A pharmacokinetic–pharmacodynamic model for intrathecal baclofen in patients with severe spasticity

Aims

Intrathecal baclofen (ITB) has proven to be an effective and safe treatment for severe spasticity. However, although ITB is used extensively, clinical decisions are based on very scarce pharmacokinetic–pharmacodynamic (PKPD) data. The aim of this study was to measure baclofen CSF concentrations and clinical effects after administration of various ITB boluses in patients with spasticity and to create a PKPD model for ITB.

Methods

Twelve patients with severe spasticity received four different bolus doses of ITB (0, 25, 50, 75 μg and an optional dose of 100 μg), administered via a catheter with the tip at thoracic level (Th) 10. After each bolus, 10 CSF samples were taken at fixed time intervals, using a catheter with the tip located at Th12. Clinical effect was assessed by measuring spasticity with the Modified Ashworth Scale (MAS). These data were used to develop a PKPD model.

Results

All patients achieved an adequate spasmolytic effect with ITB doses varying from 50 to 100 μg. No serious side effects were observed. CSF baclofen concentrations, as well as the clinical effects, correlated significantly with ITB doses. The PK model predicted a steep spinal concentration gradient of ITB along the spinal axis. The clinical effect could be predicted using a delayed‐effect model.

Conclusions

ITB is an effective and safe therapy with, however, a steep concentration gradient along the spinal axis. This means that the administered baclofen is staying mainly around the catheter tip, which stresses the importance to position the ITB catheter tip closely to the targeted spinal level.     

A general practice study to compare the efficacy and tolerability of a spray (‘Otomize’) versus a standard drop formulation(‘Sofradex’) in the treatment of patients with Otitis externa

Summary

In an open, multi-centre study in general practice, a comparison was made of the efficacy, tolerability and acceptability of a neomycin/ dexamethasone preparation administered by metered-dose spray (‘Otomize’) and a framycetin/gramicidin/ dexamethasone preparation (‘Sofradex’) administered as drops in 60patients with otitis externa. Patients were allocated at random to receive one or other preparations 3-times daily for 10 days and were followed-up again 14 days after cessation of therapy. Clinical assessments were carried out under observer blind conditions on entry (Day 0) and on Days 10 and 24 of the severity of erythema, swelling and debris in the affected ear(s). A global assessment of clinical outcome was made by the doctor on Day 10. There were no significant differences in the two groups at the start of treatment. Significant improvement occurred in both groups from Day 0 to Day 10 and from Day 10 to Day 24 in all symptoms, with the proportion symptom-free in the ‘Otomize’ group significantly greater than in the ‘Sofradex’ group at 24 days, and approaching significance at 10 days. Significantly more patients in the ‘Otomize’ group were rated as having a good clinical outcome by the physician, and fewer patients experienced discomfort on application. Few side-effects were reported by either treatment group, none necessitating discontinuation of therapy.