***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Codeine is generally accepted as the st and ard antitussive against which new antitussive medications are compared . This presents a problem because the support for codeine 's antitussive activity comes from studies on cough in animals , and chronic and induced cough models in man , whereas antitussives are almost exclusively used for the treatment of cough associated with acute upper respiratory tract infection ( URTI ) . The aims of this study were twofold . Firstly , to study the antitussive efficacy of codeine in cough associated with URTI and , secondly , to vali date a sound meter as tool for quantifying cough . The efficacy of codeine was assessed in a double-blind , stratified , placebo-controlled , parallel-group , clinical trial using three different measures of cough : cough sound-pressure levels ( CSPLs ) measured on a sound meter ; subjective scores of cough severity ; and cough frequency recorded by means of a microphone  connected to an ink-pen recorder .  A group of 82 subjects ( 51 females and 31 males ; mean age 23.5 years , range 18 - 46 years ) with cough owing to acute URTI were included in the study . The study took place on two separate study days . On study day 1 cough measurements were made before and 90 min after treatment with a single dose of either 50 mg codeine or matched placebo in capsule form . The same three measures of cough were repeated 2 - 5 days later ( study day 2 ) . On study day 1 a highly significant ( P < 0.0001 ) decrease in all three measures of cough was found after treatment with both placebo and codeine yet there was no significant difference between the treatment groups . A highly significant ( P < 0.0001 ) decrease in the three measures of cough was also found between days 1 and 2 . The results demonstrate that codeine is no more effective than placebo in reducing cough associated with acute URTI , as measured by CSPLs , cough frequency or subjective symptom scores . This result might be explained on the basis of two central pathways for cough ; a reflex pathway via the brain-stem which is sensitive to codeine and a voluntary pathway via the cortex which is unaffected by codeine . The results also demonstrate that the sound-level meter appears to be a potentially useful investigative tool for the assessment of cough and antitussive efficacy To determine whether the cough of the common cold arises from upper respiratory stimuli and whether antihistamine-decongestant therapy is an effective treatment for this cough , we prospect ively evaluated volunteers with uncomplicated common colds in a r and omized , double-blind , placebo-controlled study . After completing a st and ardized question naire and undergoing a physical examination , throat-culturing , and pulmonary function testing , subjects took the active drug or identical-appearing placebo for 7 days while they kept a diary in which they ranked the severity of 17 symptoms for 14 days . Pulmonary function testing was repeated , on average , on Days 4 , 8 , and 14 . Forty-six percent of the variation in cough severity could be explained by throat-clearing and 47 % of the variation in throat-clearing severity by postnasal drip . FIF50 % , the only physiologic parameter that significantly correlated with cough , rose as cough severity fell . Antihistamine-decongestant therapy reduced postnasal drip and significantly decreased the severity of cough , nasal obstruction , nasal discharge , and throat-clearing during the first few days of the common cold . In addition , cough was 20 to 30 % less prevalent in the active drug group within 3 days of starting therapy . We conclude that the cough of the common cold arose from upper respiratory tract stimuli and that cough and other cardinal symptoms of the common cold were reduced with antihistamine-decongestant therapy when these symptoms were at their worst The efficacy of guaifenesin in reducing cough frequency in young adults with acute respiratory disease was evaluated by both an objective cough counting system and a question naire . A guaifenesin cough preparation and the syrup vehicle were administered in a double-blind manner . Coughs were recorded on tape over a 24-hour baseline evaluation period and a 36-hour treatment period for 42 patients . A pronounced diurnal variation in cough frequency was observed . The evaluation of efficacy was based upon comparisons between equivalent six-hour time periods of successive days . No antitussive effect of guaifenesin was demonstrated . The question naire was administered to 65 patients , including the 42 whose coughs were recorded . Of 26 patients with productive cough receiving guaifenesin  , 25 ( 96 percent ) reported a decrease in sputum thickness compared to 13 ( 54 percent ) of 24 patients receiving the vehicle ( p = 0.01 , Fisher exact test ) . Twenty-three of 26 ( 88 percent ) patients receiving guaifenesin also reported reduction in sputum quantity compared to 15 of 24 ( 62.5 percent ) receiving the vehicle ( p = 0.07 , Fisher exact test ) . The diurnal variation in cough frequency measured by the tape recording was not apparent from the subjective cough frequency estimates obtained by the question naire A double blind vs placebo study was carried out to study the effect of letosteine on the symptoms and clinical course of paediatric patients suffering from acute febrile bronchitis . Forty children were recruited for the research : 20 were treated with letosteine in a dose of 25 mg x 3 g/die and 20 with placebo ; treatment lasted 10 days . The following parameters were assessed during the trial : body temperature , cough , thoracic objectivity , respiratory function indices . The results of the study show that in the letosteine treated group there is a statistically significant decrease in fever , a favourable evolution of thoracic objectivity and an improvement in certain respiratory function parameters ( MEF 75 , PEF ) . It is concluded that treatment with letosteine leads to a significant increase in the rate of regression of thoracic symptomatology and a faster , more substantial reduction in fever in children suffering from acute bronchitis . This is probably the result of drug action on mucus viscosity , restoring optimal mucociliary clearance , and through action fostering the penetration of antibacterial substances into the mucus Codeine is often used as a st and ard 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 We tested the hypothesis that antihistamine-decongestant combinations cause no clinical ly significant relief of the symptoms of upper respiratory tract infections in young children by r and omly assigning 96 children to one of three treatment groups : antihistamine-decongestant , placebo , and no treatment . There were no differences among the three study groups in the proportion of children considered " better " overall by the parent 48 hours after the initial assessment ( drug , 67 % ; placebo , 71 % ; no treatment , 57 % ; p = 0.53 ) . There were no differences among groups in individual or composite symptom score changes . Two thirds of parents whose children were eligible for the drug trial believed that their child needed medicine for cold symptoms . In the proportion of parents believing that their child needed medicine , there was no difference between those who consented to participate and those who refused . Parents who wanted medicine at the initial visit reported more improvement at follow-up , regardless of whether the child received drug , placebo , or no treatment . We conclude that there is no clinical ly significant improvement in symptoms of upper respiratory tract infection , including no significant placebo effect , in young children for whom an  antihistamine-decongestant  is prescribed The efficacy of an antitussive-beta 2-sympathomimetic combination ( dextromethorphan-salbutamol ) was compared with that of a plain antitussive ( dextromethorphan ) and a placebo in a double-blind trial in 108 out- patients with cough associated with acute respiratory infection . The dextromethorphan-salbutamol combination was superior to dextromethorphan or placebo in the suppression of cough at night , although a spontaneous improvement occurred in all treatment groups during the 4-day treatment period . No statistically significant differences between the treatments were shown in the symptom scores for the cough frequency and severity during the day , sputum quantity or ease of expectoration . A significant improvement in cough during the day was observed in all treatment groups . The results suggest that the use of antitussives is usually unnecessary ; the only indication might be symptomatic relief , especially at night . An antitussive combined with a beta 2-sympathomimetic might be the most effective treatment in this type of cough The antitussive efficacy and tolerability of dropropizine and of its enantiomer levodropropizine were evaluated in children with non-productive cough ; 258 were evaluable for tolerability and 254 for efficacy . Patients r and omly received either 1 mg/kg dropropizine or 2 mg/kg levodropropizine orally , three times daily for 3 days . There were statistically significant decreases in the frequency of coughing spells and nocturnal awakenings after both levodropropizine and dropropizine treatments ( P < 0.001 ) . Gastrointestinal symptoms were mild in the two groups ; somnolence was twice as frequent in the dropropizine group ( 10.3 % vs 5.3 % ) and the difference is clinical ly relevant , though not statistically significant . Levodropropizine is as effective as an antitussive as dropropizine , but appears to carry a lower risk of daytime somnolence To test the hypothesis that codeine and dextromethorphan are effective in alleviating the symptoms of  acute cough  , we conducted a r and omized , controlled trial . Eligible patients were children 18 months to 12 years of age , seen in private pediatric practice s , with significant night cough of less than 14 days ' duration . Study patients were r and omly selected to receive codeine , dextromethorphan , or placebo at bedtime for 3 consecutive nights . Outcomes were assessed by the use of a parent question naire rating the severity of symptoms at the initiation of therapy , and after each night of the study . Every patient had a cough score ( range 0 to 4 ) and composite symptom score ( range 0 to 9 ) computed for each day of the study . One hundred forty-one doses of study medication were evaluated in 49 patients , including 13 children receiving placebo , 19 dextromethorphan , and 17 codeine .  Mean cough and composite symptom scores decreased in each of the three treatment groups on each day of the study ; there were no significant differences . Regression analysis , with reduction in cough score as the outcome of interest , showed that neither dextromethorphan nor codeine was significantly more effective than placebo ( p = 0.41 and 0.70 , respectively ) . Reduction in cough score was positively correlated with the severity of cough at the start of treatment ( p = 0.007 ) . Our data suggest that , in the doses used , neither codeine nor dextromethorphan is superior to placebo in treating night cough in children OTHER investigators,1 - 6utilizing various techniques , have attempted to determine objective ly the response of cough  to antitussive medication .  Volunteer adult patients were used almost exclusively in those studies . The techniques employed have consisted of induction of cough by artificial means , such as successive inhalations of an irritant aerosol , and of assay of antitussive activity of cough medications based on reduction in number of coughs provoked by the irritant . The irritant usually was citric acid or acetylcholine . While the data obtained gave a valid indication of a cough-suppressing effect , experimental production of cough by chemical or mechanical irritants is subject to certain limitations and criticisms . First , the healthy volunteer after repeated exposure develops a tolerance to the irritant , especially when the latter is citric acid . Second , the frequency and intensity of artificially induced cough vary with the concentration of the irritant and the interval between challenges . Third , the artificially induced One hundred and thirty out- patients , affected by acute and chronic cough caused by upper respiratory tract inflammation , took part in two clinical studies aim ed at evaluating the efficacy and tolerability of glaucine , a new antitussive agent . The first study involved 90 patients in a double-blind comparative trial of glaucine and codeine :  both treatments were administered as a syrup at a dosage of 30 mg 3-times daily for 7 days . The cough suppressant effect of the two treatments was checked by the physician and the patient using a 4-point scale ( from absent to severe ) , and by the patient using a visual analogue scale . Mean scores of the physician 's evaluation decreased from 3.0 to 1.10 after codeine and from 3.0 to 0.47 after glaucine ( p less than 0.001 between treatments ) 
    Output:
    
2 .
Antihistamines were no more effective than placebo in relieving cough symptoms .
REVIEW ERS ' CONCLUSIONS There is no good evidence for or against the effectiveness of OTC medicines in acute cough .
More evidence about the effectiveness of OTC cough preparations would be helpful , as identification of effective self-care treatments may help reduce the burden of days lost at work due to acute cough as well as the number of consultations in primary care .
Identification of ineffective preparations could avoid costs for consumers and health care providers