Objective. To investigate the safety (risk) and efficacy (benefit) of Echinacea purpurea extract in the prevention of common cold episodes in a large population over a 4-month period. Methods. 755 healthy subjects were allocated to receive either an alcohol extract from freshly harvested E. purpurea (95% herba and 5% root) or placebo. Participants were required to record adverse events and to rate cold-related issues in a diary throughout the investigation period. Nasal secretions were sampled at acute colds and screened for viruses. Results. A total of 293 adverse events occurred with Echinacea and 306 with placebo treatment. Nine and 10% of participants experienced adverse events, which were at least possibly related to the study drug (adverse drug reactions). Thus, the safety of Echinacea was noninferior to placebo. Echinacea reduced the total number of cold episodes, cumulated episode days within the group, and pain-killer medicated episodes. Echinacea inhibited virally confirmed colds and especially prevented enveloped virus infections (P < 0.05). Echinacea showed maximal effects on recurrent infections, and preventive effects increased with therapy compliance and adherence to the protocol. Conclusions. Compliant prophylactic intake of E. purpurea over a 4-month period appeared to provide a positive risk to benefit ratio.

The aim of the present study was to investigate the voluntary suppression of cough in response to capsaicin inhalation in healthy volunteers, and to determine if the dose-response curve to capsaicin was significantly altered when volunteers were asked to suppress their cough response. The quantification of the degree of voluntary suppression of induced cough could provide a new methodology for screening antitussive agents as antitussives may act by influencing voluntary control of cough. Cough was induced by inhalation of capsaicin. Two challenges were given 5 min apart, each comprising five ascending concentrations of capsaicin (1 x 10(-5) M-3.33 x 10(-4) M). During one of these challenges the volunteer was allowed to cough when required, and during the other they were asked to suppress cough. These two conditions were given in random order. The cough response was recorded by means of a microphone with the integrated sound trace displayed on a chart recorder. A dose-response relationship was obtained on administration of ascending concentrations of capsaicin. In the non-suppressed challenge 23/24 subjects coughed on inhalation of capsaicin (3.33 x 10(-4) M) with a mean number of coughs of 2.92 +/- 0.34, whereas in the suppressed challenge only 3/24 subjects coughed with a mean number of coughs of 0.29 +/- 0.18 (P < 0.001). These results demonstrate that cough induced by inhalation of capsaicin can be voluntarily suppressed. The mechanism of voluntary suppression of cough is discussed in relation to capsaicin challenge and the screening of antitussive medications.

The effects of oral administration of a lozenge containing 11 mg (-)-menthol on nasal resistance to airflow (NAR) and nasal sensation of airflow in 62 subjects suffering from nasal congestion associated with naturally acquired common cold infection have been studied. NAR was measured by posterior rhinomanometry and nasal sensation of airflow by means of a visual analogue scale (VAS). The effects of the lozenge were compared with a candy placebo lozenge in a double blind randomized trial. NAR showed a significant increase (P less than 0.05) in both the menthol and placebo groups over the 2 h experiment with no difference between the groups at any time. The VAS scores showed significant changes of subjective improvement in nasal sensation of airflow (P less than 0.001) in the menthol-treated group 10 min after dosing whereas the placebo group showed no change. It is concluded that dosing with 11 mg menthol in subjects with common cold has no effect on NAR as measured by posterior rhinomanometry but causes a marked change in nasal sensation of airflow with a subjective sensation of nasal decongestion.

Codeine is often used as a standard antitussive against which new antitussives are compared. However there is little information available about the effects of codeine on cough associated with upper respiratory tract infection. The present study investigated the effects of codeine syrup B.P. (30 mg/10 ml, q.d.s.) or syrup vehicle on cough frequency and the subjective severity of cough during a 3-h laboratory phase and a 4-day home phase of treatment. Cough frequency and subjective scores of cough severity were significantly decreased during the 3-h laboratory phase but at no time point was there a significant difference between the codeine- and placebo-treated groups. The results of the 4-day home phase diary were similar to those of the laboratory phase as at no time point was there a significant difference between the mean scores for the codeine- and placebo-treated groups. The results indicate that codeine, either as a single 30-mg dose or in a total daily dose of 120 mg, is no more effective than the syrup vehicle in controlling cough associated with acute upper respiratory tract infection.

Dextromethorphan is one of the most widely used antitussives for the treatment of cough associated with acute upper respiratory tract infection. However, there is very little data to support the efficacy of dextromethorphan in this disease state. This aim of this study was to obtain more information about the efficacy of a single dose of 30 mg dextromethorphan in the treatment of cough associated with acute upper respiratory tract infection. The study was a double-blind, stratified, randomized and parallel group design. Both objective and subjective measurements of cough were recorded over 10-min recording periods in a quiet room before (baseline) and at 90, 135 and 180 min after treatment. Forty-three patients (30 females and 13 males), mean age 22.9 years (range 18-46 years), with acute dry or slightly productive cough and otherwise healthy were included in the study. Patients were randomized to placebo treatment (n = 22) and dextromethorphan treatment (n=21). The results showed similar trends in both treatment groups with statistically significant reductions (P < 0.05) in cough sound pressure level (CSPL), cough frequency (CF) and subjective scores for cough severity within treatment groups but little difference between the treatment groups during the study period. The only statistically significant difference between treatment groups was for the mean CSPL changes from baseline to 90 min (P=0.019). There was a significant positive correlation between CSPL and CF (r = 0.752, P= 0.000) for changes in cough measurements from baseline to 90 min after treatment and this indicates that CSPL may be a useful measure of cough severity. This study provides very little if any support for clinically significant antitussive activity of a single 30 mg dose of dextromethorphan in patients with cough associated with acute upper respiratory tract infection.