin.28,31,33,39 Dosing intervals need to be extended for... 

Anti my cob ac t er ials Isoniazid Rifampin Ethambutol Pyriz inamide Streptomycin... 

The answer is c. (Hardman, pp 1161-1162.) An important problem in the chemotherapy of TB is bacterial drug resistance For this reason, concurrent administration of two or more drugs should be employed to delay the development of drug resistance. Isoniazid is often combined with ethambutol for this purpose. Streptomycin or rifampin may also be added to the regimen to delay even further the development of drug resistance. 

Drugs of choice are isoniazid, rifampin, ethambutol, along with streptomycin and pyrazinamide. Less well tolerated, second-line agents include p-aminosal-icylic acid, cycloserine, viomycin, ka-namycin, amikacin, capreomycin, ethionamide. 

The initial phase of the regimen must contain at least 3 of the following drugs Isoniazid, rifampin, and pyrazinamide, along with either ethambutol or streptomycin if the local resistance pattern to isoniazid is not documented or is greater than 4%. 

Do not use tuberculosis regimens consisting of isoniazid, ethambutol, and pyrazinamide (ie, 3-drug regimens that do not contain a rifamycin, an aminoglycoside [eg, streptomycin, amikacin, kanamycin], or capreomycin) for the treatment of patients with HIV-related tuberculosis. The minimum duration of therapy is 18 months (or 12 months after documented culture conversion) if these regimens are used for the treatment of tuberculosis. 

The 6-month regimen Ordinarily this consists of an initial 2-month phase of rifampin, isoniazid, and pyrazinamide and, if clinically indicated, streptomycin or ethambutol, followed by 4 months of rifampin and isoniazid. Reassess the need for a fourth drug when the results of susceptibility testing are known. If community rates of INH resistance are currently less than 4%, an initial treatment regimen with less than 4 P.1008... 

Mycobacterium tuberculosis Add streptomycin or ethambutol as a fourth drug in a regimen containing isoniazid (INH), rifampin, and pyrazinamide for initial treatment of tuberculosis unless the likelihood of INH or rifampin resistance is very low. Streptomycin also is indicated for therapy of tuberculosis when one or more of the above drugs is contraindicated because of toxicity or intolerance. 

Among the antimycobacterials often a differentiation is made between first-choice and second-choice agents. The first-choice agents include iso-niazid, rifampicin, ethambutol, pyrazinamide and streptomycin or as alternatives the other aminoglycosides amikacine or kanamycine. The second-choice agents include the quinolones ciprofloxacin and ofloxacin and also the rifamycin derivative rifabutin. 

In some patients, the combination of antiretroviral agents may be so complex that the use of antituberculosis regimens containing no rifamycins may be considered. For such patients, a 9-month, largely intermittent, regimen consisting of isoniazid, streptomycin, pyrazinamide and ethambutol for 2 months then isoniazid, streptomycin, and pyrazinamide for 7 months is an option. 

The most commonly used regimen for drug-susceptible tuberculosis consists of isoniazid, rifampin, and pyrazinamide daily for 2 months, followed by isoniazid and rifampin daily or two to three times a week for 4 months. If isoniazid resistance is suspected, ethambutol or streptomycin should be added to the regimen until the susceptibility of the mycobacterium is determined. This... 

DNA synthesis inhibitors Fluoroquinolones Antimycobacterials Isoniazid Rifampin Ethambutol Pyrizinamide Streptomycin... 

Mycobacterium tuberculosis Isoniazid + rifampin + ethambutol + pyrazinamide Streptomycin, moxifloxacin, amikacin, ethionamide, cycloserine, PAS, linezolid... 

Streptomycin (Boxes 20-B, 20-H) was introduced into clinical use against tuberculosis in about 1943. However, resistant mutants always survived until newer drugs were developed. Isonicotinylhydrazide (isoniazid) is especially effective in combinations with suitable antibiotics and other drugs.8 The four-drug combination isoniazid, rifampicin (Box 28-A), pyrazinamide, and ethambutol is often used. Nevertheless, bacteria resistant to all of these have developed. 

Ethambutol suppresses the growth of isoniazid- and streptomycin-resistant tubercle bacilli. The most important but not common side effects are optic neuritis, decreased visual acuity, and inability to perceive the color green. 

During the initial phase, isoniazid is always used in combination with one other drug — rifampin, streptomycin, or ethambutol. In advanced or cavitary pulmonary tuberculosis, often three drugs are used — isoniazid, rifampin, and streptomycin or ethambutol. The pharmacological properties of the most often used drugs are summarized in Table 39.1. 

Allium sativum (Liliacease) Bulb Garlic has been used in traditional Chinese and Egyptian medicine for many centuries positive controls included isoniazid, streptomycin, ethambutol, ril ampicin... 

Isoniazid (INH), rifampin, pyrazinamide, ethambutol, and streptomycin are the five first-line agents for treatment of tuberculosis (Table 47-1). Isoniazid and rifampin are the two most active drugs. An isoniazid-rifampin combination administered for 9 months will cure 95-98% of cases of tuberculosis caused by susceptible strains. The addition of pyrazinamide to an isoniazid-rifampin combination for the first 2 months allows the total duration of therapy to be reduced to 6 months without loss of efficacy (Table 47-2). In practice, therapy is initiated with a four-drug regimen of isoniazid, rifampin, pyrazinamide, and either ethambutol or streptomycin until susceptibility of the clinical isolate has been determined. Neither ethambutol nor streptomycin adds substantially to the overall activity of the regimen (ie, the duration of treatment cannot be further reduced if either drug is used), but they do provide additional coverage should the isolate prove to be resistant to isoniazid, rifampin, or both. Unfortunately, such resistance occurs in up to 10% of cases in the United States. Most patients with tuberculosis can be treated entirely as outpatients, with... 

For instance, blurring of vision and diplopia are caused by the use of imipramine, iproniazid, chlorpromazine, thioridazine, and promethazine. Impairment of visual acuity is caused by chlorpropamide, tolbutamide, alcohol, chlorpromazine, phenylbutazone, indomethacin, chloroquine, sulfonamides, ethambutol, chloramphenicol, isonex, clioquinol, quinine, streptomycin, and paraaminosalicylate. Yellow vision (xanthopsia) has been traced to the use of sulfonamides, streptomycin, methaqualone, barbiturates, chlorothiazide,... 

The drugs used to treat TB include capreomycin, cycloserine, ethambutol, isoniazid, pyrazinamide, rifabutin, rifampicin and streptomycin. Resistance is most likely with long courses of treatment of antimicrobial agents and treatment courses are six (or even nine) months long. 

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