Measuring treatment compliance of men with non-gonococcal urethritis receiving oxytetracycline combined with low dose phenobarbitone

Effect of patient education on adherence to drug treatment for rheumatoid arthritis: a randomised controlled trial

OBJECTIVE

To determine whether a patient education programme (PE) would improve rates of adherence to a slow acting antirheumatic drug and to assess any subsequent effect on patient outcome.

METHODS

A randomly controlled study comprising 100 patients with rheumatoid arthritis (49 control CG; 51 experimental EG) requiring D-penicillamine (DPA). The same practitioner saw patients on seven occasions, for the same length of time. The EG received 7 x 30 minute one to one sessions of PE, while the CG received standard management. The primary measure of adherence was a pharmacological marker (phenobarbitone) encapsulated with the DPA assayed at monthly intervals for six months. Plasma viscosity (PV), C reactive protein, articular index, morning stiffness, and pain score were used to assess outcome.

RESULTS

454 blood samples were collected and assayed and the pharmacological marker showed the EG to be significantly more adherent on more occasions than the CG (p<0.05). Patterns of adherence over time showed that at 12 weeks 86% (38/44) of those in the EG compared with 64% (29/45) of the CG remained adherent (p=0.01). These trends continued and by the end of the study 85% (29/34) of the EG compared with 55% (23/42) of the CG were taking their DPA as prescribed. Fifteen patients (12 from the EG) experienced side effects requiring study withdrawal and 14 patients requested study withdrawal (two from the EG). On study entry patients in the CG had significantly higher levels of PV than the EG and this remained so throughout the research. However, on completion, the health status of patients in both groups had improved significantly (p<0.01).

CONCLUSIONS

PE significantly increased adherence to DPA and its effects persisted over a period of six months. No additional clinical benefit was detected in the EG in comparison with the CG.

Compliance with oral corticosteroids during steroid trials in chronic airways obstruction

BACKGROUND

Corticosteroid trials are an important part of the assessment of patients with chronic airways obstruction, but false negative results will occur if the treatment is not taken. To determine compliance low dose phenobarbitone has been used as a marker.

METHODS

Thirty six patients referred to a chest clinic for assessment of their airways obstruction were studied. They were instructed to take eight capsules (each containing 5 mg prednisolone and 0.5 mg phenobarbitone) per day for two weeks. The response was assessed by home peak flow monitoring and clinic spirometric tests. Plasma phenobarbitone levels were measured after the trial to enable calculation of the dose to plasma concentration ratio (level to dose ratio, LDR) and the result was compared with the reference range for fully compliant individuals.

RESULTS

Five patients defaulted from follow up, 23 had LDR values within the expected range, and eight had low LDR values consistent with poor compliance. The nine patients with steroid responsive disease (> 20% improvement in peak flow or spirometric parameters) all had LDR values in the expected range.

CONCLUSION

Excluding those who defaulted whose compliance must be questionable, eight (26%) patients did not fully comply with the steroid trial. Not all patients who fail to respond to a two week home steroid trial have a steroid "unresponsive" disease.

The prediction of steady-state plasma phenobarbitone concentrations (following low-dose phenobarbitone) to refine its use as an indicator of compliance

1. A model for predicting the steady-state plasma concentration of phenobarbitone following low-dose phenobarbitone used as an indicator of compliance was derived using data for 10 healthy volunteers. 2. Each volunteer was given a single 30 mg oral dose of phenobarbitone and the pharmacokinetics were described. Subsequently, volunteers were given phenobarbitone 2 mg daily for 28 days and a further pharmacokinetic profile determined during and after this period. 3. An initial predicted estimate of steady-state plasma drug concentration was made using each volunteer's demographic details. This estimate was revised by Bayesian analysis using single timed samples (24, 48, 72 or 96 h) following the single dose. 4. The model was tested on a further 10 healthy volunteers given a single 8 mg dose and who were subsequently given 2 mg daily for 28 days. 5. The revised estimate of peak steady-state plasma phenobarbitone concentration utilising the 96 h post-single dose concentration (356 ng ml-1) was least biased (mean prediction error +/- 95% CI = 10.6 +/- 19.8 ng ml-1) and most precise (root mean square error +/- 95% CI = 28.3 +/- 19.0 ng ml-1). In all cases the peak or trough steady-state drug concentration was within 13% of the predicted value. 6. The model reflected compliance accurately in a further eight volunteers with simulated partial (two-thirds) compliance. 7. The use of a predictive model using Bayesian analysis to estimate expected steady-state plasma phenobarbitone concentrations could increase further the usefulness of low-dose phenobarbitone as an indicator of compliance.