Molecule of amantadine
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Symmetrel

Amantadine, 1-aminoadamantane, is an antiviral drug that was approved by the FDA in 1976 for the treatment of influenza type A in adults. The drug has also been demonstrated to help reduce symptoms of Parkinson's disease and drug-induced short-term extrapyramidal syndromes. As an antiparkinsonic it is being prescribed together with L-DOPA when L-DOPA responses decline (probably due to tolerance). Amantadine has been shown to cure SSRI-induced anorgasmia in some people, though not in all people. more...

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It is a derivate of adamantane, like a similar drug rimantadine.

Availability

It is available as a prescription drug as a generic drug and under brand name Symmetrel.

Mechanism of its effects

The mechanism of its antiparkinsonic effect is not fully understood, but it appears to be releasing dopamine from the nerve endings of the brain cells, together with stimulation of norepinephrine response.

The antiviral mechanism seems to be unrelated. The drug interferes with a viral protein, M2 (an ion channel), which is needed for the viral particle to become "uncoated" once it is taken inside the cell by endocytosis.

Misuse

Recently, amantadine is reported to have been used in China poultry farming in an effort to protect the birds against avian flu. In western countries and according to international livestock regulations, amantadine is approved only for use in humans. Chickens in China have received an estimated 2.6 billion doses of amantadine. Avian flu (H5N1) strains in China and southeast Asia are resistant to amantadine, but strains circulating elsewhere seem to be sensitive. If amantadine resistant strains of the virus spread, the drug of choice in an avian flu outbreak will likely be restricted to one of the scarcer and costlier oseltamivir or zanamivir, which work by a different mechanism and are less likely to trigger resistance.

Read more at Wikipedia.org


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Are antibiotics effective in preventing pneumonia for nursing home patients?
From Journal of Family Practice, 12/1/04 by David R. Mouw

* EVIDENCE-BASED ANSWER

Antibiotics should not be used for prophylaxis of pneumonia in nursing homes. We found no studies testing the effectiveness of antibiotics in preventing pneumonia in any population, including persons with predisposing conditions such as influenza. Three measures effectively prevent pneumonia in nursing home patients: influenza vaccination of residents (strength of recommendation [SOR]: B, based on systematic review of homogenous cohort observational studies); influenza vaccination of caregivers (SOR: B, based on individual randomized controlled trial); pneumococcal vaccination of residents (SOR: B, based on randomized, nonblinded clinical trials and consistent case-control studies).

Two other suggested interventions have not been extensively tested: antiviral chemoprophylaxis during an influenza outbreak in the nursing home, and oral hygiene programs for nursing home residents.

* EVIDENCE SUMMARY

Overuse of antibiotics is already a problem in nursing homes. A large portion of bacterial pneumonia in the nursing home population results from aspiration of oropharyngeal bacteria, which is more likely to be drug-resistant if the resident has been on antibiotics. (1) We found no studies that testing antibacterial agents for prevention of pneumonia in nursing home patients. However, 3 measures are clearly helpful in preventing pneumonia in nursing home patients:

1) Influenza vaccination of residents: A meta-analysis of 20 cohort studies showed a 53% efficacy (95% confidence interval [CI], 35-66)--defined as 1 minus the odds ratio--for influenza immunization in preventing pneumonia. (2)

2) Influenza vaccination of caregivers: A cluster randomized trial in British long-term care facilities demonstrated that influenza vaccination of health care workers (61% of 1078 workers) reduced the total nursing home mortality rate (odds ratio [OR]=0.56 [95% CI, 0.4-0.8]) for a drop in mortality rate from 17% to 10% (number needed to treat [NNT] =14.3). (3)

3) Pneumococcal vaccination of residents: This evidence was reviewed in a prior Clinical Inquiry. (4) The evidence comes primarily from 2 clinical trials in which the NNT to prevent 1 episode of pneumonia was about 35.

Two other proposed interventions require further study to evaluate their role in prophylaxis. Antiviral prophylaxis to prevent pneumonia during nursing home outbreaks of influenza has not been evaluated in controlled trials. Observational studies strongly suggest that amantadine, rimantadine, and oseltamivir are all effective in reducing spread of influenza during outbreaks in nursing homes (Table). Oseltamivir acts against influenza B as well as A and has fewer side effects, but it is more expensive. (5,6) Presumably, decreasing the rate of influenza also reduces the rate of subsequent pneumonia.

Oral hygiene programs for nursing home residents may also reduce pneumonia. In a single study, 366 patients in 11 Japanese nursing homes were divided into controls (self-care) and those treated with rigorous oral care (by staff). The intervention group had a relative risk of 0.6 (95% CI, 0.36-0.99; NNT=12.5) for pneumonia over a 2-year period. (7) The NNT for preventing a death by pneumonia was 11 (P<.01). This intriguing result merits follow up in larger groups in US nursing homes to see if this approach is feasible.

* RECOMMENDATIONS FROM OTHERS

There are no recommendations about the use of antibiotic prophylaxis for pneumonia in either the nursing home or in the outpatient settings; however, there are clear recommendations against the overuse of antibiotics. (8)

The CDC Advisory Committee on Immunization Practices (ACIP) recommends:

* annual influenza vaccine for persons residing in nursing homes (9)

* annual influenza vaccine for health care workers in long-term care facilities (9)

* pneumococcal vaccine for persons residing in a nursing home (the schedule for an immunocompetent adult is a single dose, followed by a booster after age 65 if the first dose was before age 65, or after 5 years for persons <65 years with compromised immune status) (10)

* chemoprophylaxis for influenza outbreaks in nursing homes. (11)

* CLINICAL COMMENTARY

Prevention is key for reducing pneumonia mortality

Pneumonia is one of the most common causes of death for nursing home patients. While pneumonia can present with the classic fever, productive cough, and air hunger, it often presents with such nonspecific findings as altered mental status or mild tachypnea, which can significantly delay diagnosis. Additionally, many older adults poorly tolerate the metabolic demands of the disease and become critically ill very rapidly. Thus, prevention remains a key strategy for reducing mortality. Nursing home policies that facilitate vaccination and reduce disease transmission are critically important in this regard.

Jon O. Neher, MD, Valley Medical Center Renton, Wash

REFERENCES

(1.) Yamaya M, Yanai M, Ohrui T, Arai H, Sasaki H. Interventions to prevent pneumonia among older adults. J Am Geriatr Soc 2001; 49:85-90.

(2.) Gross PA, Hermogenes AW, Sacks HS, Lau J, Levandowski RA. The efficacy of influenza vaccine in elderly persons. A meta-analysis and review of the literature. Ann Intern Med 1995; 123:518-527.

(3.) Potter J, Stott DJ, Roberts MA, et al. Influenza vaccination of health care workers in long-term-care hospitals reduces the mortality of elderly patients. J Infect Dis 1997; 175:1-6.

(4.) McCormack O, Meza J, Martin S, Tatum P. Is pneumococcal vaccine effective in nursing home patients? J Fam Pract 2003; 52:150-154.

(5.) Arden NH, Patriarca PA, Fasano MB, et al. The roles of vaccination and amantadine prophylaxis in controlling an outbreak of influenza A (H3N2) in a nursing home. Arch Intern Med 1988; 148:865-868.

(6.) Parker R, Loewen N, Skowronski D. Experience with oseltamivir in the control of a nursing home influenza B outbreak. Can Commun Dis Rep 2001; 27:37-40.

(7.) Yoneyama T, Yoshida M, Ohrui T, et al. Oral care reduces pneumonia in older patients in nursing homes. J Am Geriatr Soc 2002; 50:430-433.

(8.) Strassbaugh LJ, Crossley KB, Nurse BA, Thrupp LD. Antimicrobial resistance in long-term care facilities. Infection Control and Hospital Epidemiology 1996; 17:129-140.

(9.) Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep 1999; 48(RR-4):1-28.

(10.) Prevention of Pneumococcal Disease: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep 1997; 46(RR-8):1-24.

(11.) Bridges CB, Fukuda K, Uyeki TM, Cox NJ, Singleton JA; Centers for Disease Control and Prevention, Advisory Committee on Immunization Practices. Prevention and Control of Influenza. Recommendations of the Advisory Committee on Immunization Practices. MMWR Recomm Rep 2002; 51(RR-3):1-31.

David R. Mouw, MD, PhD, John P. Langlois, MD, MAHEC Family Practice Residency Program, Asheville, NC, Department of Family Medicine, University of North Carolina at Chapel Hill; Linda F. Turner, MSLS, MAHEC Health Sciences Library, Asheville, NC

COPYRIGHT 2004 Dowden Health Media, Inc.
COPYRIGHT 2004 Gale Group

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