Double-blind controlled study of central nervous system side effects of amantadine, rimantadine, and chlorpheniramine. A controlled trial of amantadine and rimantadine in the prophylaxis of influenza A infection. [Controlled study of influenza prophylaxis by VUFB amantadin (author's transl)]. Efficacy and safety of low dosage amantadine hydrochloride as prophylaxis for influenza A. A study of 1-adamantamine hydrochloride during the 1970 Hong Kong influenza epidemic. Therapeutic effectiveness of amantadine hydrochloride in influenza A2--double blind studies. Prevention of Russian influenza by amantadine. Therapeutic effect of 1-adamantanamine hydrochloride in naturally occurring influenza A 2 -Hong Kong infection. A controlled double-blind study. Influenza A prophylaxis with amantadine in a boarding school. Comparative toxicity of amantadine hydrochloride and rimantadine hydrochloride in healthy adults. Therapeutic effects of aerosolized amantadine in naturally acquired infection due to influenza A virus. Treatment of influenza. The therapeutic efficacy of rimantadine HC1 in a naturally occurring influenza A2 outbreak. Administration of amantadine for the prevention of Hong Kong influenza. Oral rimantadine hydrochloride therapy of influenza A virus H3N2 subtype infection in adults. Safety and prophylactic efficacy of low-dose rimantadine in adults during an influenza A epidemic. The prophylactic effectiveness of amantadine hydrochloride in an epidemic of Hong Kong influenza in Leningrad in 1969. Protection of man from natural infection with influenza A2 Hong Kong virus by amantadine: a controlled field trial. Therapeutic efficacy of amantadine HCl and rimantadine HCl in naturally occurring influenza A2 respiratory illness in man. Prophylactic use of amantadine during Hong Kong influenza epidemic. [Therapeutic efficacy of amantadine hydrochloride in patients with epidemic influenza A virus infection]. Prevention of influenza A/USSR/77 (H1N1): an evaluation of the side effects and efficacy of amantadine in recruits at Fort Sam Houston. Comparison of amantadine and rimantadine for prevention of type A (Russian) influenza. Use and withdrawal of amantadine chemoprophylaxis during epidemic influenza A. Reduction in fever and symptoms in young adults with influenza A/Brazil/78 H1N1 infection after treatment with aspirin or amantadine. Amantadine therapy of epidemic influenza a(2) (Hong Kong). Therapeutic effectiveness of amantadine hydrochloride in naturally occurring Hong Kong influenza--double-blind studies. Evaluation of amantadine hydrochloride in the treatment of A2 influenzal disease. Trial of amantadine in epidemic influenza. Amantadine hydrochloride as a prophylactic in respiratory infections. A double-blind investigation of its clinical use and serology. Evaluation of amantadine in the prophylaxis of influenza A (H1N1) virus infection: a controlled field trial among young adults and high-risk patients. Successful treatment of naturally occurring influenza A/USSR/77 H1N1.
A total of 52 healthy, adult volunteers were randomly assigned to five treatment groups to be treated twice daily for 4 days with 100 mg of amantadine, 100 mg of rimantadine, 4 mg of chlorpheniramine or placebo alone, or 100 mg of amantadine in combination with chlorpheniramine. The results of tests measuring performance on tasks of attention, reasoning, and memory were unaffected by treatment. Subjective side effects in recipients of amantadine, rimantadine, and chlorpheniramine were comparable and minimal. Side effects appeared to be enhanced in subjects receiving both amantadine and chlorpheniramine. Four hundred fifty volunteers participated in a placebo-controlled, double-blind, randomized trial of the prophylactic effects of rimantadine and amantadine during an outbreak of influenza A. The subjects received drugs orally at a dose of 100 mg twice a day for six weeks. Influenza-like illness occurred in 41 per cent of the subjects receiving placebo but in only 14 per cent of those receiving rimantadine and 9 per cent of these receiving amantadine (P less than 0.001 for either drug vs. placebo). Laboratory-documented influenza occurred in 21 per cent of placebo recipients, 3 per cent of rimantadine recipients, and 2 per cent of amantadine recipients (P less than 0.001). These findings represent efficacy rates of 85 per cent for rimantadine and 91 per cent for amantadine, as compared with placebo. More recipients of amantadine (13 per cent) than recipients of rimantadine (6 per cent; P less than 0.05) or placebo (4 per cent; P less than 0.01) withdrew from the study because of central-nervous-system side effects. On the basis of this study, rimantadine appears to be the drug of choice for the prophylaxis of influenza A. nan The efficacy and safety of prophylactic low dose amantadine hydrochloride was assessed in two double-blind, placebo-controlled, randomized studies. In a study of 476 subjects aged 18 to 55 years, adverse reactions were not significantly different between the group receiving 100 mg/day amantadine and the placebo group but significantly greater in the group given 200 mg/day (P less than 0.009). The influenza attack rate in this study was too low to assess efficacy. In an experimental challenge study of influenza A/Beth/1/85 in 78 subjects of similar age the prophylactic administration of 50 mg, 100 mg or 200 mg/day doses of amantadine were more effective than placebo in preventing influenza illness (P less than 0.02, 66, 74 and 82% protection, respectively), and in suppressing viral replication (P = 0.02). There was no significant difference between amantadine groups in influenza illness or viral shedding. Compared with the placebo group the 100 and 200 mg amantadine groups showed a significant decrease in infection rate (100 mg: 40% protection: P = 0.012; 200 mg: 32% protection: P = 0.045) whereas the 50 mg group did not (20% protection: P = 0.187). These results suggest that 100 mg/day of amantadine will reduce toxicity but maintain the prophylactic efficacy seen with 200 mg/day. nan nan We tested the effectiveness of amantadine hydrochloride in prevention of illness and infection caused by Russian (h1n1) influenza. The trial lasted seven weeks and was double-blind and placebo controlled. The dosage used was 200 mg daily. Efficacy in prevention of serologically confirmed clinical influenza was 70.7%. Efficacy in prevention of infection, symptomatic or asymptomatic, was 39.4%. Side effects seen were all mild, began within two days of the start of the trial, and terminated rapidly on cessation of prophylaxis. The withdrawal rate attributable to use of amantadine was 6.2%. Those who continued to receive prophylaxis for the remainder of the trial did not exhibit excess side effects. It is concluded that amantadine is safe and effective in prophylaxis of H1N1 strains, as has been shown previously for other subtypes of A influenza. nan In a boarding school for boys, where routine influenza vaccination is carried out annually, 267 boys were given amantadine (100 mg daily) and 269 received no specific treatment during an influenza A (H1N1) outbreak. 3 boys receiving amantadine and 29 boys receiving no medication had laboratory-proven influenza A. There are circumstances when the prophylactic use of amantadine may be justified for the control of influenza A outbreaks in boarding schools and other institutions where high attack-rates are experienced. The relative toxicities of amantadine and rimantadine were compared in a double-blind, placebo-controlled study involving healthy adults. In separate studies, drugs were administered at a dosage of 200 mg/day (52 volunteers) or 300 mg/day (196 volunteers) for 4.5 days. Both drugs were well tolerated at the lower dosage. At 300 mg/day amantadine recipients had a greater frequency and severity of central nervous system (nervousness, lightheadedness, difficulty concentrating) and sleep (insomnia, fatigue) complaints compared with rimantadine or placebo recipients. Amantadine recipients also performed less well on an objective test measuring sustained attention and problem-solving ability. Both amantadine and rimantadine recipients reported adverse gastrointestinal symptoms more often than placebo recipients. Because of better tolerance at higher dosage, rimantadine offers more promise than amantadine for treatment of influenza A virus infections. The effect of small-particle aerosol therapy with amantadine was assessed in a randomized, double-blind study of 20 patients with naturally acquired influenza A virus infection. Aerosol treatments of 20 min with either distilled water or with amantadine hydrochloride (1.0 g/100 ml of distilled water) were given three times a day for four days. The amantadine-treated patients experienced a significantly more rapid resolution of clinical signs and symptoms when compared with placebo-treated patients. The resolution of fever was similar for both groups. Aerosol delivery of amantadine did not affect the frequency of viral isolation from upper respiratory tract secretions but was associated with a trend toward reduced quantity of viral shedding. Serial pulmonary function tests found no important differences between the groups. Amantadine-treated patients experienced a greater frequency of mild local side effects (rhinorrhea, nasal irritation) during aerosol exposures, but aerosol treatments did not cause any apparent decline in pulmonary function. nan The prophylactic effectiveness of amantadine against A2/Hong Kong influenza was investigated in the course of a double-blind trial in Braşov, Romania, during an epidemic due to the Hong Kong virus that started there in March 1969.Altogether 215 subjects were included in the trial; 112 received 100 mg of amantadine twice daily for 20 days and the remaining 103 received inert placebo tablets. Of the amantadine-treated group, 2 had clinical symptoms diagnosed as influenza (1 of these was a doubtful diagnosis), whereas 20 (1 doubtful) of the placebo group had such symptoms. No case with both clinical symptoms and serologically confirmed influenza (>/=4-fold increase in haemagglutination-inhibition titre) occurred among 77 amantadine-treated subjects for whom paired sera were available but there were 13 such cases among the 74 placebo subjects with paired sera. These differences are statistically highly significant. No serious side-effects were recorded.The authors conclude that amantadine was highly effective in preventing overt disease and discuss indications that suggest that it did not interfere with the development of immunity in persons treated during the incubation period. In a randomized, double-blind trial involving patients with uncomplicated influenza A H3N2 subtype virus infection, rimantadine treatment (200 mg/day for 5 days) was associated with significant reductions in nasal secretion viral titers (days 2 through 4), maximal temperature (days 2 and 3), time until defervescence (mean, 37 h shorter), and systemic symptoms compared with placebo treatment. A placebo-controlled, double-blind study to evaluate the safety and prophylactic efficacy of a low dose (100 mg) of rimantadine hydrochloride against naturally occurring influenza in adults was conducted at two sites. After the onset of the influenza season, volunteers (ages, 18 to 55 years) were assigned randomly to receive rimantadine or placebo daily. Subjects were monitored for adverse effects and evidence of influenza virus infection weekly for six weeks. Only 10 (8.7%) of 114 rimantadine recipients and 5 (4.4%) of 114 placebo control recipients reported one or more mild to moderate adverse symptoms, most of which were related to the gastrointestinal or central nervous system. Compared with placebo, low-dose rimantadine was highly effective in the prevention of influenza A virus infection (20 of 110 versus 7 of 112 participants; P less than 0.01) and influenza illness (7 of 110 versus 1 of 112 participants; P = 0.04). Influenza A/Leningrad/87-like (H3N2) virus was recovered from the nasopharynxes of only five placebo recipients. These findings indicate that low-dose rimantadine is well tolerated and highly effective for the prevention of influenza A illness in healthy adults. The effectiveness of amantadine hydrochloride as a prophylactic against influenza was studied during an epidemic caused by viruses related to influenza A2/Hong Kong/1968 variants in Leningrad, USSR, early in 1969. In all, 8169 subjects, assigned to amantadine-dosed, placebo-dosed, internal control and external control groups, were assessed. The index of effectiveness of the prophylactic medication, based on clinical diagnosis, in subjects who took amantadine regularly was 1.95. When the clinical diagnoses were confirmed serologically the index of effectiveness for the amantadine compared with the placebo group increased to 2.7. A comparison of the medicated group with the non-medicated, non-isolated internal control group showed an index of effectiveness of 5.34. A daily dose of 100 mg of amantadine was associated with an increase of 1.14% in complaints of sleep disturbances but these had no effect on the working capacity of subjects. Prophylactic administration of amantadine in doses of 100 mg. twice a day offered statistically significant protection against influenza A2 infection in a double-blind field trial involving 391 medical student volunteers during the influenza A2 Hong Kong epidemic in Helsinki in the winter of 1969. Serologically verified influenza, as measured by complement fixation and/or haemagglutination inhibition, occurred in 27 out of 192 students in the amantadine group against 57 out of 199 in the placebo group, giving a protection rate of 52%. nan nan A virus infection was studied using half of the normal oral dose of amantadine hydrochloride-100 mg/d instead of 200 mg/d. The patients in this study, who visited the clinics during January and February 1999, were confirmed within 48 hours to have influenza A virus infections by the Directigen FluA test. Using a quasi-randomized controlled trial, 26 patients were treated with amantadine hydrochloride in addition to the usual medication, while 23 were treated with only the ordinary medication. There were no significant differences in the mean age, 35.6 years old, or in clinical features between the two groups. The period of fever over 38 degrees C in the amantadine treated group was 1 day while that in the control group was 1.7 days, which shows a significant difference (p = 0.049). There was no significant difference in the duration of aching, such as arthralgia, or of general fatigue. There was no significant difference in the appearance of subsequent new symptoms after the onset of influenza A virus infection. In conclusion, it is expected that oral amantadine hydrochloride, 100 mg/d, together with the ordinary medication, will reduce the duration of the period of fever over 38 degrees C. nan The efficacies of 200 mg of daily doses of amantadine and of rimantadine for prevention of infection and illness due to influenza A/USSR/77 (H1N1) virus were compared in a double-blind, placebo-controlled study on a college campus. Frequencies of symptoms that might have been side effects of the drugs were not significantly different from those in placebo recipients. Analyses indicated that the trial was initiated late in the epidemic and that an age-related protective effect against A/USSR virus existed; seroconversion frequencies were 52/139 (37%) among 18-19-year-olds, 33/130 (25%) among 20-21-year-olds, and 5/39 (12.8%) among 22-24-year-olds. Among initially antibody-negative (less than 1 : 4 in complement fixing and neutralizing tests and less than 1 : 8 in hemagglutination inhibition tests) 18-19-year-old students, amantadine was associated with significantly fewer seroconversions (P = 0.01) and both less infection and milder illness than occurred in placebo recipients (P less than 0.05). Although rimantadine was not accompanied by reduction in frequency of seroconversions in the same age group, illness frequency and severity among seroconverters were significantly reduced when compared to placebo recipients (P less than 0.01). Amantadine and rimantadine appear suitable for use in young adults. Although other studies have suggested greater effectiveness of rimantadine than of amantadine against influenza, no evidence for this was seen in the present study which used both drugs at the same dose. A controlled investigation of chemoprophylaxis with amantadine hydrochloride during an epidemic of influenza A was performed in nonimmune students. Illness was significantly decreased and serologic evidence of infection reduced by treatment. During the post-treatment period, while influenza was still prevalent, an accelerated rate of infection occurred among persons previously protected by chemotherapy. When used, chemoprophylaxis should be continued until influenza is no longer prevalent or, preferably, should be combined with vaccine administration to ensure protection after treatment. During an outbreak of influenza A/Brazil/78 H1N1 infection, 47 volunteers with clinical and virological influenza of less than 2 days duration were treated in a randomized double-blind fashion for 5 days with 100 or 200 mg of amantadine daily or with 3.25 g of aspirin daily. The aspirin treatment group defervesced more rapidly (10.3 h versus 21.5 h and 23.6 h; P less than 0.01), but by the second daily follow-up visit, both groups of amantadine recipients exhibited greater symptomatic improvement. Bothersome side effects resulted in discontinuation of therapy by 35% of the aspirin treatment group but only 3% of the amantadine treatment group (P less than 0.05). Individuals who present to a physician during an influenza A epidemic with characteristic symptoms will experience symptomatic benefit from amantadine treatment, with negligible toxicity. In a double-blind comparison of the therapeutic effect of amantadine in a natural outbreak of Hong Kong influenza in January 1969 near Houston, Texas, the decrease in titers of virus in throat swabs from 12 treated patients during the first 10 hr of treatment was appreciably greater than similar titers of virus from 16 untreated patients (P = 0.06). The titer of shed virus decreased significantly more rapidly (P < 0.05) among amantadine-treated patients ill more than 48 hr before treatment than among five control patients who had been ill more than 48 hr. Cough, sore throat, and nasal obstruction cleared more rapidly in treated patients (P < 0.05), and decline of fever in 6 treated patients sick for less than 48 hr before treatment was more rapid than among 13 untreated patients who had been ill for less than 48 hr. These findings are considered to be consistent with a limited therapeutic effect of the drug. nan Amantadine hydrochloride is the first drug to show promise as a practical anti-influenza agent. Several studies demonstrating a prophylactic effect in volunteers with induced A2 disease as well as in patients during A2 outbreaks have created the impetus for therapeutic trials. The widespread A2 influenza epidemic that occurred early in 1968 provided the opportunity for therapeutic evaluation in the USA.A total of 197 prison inmates with proven influenza agreed to participate in the 10-day double-blind evaluation of amantadine (100 mg, twice daily). Onset of therapy was approximately 20 hours after first subjective awareness of illness.Assessment of drug effectiveness was based on rapidity of resolution of illness. There was a significant increase in the number of drug-treated as against placebo patients in the "rapid resolver" group whereas individuals receiving placebo dominated the "slow resolver" group. Analysis of febrile responses indicated that amantadine-treated patients had significantly more rapid defervescence. Virus isolation studies revealed etiologically related virus in 90% of all volunteers during the first 5 days of therapy. It was apparent that clinical improvement was not correlated with disappearance of the virus. Nevertheless, the trials conducted during the influenza season of early 1968 indicated the therapeutic effect of amantadine hydrochloride. Administration of 100 mg, twice daily, for 10 days did not cause any adverse effects. nan nan The usefulness of amantadine in the protection of humans against influenza A (H1N1) virus was evaluated in a double-blind field trial with 555 volunteers in Finland in the winter of 1978. Three populations--patients in a general hospital, adults in a home for the aged, and two groups of military conscripts--were chosen. Epidemic influenza occurred only in the two groups of conscripts: the incidence of serologically verified influenza was 66% and 83% in the groups that received placebo and 43% and 51% in the groups that received amantadine, giving protection rates of 36% (P = 0.05) and 39% (P = 0.001). The evaluation of the effect of amantadine on the occurrence of illness was obscured by concomitant adenoviral infections that caused influenza-like symptoms. No clear difference in the occurrences of side effects was observed between the placebo and amantadine-treated groups; however, a significantly greater number of participants who took 200 mg of amantadine/day (16.9%) stopped medication during the trial as compared with the placebo groups (7.6%) (P < 0.02). Forty-five university students with proved influenza A/USSR/77 H1N1 infection were randomly treated with either amantadine hydrochloride (14 students), rimantadine hydrochloride (19 students), or placebo (12 students). By 48 hours after initiation of therapy, amantadine and rimantadine recipients had significantly less fever and greater improvement compared with subjects given the placebo. Minor reversible CNS side effects at the end of the five-day course of therapy were observed in one third of the amantadine-treated subjects. However, both amantadine and rimantadine recipients returned to classes earlier and shed smaller amounts of virus than placebo recipients. Thus, both drugs exerted a notable therapeutic effect. Hence, during an influenza outbreak, five days of empirical therapy with amantadine or rimantadine for persons with an influenza-like syndrome should ameliorate clinical symptoms and might decrease spread of virus.
Amantadine and rimantadine have comparable efficacy and effectiveness in relieving or treating symptoms of influenza A in healthy adults, although rimantadine induces fewer adverse effects than amantadine. The effectiveness of both drugs in interrupting transmission is probably low. Resistance of influenza viruses to amantadine is a serious worldwide problem as shown by recent virological surveillances. Both drugs have adverse gastrointestinal (stomach and gut) effects, but amantadine can also have serious effects on the nervous system. They should only be used in an emergency when all other measures fail.