A protocol for assessing the duration of blood pressure control by once-daily medication and improving control by modifying timing of dosage and choice of drug type for longer half life: an illustrative case report.
John Jackson FFOM, Managing Consultant, Jackson Hocking Limited, ,
29, Station Road, Blackwell, Bromsgrove, GB-B60- 1QB
Issues in the frequency of doses in the treatment of hypertension have been both the need to maintain 24-hour control and the need for a regime that ensures high compliance with the dosing schedule. This paper describes how the author (who has been treated for hypertension for 50 years) managed his suspicion, based on symptoms such as a pounding heart beat, that his regime was not achieving 24 hour control. This includes a simple protocol, an example of adjustment of medication and dosing that improved the duration of control and a discussion of the practicality of the adoption of the protocol.
The medication prior to the adjustment was quinapril 40mg, bisoprolol fumarate 10mg and doxazosin mesylate 4mg, each once a day in the morning. Blood pressure was measured in the right arm with a wide cuff in the seated position using an Omron M5-I instrument. The elbow was flexed and the whole of the elbow, forearm and hand were resting on a table of suitable height. In a preliminary trial it was determined that measurements with the instrument decreased for the first three consecutive readings and were more or less constant thereafter and that the reduction in blood pressure resulting from the morning dosing were achieved 2 ½ hours after dosing.
Phase 1 of the protocol involved measuring the blood pressure three times consecutively on rising and then taking the morning medication. Approximately 2 ½ hours later, the blood pressure was taken again three times consecutively. This was repeated for four consecutive days. The results were recorded in an Excel spreadsheet as in Table 1.
Table 1
The mean difference between the lowest pre-dose and the lowest post dose readings was 29/21 mm.Hg. and the heart rate decreased by an average of 6.8 beats per minute.
After ascertaining half lives of the medication and discussion with the GP, quinapril was changed to lisinopril and the bisoprolol was changed from 10mg in the morning to 5 mg bd. A week after the change, the protocol was repeated (Phase 2) and the results and derivatives of both sets of data are presented in Table 2.
Table 2
As a result of the change in medication and dosing, the mean difference between the lowest pre-dose and the lowest post dose readings was 2/2.8 mm.Hg. but the heart rate increased by an average of 3 beats per minute, a reduction of 27/18 mm.Hg compared with the previous regime. The blood pressure on rising had decreased by 21/13 mm.Hg but the blood pressures post-morning medication was 6/5 higher and the heart rate was 4bpm higher. This possibly reflects the fact that the morning dose of bisoprolol had been halved. While it might be possible to consider increasing the morning dose of bisoprolol to 10mg in the morning and 5mg at night, an average resting blood pressure in the region of 147/84 and 146/81 is probably satisfactory in a male aged 70.
Electronic sphygmomanometers are not expensive and, in general, are accurate enough for the purpose of making comparisons over a relatively short period. While there is an instrument available at £15.99, this has only one memory and it is useful to have more memories so that the three measurements can be made without interruption to write down the results. The Omron M10 IT instrument is available at £34.95. Many patients either own or would be prepared to purchase an instrument in order to monitor their blood pressure and most practices could purchase an instrument to lend to patients for an affordable deposit.
The use of the instruments can be taught easily and a simple table can be produced on which the results can be recorded. Many patients are comfortable using Excel and the spreadsheet could be attached to an email and sent to a patient by the practice and the completed table could be emailed back for incorporation in the computerised medical records. The protocol may be more acceptable than ambulatory blood pressure monitoring, though it does not provide as much information.
If the difference in phase 1 is small (and the blood pressure is satisfactory, there is no need to proceed to phase 2. If, after modification of the treatment regime, the difference between the BP on rising and the BP after morning treatment is still excessive, the data from phase 2 can be considered to be the data for a new phase 1 and a new phase 2 can be recorded after a further adjustment of therapy.