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RESEARCH REPORT |
1 Department of Hospital Dentistry and
4 Hospital Pharmacy, Malmö University Hospital, SE-205 02 Malmö, Sweden;
2 Department of Oral Diagnostics and
3 Department of Cariology, Faculty of Odontology, Malmö University, SE-205 06 Malmö, Sweden; and
5 Department of Pharmacology, Göteborg University, Box 431, SE-405 30 Göteborg, Sweden;
* corresponding author, bengt.gotrick{at}skane.se
| ABSTRACT |
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KEY WORDS: pilocarpine oral dryness randomized controlled trial drug-induced xerostomia
| INTRODUCTION |
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Pilocarpine hydrochloride is a parasympathomimetic agent that binds unselectively to muscarinic receptors and exerts a broad spectrum of pharmacological effects, including stimulation of salivary, sweat, and lachrymal glands (Brown and Taylor, 2001). Several double-blind, placebo-controlled trials have demonstrated significant increases in salivary secretion during the administration of oral pilocarpine to patients with radiation-induced xerostomia (Greenspan and Daniels, 1987; Johnson et al., 1993; LeVeque et al., 1993; Rieke et al., 1995; Jacobs and van der Pas, 1996) and to patients with xerostomia due to Sjögrens syndrome (Fox et al., 1991; Vivino et al., 1999). Pilocarpine (Salagen®) tablets are currently used both for the treatment of radiation-induced dry mouth and in patients with Sjögrens syndrome dry mouth or dry eyes. In a recent study, pilocarpine was shown to cause relief of xerostomia in morphine-treated cancer patients within 24 hrs, but no quantitative estimation was performed (Mercadante et al., 2000). We undertook the present study to establish whether the oral administration of pilocarpine re-establishes salivary secretion during drug-induced oral dryness. It involved a double-blind, placebo-controlled, parallel-group study to determine the efficacy of pilocarpine treatment in healthy volunteers pre-treated with tramadol. Tramadol has low affinity for opioid receptors but also exerts its effect by direct modulation of central mono-aminergic pathways and has adverse effects similar to those of other opioids, including oral dryness (Lee et al., 1993; Lewis and Han, 1997). Since tramadol has been reported to reduce salivary secretion in less than 10% of treated patients (Lee et al., 1993), and the present study aimed at examining pilocarpine treatment of drug-induced hyposalivation, a reduction of the flow of saliva of less than 40% was taken as an exclusion criterion.
| MATERIALS & METHODS |
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Study Design and Assessment
The amount of unstimulated saliva secreted at rest was measured according to a standard method (Gutman and Ben-Aryeh, 1974; Osterberg et al., 1984) that involved the collection of samples for 5 min at 15-minute intervals over 2 hrs. Subjects were not allowed to eat or drink during this two-hour period, or for the preceding hour. During collection periods, the subjects were seated and relaxed and leaned slightly forward so that saliva accumulated sublingually in the mouth. It was then allowed to drop passively into a small plastic beaker, held directly beneath the lower lip. After determination of the basal secretory rate (baseline, day 1) and the subsequent administration of tramadol (50 mg 3x/day over days 2 and 3), the subjects were randomly assigned to one of three groups: one given no further treatment (Control group), one given pilocarpine (5 mg tablet by oral intake; Pilocarpine group), and the other given a placebo (Placebo group; Fig. 1
). Random assignment was computer-generated, with a block size of six, and beakers, which were number-connected to the coding, either empty or containing a capsule, were given to the participants consecutively. Tramadol was administered orally at 7 a.m., 1:30 p.m., and 9 p.m. on day 2 and at 7 a.m. and 1:30 p.m. on day 3, since we hoped to achieve a steady-state concentration of the drug by the afternoon on day 3. We measured the quantity of secreted unstimulated saliva for 3 consecutive five-minute periods to determine the effect of tramadol. The Pilocarpine and Placebo group participants were then given a capsule containing either pilocarpine or placebo (double-blind) together with enough water for swallowing (the Control group was supplied with the same volume of water). After 15 min, saliva was collected by the same procedure for saliva collection as on day 1. After the test, a subjective assessment of efficacy and adverse effects was made by questionnaire on day 3, before and after pilocarpine or placebo treatment. Questions were presented as three-point categorical questions (increase in, no change, or decrease in salivary secretion; and no, moderate, or severe adverse effect).
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Calculations
A pilot study was performed including six subjects for power analysis of a three-group study design. We needed to recruit 45 participants to achieve a 90% power to detect an increase in unstimulated whole saliva from a dry mouth level (0.15 mL per min) to the level of average secretion for healthy individuals (0.35 mL per min), with a two-sided test and a type I error of 5%. We allowed for screening failures and dropout during the study by increasing the number of subjects needed in each treatment group from 15 to 20. Assessment was based on per protocol analysis and statistical significance determined by one-way analysis of variance (ANOVA) followed by the Bonferroni multiple-comparison test. P values of 0.05 or less were regarded as statistically significant. Values are presented as means ± SEM.
Ethics Considerations
All patients consented verbally and in writing to participate in the study. The Ethics Committee of the University of Lund approved the study as well as the research protocol. The trial was carried out according to the Helsinki Declaration.
| RESULTS |
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Effect of Tramadol Treatment
Tramadol treatment significantly decreased salivary flow rates, roughly halving the rate of secretion (p < 0.01, n = 60). Eighteen subjects felt no discomfort during tramadol treatment; 22 considered it to be acceptable, while 20 found it to be unpleasant. When reported, discomfort was attributable to the well-known adverse effects of tramadol, most frequently somnolence and dizziness. However, the opioid did not have any effect on pilocarpine-induced salivation. In the pilot study, the peak responses to pilocarpine were 1.36 ± 0.35 mL/min and 1.36 ± 0.24 mL/min, before and after tramadol administration, respectively.
Effect of Pilocarpine
Pilocarpine invariably increased the flow of saliva significantly 30 min after intake (Fig 1
; p < 0.050.001). The time period until maximal flow rate was reached varied for the individuals, but generally occurred within 3090 min. Considering each individuals maximum, the means of these responses were slightly greater than the maximum of the time-response curve (0.94 ± 0.17 vs. 0.66 ± 0.19 mL/min; Table
and Fig. 1
, respectively). The flow subsequently declined slowly during the rest of the 120-minute observation period, but without ever returning to the tramadol level (dryness). In two individuals, however, the flow rate increased steadily over the whole of the observation period. Salivary flow rates following administration of placebo (0.15 ± 0.02 mL/min) remained similar to the tramadol level (0.15 ± 0.02 mL/min) throughout the study, and the responses in the placebo group were similar to the flow rate in the control group (Fig. 1
). Mean maximal salivary flow rate after pilocarpine treatment was four-fold greater than after placebo and four-fold greater than flow rate after tramadol treatment (dryness). Pilocarpine also increased the flow of saliva above the rate recorded before the administration of tramadol (i.e., baseline; Table
). None of the participants given pilocarpine found it unpleasant, although two reported sweating.
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| DISCUSSION |
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Salivary glands are activated by sympathetic and parasympathetic efferents originating in primary salivary centers (Strack et al., 1989; Jansen et al., 1992). It is reasonable to expect that xerogenic drugs exert their effects by either of the following mechanisms: (1) blockade of muscarinic or adrenergic receptors in the salivary glands; or (2) inhibition of activity in the primary salivary centers, resulting in a decreased outflow of efferent impulses to the salivary glands. Since activation of muscarinic receptors is by far the most potent natural stimulus for salivation, the parasympathomimetic pilocarpine is well-suited for treatment of oral dryness caused by xerogenic drugs that do not involve muscarinic receptor blockade. Tramadol is apparently such a drug, since it did not affect pilocarpine-induced fluid secretion. Pilocarpine has been the drug of choice for treatment of radiation-induced xerostomia, dry mouth, and dry eyes in patients with Sjögrens syndrome (Johnson et al., 1993; Vivino et al., 1999). Currently, pilocarpine, but not placebo treatment, effectively and rapidly reversed tramadol-induced oral dryness. The results eliminate any possible placebo effect and indicate that even though drug treatment may vastly hamper secretion, the secretory capacity still remains, and secretion can be re-established with a short latency. The results confirm the assumption made by Mercadante et al.(2000), that a placebo-effect could be neglected.
In the current study, correlation between reductions in salivary flow and the subjects reported experience was very weak or absent, whereas there was some correlation between these parameters after pilocarpine. A 50% reduction in salivary flow has been postulated as a limit for patients experiencing xerostomia, although it is not known to what level secretory output must become diminished before oral dysfunction will become clinically significant (Ship et al., 1991). In the present study, some subjects did not experience any change in sensation, even if the flow was reduced by more than 50%, and similarly, some reported a sensation of decrement even though there was a modest increase in flow. Analysis of the data indicates that subjective estimation of a change in flow is of very limited value in the evaluation of xerogenic drugs. This is further underlined by the fact that tramadol induced hyposalivation in 80% of the participants in the present study, which is in marked contrast to what has been reported in the literature (reductions in only 10% of patients; Lee et al., 1993). This difference may be explained by quantification of the flow of saliva in contrast to evaluation by asking subjects about their experienced flow rate. Pilocarpine caused no adverse effects, except that two (out of 17) individuals complained of increased sweating. In previous treatments with pilocarpine, patients have complained of severe nocturnal sweating and therefore discontinued the medication (Wiseman and Faulds, 1995). However, since a beneficial effect was obtained in the present study with a single dose, and after a short latency, it seems likely that schedules for its administration could be devised which would avoid such undesirable effects.
The current study thus shows that oral pilocarpine can re-establish the flow of saliva in pharmacological states of oral dryness, and that low-dose regimes may be sufficient to restore secretion. The effect of pilocarpine treatment on quality of life, the prevention of dental caries, or the composition of the saliva secreted is presently unknown.
| ACKNOWLEDGMENTS |
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Received February 28, 2003; Last revision December 29, 2003; Accepted March 5, 2004
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