Comparison of the effects of single doses of the new H1-receptor antagonists loratadine and terfenadine versus placebo in children

Antihistamines for the common cold

BACKGROUND

The common cold is an upper respiratory tract infection, most commonly caused by a rhinovirus. It affects people of all age groups and although in most cases it is self limiting, the common cold still causes significant morbidity. Antihistamines are commonly offered over the counter to relieve symptoms for patients affected by the common cold, however there is not much evidence of their efficacy.

OBJECTIVES

To assess the effects of antihistamines on the common cold.

SEARCH METHODS

We searched CENTRAL (2015, Issue 6), MEDLINE (1948 to July week 4, 2015), EMBASE (2010 to August 2015), CINAHL (1981 to August 2015), LILACS (1982 to August 2015) and Biosis Previews (1985 to August 2015).

SELECTION CRITERIA

We selected randomised controlled trials (RCTs) using antihistamines as monotherapy for the common cold. We excluded any studies with combination therapy or using antihistamines in patients with an allergic component in their illness.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. We collected adverse effects information from the included trials.

MAIN RESULTS

We included 18 RCTs, which were reported in 17 publications (one publication reports on two trials) with 4342 participants (of which 212 were children) suffering from the common cold, both naturally occurring and experimentally induced. The interventions consisted of an antihistamine as monotherapy compared with placebo. In adults there was a short-term beneficial effect of antihistamines on severity of overall symptoms: on day one or two of treatment 45% had a beneficial effect with antihistamines versus 38% with placebo (odds ratio (OR) 0.74, 95% confidence interval (CI) 0.60 to 0.92). However, there was no difference between antihistamines and placebo in the mid term (three to four days) to long term (six to 10 days). When evaluating individual symptoms such as nasal congestion, rhinorrhoea and sneezing, there was some beneficial effect of the sedating antihistamines compared to placebo (e.g. rhinorrhoea on day three: mean difference (MD) -0.23, 95% CI -0.39 to -0.06 on a four- or five-point severity scale; sneezing on day three: MD -0.35, 95% CI -0.49 to -0.20 on a four-point severity scale), but this effect is clinically non-significant. Adverse events such as sedation were more commonly reported with sedating antihistamines although the differences were not statistically significant. Only two trials included children and the results were conflicting. The majority of the trials had a low risk of bias although some lacked sufficient trial quality information.

AUTHORS' CONCLUSIONS

Antihistamines have a limited short-term (days one and two of treatment) beneficial effect on severity of overall symptoms but not in the mid to long term. There is no clinically significant effect on nasal obstruction, rhinorrhoea or sneezing. Although side effects are more common with sedating antihistamines, the difference is not statistically significant. There is no evidence of effectiveness of antihistamines in children.

Clinical pharmacology of the H1-receptor antagonists cetirizine and loratadine in children

H1-receptor antagonists are widely used in children but are not as well-studied in children as they are in adults. Our objective was to determine the onset and duration of action and the relative potency of the H1-receptor antagonists cetirizine and loratadine in children. We performed a prospective, randomized, placebo-controlled, double-blind, crossover, single-dose study of cetirizine and loratadine using suppression of the histamine-induced wheal and flare as the primary outcome. In 15 allergic children, mean age 9 years, compared with baseline, cetirizine (10 mg) suppressed the wheals and flares significantly from 0.25 to 24 h, achieving nearly 100% of flare suppression from 2 to 24 h, inclusive, and loratadine (10 mg) suppressed the wheals and flares significantly from 0.75 to 24 h, inclusive. Cetirizine suppressed the wheals and flares significantly more than loratadine from 0.25 to 1 h, inclusive, and at 0.5, 1, 2, 3, 5, 6, 7, and 24 h, respectively. Placebo also suppressed the wheal and flare significantly at some assessment times. Cetirizine and loratadine both have excellent antihistaminic activity in children, with a rapid onset of action and a 24-h duration of action in this population.

Adverse central nervous system effects of older antihistamines in children

Although older, potentially sedating, "first-generation" antihistamines (H1-receptor antagonists) are commonly used in childhood, their central nervous system (CNS) effects have not been well-documented in young subjects. We hypothesized that diphenhydramine and hydroxyzine would affect CNS function adversely in this population. Our objective was to evaluate the effects of these medications on central and peripheral histamine H1-receptors in children. Fifteen subjects with allergic rhinitis were tested before and 2-2.5 h after administration of diphenhydramine, hydroxyzine, or placebo in a double-blind, single-dose, three-way crossover study. Impairment of cognitive processing was assessed objectively by the latency of the P300 event-related potential (P300). Somnolence was assessed subjectively by a visual analog scale. Peripheral H1-blockade was assessed by suppression of the histamine-induced wheals and flares. At the central (Cz) and frontal (Fz) electrodes, diphenhydramine and hydroxyzine increased the P300 latency significantly (P < 0.05) compared to baseline. Hydroxyzine increased somnolence, as recorded on the visual analog scale, significantly compared to baseline (P < 0.05), with a similar trend for diphenhydramine (P = 0.07). Both antihistamines reduced histamine-induced wheals and flares significantly compared to baseline and compared to placebo. In children, diphenhydramine and hydroxyzine are effective H1-receptor antagonists, but both these medications cause CNS dysfunction, as evidenced by increased P300 latency, a measure of cognitive function, and by increased subjective somnolence.

Loratadine. A reappraisal of its pharmacological properties and therapeutic use in allergic disorders

Loratadine is a long-acting antihistamine agent, exhibiting partial selectivity for peripheral histamine H1-receptors. To date, loratadine has been evaluated in allergic rhinitis, urticaria and, to a limited extent, in asthma. In several large controlled comparative clinical studies, loratadine was superior to placebo, faster acting than astemizole and as effective as azatadine, cetirizine, chlorpheniramine (chlorphenamine), clemastine, hydroxyzine, mequitazine and terfenadine in patients with allergic rhinitis and chronic urticaria. The clinical effectiveness of loratadine in asthma is at present unclear. Loratadine is well tolerated. At dosages of 10 mg daily, commonly reported adverse events were somnolence, fatigue and headache. Sedation occurred less frequently with loratadine than with azatadine, cetirizine, chlorpheniramine, clemastine and mequitazine. Serious ventricular arrhythmias, as reported with some other second generation histamine H1-receptor antagonists, have not been observed with loratadine to date. Thus, loratadine, with its attributes of once daily administration, fast onset of action and essentially nonsedating properties, would appear to be an appropriate first-line agent for the treatment of allergic rhinitis or urticaria.

Benefit/risk ratio of the antihistamines (H1-receptor antagonists) terfenadine and chlorpheniramine in children

There are few objective studies of the benefit/risk ratio of H1-receptor antagonists in children. We hypothesized that terfenadine would provide as effective peripheral H1 blockade as chlorpheniramine in young patients, but would cause less central nervous system dysfunction. We tested this hypothesis with epicutaneous histamine tests to monitor peripheral H1 blockade, P300-event-related potentials as a measure of cognitive processing, and a visual analog scale for somnolence, in a double-blind, single-dose, placebo-controlled, three-way crossover study in 15 children with allergic rhinitis (mean age, 8.5 +/- 1.4 years). On 3 different days the children received terfenadine, 60 mg, chlorpheniramine, 4 mg, or placebo; the tests were performed before and 2 to 2 1/2 hours after dosing. Both terfenadine and chlorpheniramine suppressed the histamine-induced wheal and flare compared with baseline and with placebo; terfenadine was significantly more effective (p < 0.05). Terfenadine did not increase the latency of P300-event-related potentials at the parietal (Pz) or frontal (Fz) scalp electrodes compared with baseline, in contrast to chlorpheniramine and placebo, which did increase P300 latency. Terfenadine and placebo did not increase somnolence compared with baseline, but chlorpheniramine did. In children, as previously documented in adults, terfenadine has a more favorable benefit/risk ratio than chlorpheniramine, as shown by production of significantly greater peripheral histamine blockade and significantly less central nervous system dysfunction.

Pharmacokinetics and pharmacodynamics of ebastine in children

Ebastine is a new piperidine-containing, relatively nonsedating second-generation H1-receptor antagonist. In a double-blind, parallel-group study of a single 5 mg or 10 mg dose of ebastine syrup used to treat allergic rhinitis in 20 children aged 6 to 12 years, we tested the hypothesis that the medication would have a duration of action of at least 24 hours. We measured plasma concentrations of carebastine, the pharmacologically active metabolite of ebastine, and the wheals and flares produced by epicutaneous tests with histamine phosphate, 1.0 mg/ml. Ebastine was absorbed well; peak carebastine concentrations occurred approximately 3 hours after dosing. Mean plasma elimination half-life values of carebastine ranged from 10 to 14 hours. The pharmacokinetics of carebastine were linear and dose independent in the dosage range studied. After the 5 or 10 mg dose, there were no significant differences between mean plasma elimination half-life values, mean oral clearance values, or mean apparent volumes of distribution. Mean peak plasma carebastine concentrations and mean areas under the plasma carebastine concentration-time curve after the 10 mg dose were 1.93 and 1.76 times, respectively, the values obtained after the 5 mg dose. Both doses significantly reduced the histamine-induced wheal-and-flare areas for up to 28 hours compared with predose values. The differences in effect between the doses generally were not statistically or clinically significant. No adverse effects were noted. We conclude that ebastine, an effective H1-receptor antagonist with a prompt onset of action and a long duration of action, is suitable for once-daily administration to children.