Paediatric pharmacokinetics: key considerations

A number of anatomical and physiological factors determine the pharmacokinetic profile of a drug. Differences in physiology in paediatric populations compared with adults can influence the concentration of drug within the plasma or tissue. Healthcare professionals need to be aware of anatomical and physiological changes that affect pharmacokinetic profiles of drugs to understand consequences of dose adjustments in infants and children. Pharmacokinetic clinical trials in children are complicated owing to the limitations on blood sample volumes and perception of pain in children resulting from blood sampling. There are alternative sampling techniques that can minimize the invasive nature of such trials. Population based models can also limit the sampling required from each individual by increasing the overall sample size to generate robust pharmacokinetic data. This review details key considerations in the design and development of paediatric pharmacokinetic clinical trials.

Adverse drug reaction teaching in UK undergraduate medical and pharmacy programmes

OBJECTIVES

To assess the extent of teaching about the Committee on Safety of Medicine's Yellow Card scheme and adverse drug reactions within UK Schools of Medicine and Pharmacy.

METHODS

A self-completed questionnaire sent to all heads of undergraduate schools of medicine and pharmacy within the UK.

RESULTS

The majority of undergraduate syllabi feature the Yellow Card Scheme. Knowledge of the Yellow Card Scheme was assessed in 79% of pharmacy programmes and 57% of medical schools. Specialist speakers on the Yellow Card Scheme were infrequently used. Fewer than half of respondents provided students with a guide to reporting ADRs (43% pharmacy and 43% medical). There is some disagreement about the value of supplying students with printed material about the Yellow Card Scheme. Half of medical Schools did not think that supplying 'Current Problems In Pharmacovigilance' would be useful.

CONCLUSIONS

It was found that in both medicine and pharmacy, courses differed substantially in teaching about the Yellow Card Scheme and adverse drug reactions (ADRs). There is scope for increased involvement of the Medicines and Healthcare products Regulatory Agency in undergraduate education, in line with recommendations from the National Audit Office.

A comparison of the effects of the calcium entry blockers, verapamil, diltiazem and flunarizine against contractions of the rat isolated aorta and portal vein

1. The actions of the chemically distinct calcium entry blockers, verapamil (Ver), diltiazem (Dlz) and flunarizine (Flu) have been compared in rat isolated aorta and portal vein. 2. KCl-induced contractions of the rat aorta depend exclusively upon extracellular Ca2+, whereas, those induced by noradrenaline (NA) rely upon Ca2+ from intra- and extracellular sources. The NA-induced contraction was pharmacologically dissected under Ca2+-free conditions revealing a contraction dependent upon intracellular Ca2+ (EGTA-resistant response) or a low concentration of prazosin which left a contraction which was mediated by extracellular Ca2+ (prazosin-resistant response). 3. The portal vein produced spontaneous rhythmic contractions and a sustained contraction to NA and KCl; however, all responses appeared to depend exclusively upon extracellular Ca2+. 4. In the aorta, contractions which might be expected to depend upon Ca2+-entry through voltage-operated channels (KCl-induced contraction) showed similar sensitivities to Ver, Dlz and Flu whereas, marked differences in the sensitivity to these agents was noted against contractions which appear to depend upon Ca2+-entry through receptor-operated channels (prazosin-resistant response). Only Dlz reduced contractions mediated by intracellular Ca2+ (EGTA-resistant response). 5. In the portal vein, Ver and Dlz caused similar pronounced reductions of spontaneous and NA of KCl-induced contractions. In contrast, these contractions of the portal vein were unaffected by Flu except at a concentration of 10 microM. However, contractions induced by addition of Ca2+ (0-14 mM) to previously depolarized portal veins could be reduced by Flu (100 nM-10 microM). 6. The present study indicates that in the rat aorta, contractions mediated by intracellular Ca2+ and depolarization or receptor-activated Ca2+ entry can be pharmacologically dissected and that these processes show different sensitivities to calcium entry blockade. Of the agents tested, Ver displays the properties most commonly associated with an ideal calcium entry blocker. Ca2+-activation mechanisms in the portal vein differ from those in the aorta resulting in a different spectrum of selectivity of the calcium entry blockers studied.

Differential effects of hypoxia upon contractions evoked by potassium and noradrenaline in rabbit arteries in vitro

1. A study has been made on isolated sections of rabbit femoral, renal and saphenous arteries of the effects of graded hypoxia (reducing bath PO2 from 110 mmHg, normoxia, to 55, 23 and 6 mmHg) upon contractile responses evoked by noradrenaline (NA) and KCl to 80% of maximum. 2. Potassium-evoked contractions were not affected by moderate hypoxia but were reduced in all vessels to 70-80% of the control response in normoxia, by exposure to either PO2 23 or 6 mmHg. Potassium-evoked contractions were virtually abolished by Ca2(+)-free Krebs solution and greatly reduced by verapamil (10 microM), indicating that they relied upon influx of extracellular Ca2+. 3. By contrast, NA-evoked contractions were reduced in a graded fashion in all vessels by exposure to graded levels of hypoxia and at PO2 6 mmHg they were significantly more reduced than K(+)-evoked contractions. Noradrenaline-evoked contractions of femoral arteries were most affected, being reduced to 80% of control at PO2 55 mmHg, and to 28% and 6% of control at PO2 23 and 6 mmHg respectively. Contractions in renal arteries were least affected, being reduced to only 47% of control at PO2 6 mmHg. 4. Noradrenaline-evoked contractions were reduced, but not abolished, in Ca2(+)-free Krebs solution. In normoxia, they reached 42%, 35% and 25% of control responses in the presence of Ca2+ in femoral, renal and saphenous arteries respectively. The Ca2(+)-free responses of the femoral and saphenous arteries were significantly different, indicating that the femoral arteries were least dependent and saphenous most dependent on influx of extracellular Ca2+ for contraction. 5. Contractions evoked by NA in Ca2(+)-free Krebs solution were not significantly affected by PO2 55 mmHg. Those evoked in saphenous arteries were not affected by more severe hypoxia, but in renal arteries they were significantly reduced at PO2 23 mmHg, while in femoral arteries they were significantly reduced both at PO2 23 and at PO2 6 mmHg. 6. Verapamil produced changes similar to Ca2+ withdrawal. Contractions evoked by NA in the presence of verapamil were affected by hypoxia in a similar way to those evoked in the absence of Ca2+. 7. These results indicate that the inhibition of contraction induced by hypoxia is not simply dependent upon inhibition of Ca2+ influx. Instead, we propose that receptor-operated rather than voltage-operated processes are particularly vulnerable, there being inhibition of the components of contraction which are dependent on receptor-operated Ca2+ influx and release of intracellular Ca2+.

Documentation of antibiotic prescribing controls in UK NHS hospitals

OBJECTIVES

To identify the types, prevalence and nature of antibiotic prescribing control documents within NHS hospitals in the UK.

METHODS

A self-completion postal questionnaire was sent to each Chief Pharmacist at 465 NHS hospitals in 2001/2002. This contained questions covering hospital demographics, and hospital antibiotic prescribing control documentation, including format, dissemination, approval and review processes.

RESULTS

In total, 253 (54%) completed questionnaires were returned. Of these, 168 respondents' hospitals had an antibiotic formulary, 107 had a policy for antibiotic prescribing and 216 had guidelines on antibiotic use. All three types of antibiotic prescribing documents were used by 82 hospitals but 18 did not have any documents; 44% of formularies, 45% of policies and 35% of guidelines were available electronically. The Drug and Therapeutics Committee was the most frequently cited body for document approval and approximately one-third of documents had been approved during the current year of the questionnaire. Only about one-half of responding hospitals had an annual review of documents.

CONCLUSIONS

Despite publication of high-profile national guidance in response to growing concerns regarding antimicrobial resistance, there has been little increase in the use of antibiotic prescribing control documents in NHS hospitals over the past decade. It is clear that appropriate controls for antibiotic prescribing are not yet universally applied in the UK and recommendations for action have been proposed.

Effects of hypoxia upon contractions evoked in isolated rabbit pulmonary artery by potassium and noradrenaline

1. Comparisons have been made between rabbit thoracic aorta and main pulmonary artery of the effects of hypoxia upon contractions evoked by noradrenaline (NA) and KCl (K+). 2. Contractions were evoked in cylindrical sections of pulmonary artery and aorta, mounted for isometric recording of tension, by NA and K+ (at ED80) in normoxia (PO2 110 mmHg) and hypoxia (PO2 23 or 7 mmHg). Contractions were also evoked in Ca2(+)-free conditions with EGTA to prevent influx of extracellular Ca2+. All contractions are expressed as a percentage of normoxic response in the presence of Ca2+. 3. Potassium-evoked contractions of aorta and pulmonary artery were reduced to a similar extent by both levels of hypoxia, to 85 and 92% respectively. As expected K(+)-evoked contractions were virtually abolished by Ca2(+)-free conditions. It is proposed that hypoxia has a small inhibitory effect upon contraction mediated by Ca2+ influx via voltage-operated Ca2+ channels. 4. In the aorta in the presence of Ca2+, hypoxia reduced NA-evoked contractions to 84% at PO2 23 mmHg and 34% at PO2 7 mmHg. In the absence of Ca2+, NA-evoked contractions reached 73% in normoxia, but only 43 and 21% at PO2 23 and 7 mmHg respectively. These results suggest that hypoxia reduces the component of contraction that is mediated by release of intracellular Ca2+ and possibly that mediated by agonist-induced Ca2+ influx. 5. In the pulmonary artery also, NA-evoked responses in the absence of Ca2+ were reduced from 60% in normoxia, to 49 and 38% at PO2 23 and 7 mmHg. But, in the presence of Ca2+, hypoxia potentiated NA-evoked contractions to 113 and 111% at PO2 23 and 7 mmHg respectively. It is proposed that in the pulmonary artery, hypoxia reduces the component of contraction mediated by release of intracellular Ca2+, but facilitates that mediated by extracellular Ca2+. Possible mechanisms are discussed.

Concordance in Muslim patients in primary care

Focal points

The impact of a computerised decision support system on antibiotic usage in an English hospital

Background Antimicrobial resistance is correlated with the inappropriate use of antibiotics. Computerised decision support systems may help practitioners to make evidence-based decisions when prescribing antibiotics. Objective This study aimed to evaluate the impact of computerized decision support systems on the volume of antibiotics used. Setting A very large 1200-bed teaching hospital in Birmingham, England. Main outcome measure The primary outcome measure was the defined daily doses/1000 occupied bed-days. Method A retrospective longitudinal study was conducted to examine the impact of computerised decision support systems on the volume of antibiotic use. The study compared two periods: one with computerised decision support systems, which lasted for 2 years versus one without which lasted for 2 years after the withdrawal of computerised decision support systems. Antibiotic use data from June 2012 to June 2016 were analysed (comprising 2 years with computerised decision support systems immediately followed by 2 years where computerised decision support systems had been withdrawn). Regression analysis was applied to assess the change in antibiotic consumption through the period of the study. Result From June 2012 to June 2016, total antibiotic usage increased by 13.1% from 1436 to 1625 defined daily doses/1000 bed-days: this trend of increased antibiotic prescribing was more pronounced following the withdrawal of structured prescribing (computerised decision support systems). There was a difference of means of - 110.14 defined daily doses/1000 bed days of the total usage of antibiotics in the period with and without structured prescribing, and this was statistically significant (p = 0.026). From June 2012 to June 2016, the dominant antibiotic class used was penicillins. The trends for the total consumption of all antibiotics demonstrated an increase of use for all antibiotic classes except for tetracyclines, quinolones, and anti-mycobacterial drugs, whereas aminoglycoside usage remained stable. Conclusion The implementation of computerised decision support systems appears to influence the use of antibiotics by reducing their consumption. Further research is required to determine the specific features of computerised decision support systems, which influence increased higher adoption and uptake of this technology.

The effects of verapamil upon noradrenaline-induced contraction of the rat isolated aorta following acute and prolonged alterations in PO2

1. Noradrenaline (NA;ED90) caused a contraction of the rat aorta which could be separated into two components, a rapid response mediated by release of intracellular Ca2+ and a more slowly developing contraction which relied principally upon Ca2+ influx. 2. Exposure to acute (30 min) hypoxia has been previously shown to reduce the NA-induced contraction (by 28.0 +/- 2.7%, n = 168) which recovered completely upon re-oxygenation (recovery response). In the present study, prolonged exposure to hypoxia (70 h) caused a more pronounced reduction (39.7 +/- 3.0%, n = 90) of the NA-induced contraction, but, re-oxygenation then produced incomplete recovery to 77.9 +/- 3.9% (n = 90) of the control response. 3. Prolonged exposure to 95% O2 caused a 36.5 +/- 3.1% (n = 42) reduction of NA-induced contractions, whereas prolonged exposure to 21% O2 only caused a small (12.6 +/- 3.4%, n = 6) depression of these responses. 4. The component of the NA-induced contraction mediated by release of intracellular Ca2+ is 39.8 +/- 1.3% (n = 83) of the NA contraction in Ca-containing Krebs solution and was previously found to be unaffected by acute hypoxia. However, following prolonged exposure to either hypoxia or 21% O2, this component only reached 30.7 +/- 2.2% (n = 32) or 28.3 +/- 0.9% (n = 6) of the control response, respectively. Prolonged exposure to 95% O2 caused a more pronounced reduction of this component of contraction which then reached 19.1 +/- 2.1% (n = 12) of the control response. 5. Verapamil (10nM-10 microM) produced similar concentration-dependent reductions of NA-induced contractions elicited during control conditions or acute hypoxia; under these conditions, 1 microM verapamil caused a 34.1 + 6.9% (n = 6) and a 41.8 + 2.9% (n = 18) reduction of these responses respectively. However, recovery responses caused by re-oxygenation of tissues exposed to acute hypoxia were more sensitive to verapamil which, at a concentration of 1 microM, caused a 59.2 + 2.7% (n = 18) reduction of these responses. Verapamil (10 nM-10 microM) also caused similar pronounced concentration-dependent reductions of contractions elicited during prolonged exposure to normoxia or hyperoxia and of recovery responses obtained following re-oxygenation of tissues exposed to prolonged hypoxia; 1 microM verapamil caused a 62.5 + 1.1% (n = 6), 77.2 + 3.8% (n = 12) and a 68.0 + 4.3% (n = 12) reduction of these responses respectively. In contrast, contractions elicited during prolonged hypoxia were less sensitive to verapamil which at a concentration of 1 microM only caused a 16.2 + 2.2% (n 12) reduction of these responses. 6. The present study indicates that prolonged exposure of the rat aorta to either hypoxic or oxygenated conditions causes attenuation of NA-induced contraction. However, these effects are also accompanied by changes in tissue Ca2+ handling which differ under each condition and might account for the observed modifications in tissue sensitivity to the calcium-entry blocker verapamil.

Professionals' awareness of operational antibiotic prescribing controls in UK NHS hospitals

In recent years, there have been increasing recommendations for multidisciplinary collaboration between clinical pharmacists and medical microbiologists in an attempt to control the quality (and quantity) of antibiotic prescribing. A questionnaire addressing the utilization of antibiotic prescribing controls was sent to the chief pharmacist and medical microbiologist in UK NHS hospitals. Responses were received from both the chief pharmacist and the medical microbiologist employed in the same hospital from 83 hospitals (a 30% response rate from two independent studies). A high level of disagreement and poor awareness was identified between the interprofessional staff groups regarding the existence of antibiotic formulary (with disagreement between the two groups, or not known by one or both respondents, in 46% of the paired hospitals, N = 38) and guideline documents (13%, N = 11), performance of antibiotic prescribing audits (40%, N = 33), and whether pharmacists (52%, N = 43) and medical microbiologists (77%, N = 64) monitored physician compliance with antibiotic prescribing control documents. This study has identified poor knowledge of the existence of basic antibiotic prescribing control mechanisms and the role of professional colleagues. It is suggested that there is some way to go before 'Agenda for Change' principles of flexible and collaborative roles are met.

An investigation of the actions of diltiazem on rat aorta exposed to acute hypoxia followed by re-oxygenation

1 The effects of diltiazem and removal of extracellular Ca2+ were examined on contractions, of the rat isolated aorta, to noradrenaline (NA) and high K+, during exposure to oxygenated conditions and hypoxia followed by re-oxygenation. 2 Exposure to hypoxia caused a similar reduction of contractile responses to NA and KCl, while re-oxygenation restored contractile activity. 3 Ca2+-free conditions abolished responses to KCl but a transient response to NA remained which was resistant to hypoxia. 4 Diltiazem produced similar reductions of responses to NA during both oxygenated conditions and hypoxia, whereas during re-oxygenation the effects of diltiazem upon responses to NA were enhanced. 5 Diltiazem produced a more pronounced reduction of responses to KCl than of responses to NA. However, the reduction of responses to KCl by diltiazem was not modified by the changes in PO2 examined in the present study. 6 The present study indicates that contractions of the rat aorta mediated by intracellular Ca2+ are resistant to the hypoxic conditions studied in the present investigation, whereas those responses mediated by an influx of Ca2+ are reduced. The increase in the contractile response to NA following re-oxygenation may result from an increased influx of extracellular Ca2+ since such responses show an enhanced sensitivity to diltiazem.

An investigation of medicines returned to general practitioners and community pharmacies

Focal points

The use of proprietary medicines by patients presenting with peptic ulcer haemorrhage

1. Medication, social and symptom histories were compared in patients with severe haemorrhage from a peptic ulcer (n = 71) and matched control subjects. Self-medication with proprietary agents was catalogued in addition to therapy prescribed by general medical practitioners. 2. Prior to the bleed, only 4% of ulcer patients had been free of symptoms normally associated with peptic ulceration, whereas 76% of the control group had been asymptomatic. 3. Gastro-irritant proprietary medicines were used regularly by 23% of ulcer patients compared with only 4% of controls. However, proprietary antacids were used chronically by 46% of ulcer patients compared with only 7% of controls. Bicarbonate was the antacid of choice used by 13% of ulcer patients. The odds ratio for the association between development of bleeding peptic ulcer and the use of indigestion remedies was 11.5% (95% CI 1.1, 121). 4. Fifty-one percent of ulcer patients were prescribed agents known to cause gastro-intestinal damage, whereas only 25% of the control group were prescribed similar agents. Only 7% of the control group were prescribed anti-ulcer therapy compared with 37% of those with bleeding ulcer. 5. A large proportion of patients with haemorrhage from a peptic ulcer had had symptoms sufficient to warrant recourse to self-medication with antacids without medical knowledge. Exacerbation of peptic ulcer by self-medication with proprietary products is likely to be of lesser significance.

Community pharmacist perceptions of the loss of resale price maintenance

Focal points

An evaluation of quinolone prescribing in a group of acute hospitals: development of an objective measure of usage

OBJECTIVES

To develop an objective measure to enable hospital Trusts to compare their use of antibiotics.

DESIGN

Self-completion, postal questionnaire with telephone follow up.

SAMPLE

4 hospital trusts in the English Midlands.

RESULTS

The survey showed that it was possible to collect data concerning the number of Defined Daily Doses (DDD's) of quinolone antibiotic dispensed per Finished Consultant Episode (FCE) in each Trust. In the 4 trusts studied the mean DDD/FCE was 0.197 (range 0.117 to 0.258). This indicates that based on a typical course length of 5 days, 3.9% of patient episodes resulted in the prescription of a quinolone antibiotic. Antibiotic prescribing control measures in each Trust were found to be comparable.

CONCLUSION

The measure will enable Trusts to objectively compare their usage of quinolone antibiotics and use this information to carry out clinical audit should differences be recorded. This is likely to be applicable to other groups of antibiotics.

Patient knowledge and acceptability of topical corticosteroid preparations: the role of the pharmacist in patient education

Focal points

Antibiotic prescribing control by pharmacists within UK NHS hospitals

Objective

To identify the role of clinical pharmacists in antibiotic prescribing control.

Method

A self-completion postal questionnaire was sent to the chief pharmacist at 465 UK National Health Service hospitals in 2001/2002. It contained questions covering hospital demographics and the role of pharmacists in ensuring adherence with the recommendations on antibiotic prescribing contained in hospital prescribing documents.

Key findings

Fifty-four per cent of questionnaires (n=253) were completed. Of these, 93% (n=235) of the responding hospitals had at least one of the following prescribing control documents: antibiotic formulary, antibiotic policy and antibiotic guidelines. Pharmacists routinely performed clinical review of adherence with prescribing recommendations (antibiotic prescribing control) in 83% of the responding hospitals but only in approximately two-thirds of hospitals (64%) was this review performed on every ward. The antibiotic prescribing control process appeared to be thorough, with five review activities performed by pharmacists in the majority of hospitals (74%), and proactive, with pharmacists undertaking routine daily visits to all wards (or selected units) in 85% of responding hospitals. Nearly three-quarters (71%) of hospitals had performed an audit of antibiotic prescribing; the majority had done so within the past two years. Pharmacists had been involved in these audits in 92% of responding hospitals.

Conclusions

Where performed, antibiotic prescribing control appeared to be a thorough process. Key areas for service improvement are extension of antibiotic prescribing control to all wards and the standardisation of intervention documentation. Barriers preventing the provision of a comprehensive clinical pharmacy service are discussed and future strategies identified.

Infant Escherichia coli urinary tract infection: is it associated with meningitis?

OBJECTIVES

Determine the prevalence of coexisting bacterial meningitis (BM) and sterile cerebrospinal fluid (CSF) with raised white cell count relative to age ('pleocytosis') in the presence of Escherichia coli urinary tract infection (UTI), with the addition of CSF E. coli PCR analysis.

DESIGN

Single-centre, retrospective cohort study.

SETTING

Tertiary paediatric hospital.

PARTICIPANTS

Children aged 8 days to 2 years, with a pure growth of E. coli from urine and a CSF sample taken within 48 hours of a positive urine culture between 1 January 2014 and 30 April 2019.

MAIN OUTCOME MEASURE

Prevalence of coexisting E. coli BM with UTI, defined as a pure growth E. coli from urine and a CSF culture with pure growth E. coli and/or positive E. coli PCR.

RESULTS

1903 patients had an E. coli UTI, of which 314 (16%) had a CSF sample taken within 48 hours. No cases of coexisting E. coli BM were identified. There were 71 (23%) cases of pleocytosis, 57 (80%) of these had PCR analysis, all of which were E. coli PCR not detected. Patients aged 1-6 months accounted for 72% of all lumbar punctures (LPs).

CONCLUSION

The risk of E. coli UTI and coexisting E. coli BM is low. There is potential to reduce the number of routine LPs in infants with a diagnosis of E. coli UTI with the greatest impact in children up to 6 months of age. CSF E. coli PCR can help further reduce post-test probability of BM in the setting of pleocytosis.

Proton pump inhibitor prescribing following endoscopic diagnosis in a district general hospital

Focal points

Warfarin toxicity: do discharge ICD-10 codes and yellow cards accurately identify serious adverse drug reactions?

Focal points

Risk assessment of intravenous dose presentation in secondary care

Focal points

Polypharmacy and asynchronous prescribing in elderly patients within primary care

Focal points

Antibiotic prescribing for lower respiratory tract infections within secondary care

Focal points

Are community pharmacists prepared to work extended opening hours?

Focal points

Set-up and maintenance of syringe drivers for subcutaneous drug administration in palliative care

Focal points