Rifampicin and anti-hypertensive drugs in chronic kidney disease: Pharmacokinetic interactions and their clinical impact

Patients on dialysis have an increased incidence of tuberculosis (TB). Rifampicin, a first-line antitubercular therapy (ATT) drug, is a potent inducer of hepatic cytochrome P450 (CYP). There is potential for pharmacokinetic interaction between rifampicin and anti-hypertensives that are CYP substrates: amlodipine and metoprolol. Therefore, hypertensive patients receiving rifampicin-based ATT are at risk for worsening of hypertension. However, this hypothesis has not yet been systematically studied. In this prospective study, hypertensive CKD 5D patients with TB were followed after rifampicin initiation. Blood pressure (BP) was ≤140/90 mmHg with stable anti-HT requirement at inclusion. Serum amlodipine, metoprolol, and prazosin levels were estimated by high-performance liquid chromatography at baseline and 3, 7, 10, and 14 days after rifampicin initiation. BP and anti-HT requirement were monitored for 2 weeks or until stabilization. All 24 patients in the study had worsening of hypertension after rifampicin and 83.3% required increase in drugs to maintain BP <140/90 mmHg. Serial amlodipine levels were estimated in 16 patients; metoprolol and prazosin in four patients each. Drug levels declined by >50% in all patients and became undetectable in 50-75%. Drug requirement increased from 4.5 ± 3.6 to 8.5 ± 6.4 units (P < 0.0001). Mean time to first increase in dose was 6.5 ± 3.6 days. Eleven (46%) patients experienced a hypertensive crisis at 9.1 ± 3.8 days. Three of them had a hypertensive emergency with acute pulmonary edema. In two patients, rifampicin had to be discontinued to achieve BP control. In conclusion, rifampicin caused a significant decrease in blood levels of commonly used anti hypertensives. This decrease in levels correlated well with worsening of hypertension. Thus, we suggest very close BP monitoring in CKD patients after rifampicin initiation.

A pilot study on area under curve of mycophenolic acid as a guide for its optimal use in renal transplant recipients

Background & objectives:

The immunosuppressants administered to renal transplant subjects are usually monitored therapeutically to prevent graft rejection and drug toxicity. Mycophenolic acid (MPA) is an immunosuppressant. The present prospective study was undertaken to establish the utility of plasma level monitoring of MPA and to correlate it with clinical outcomes in renal transplant receipients.

Methods:

MPA plasma level at 2, 4 and 9 h and the area under concentration-time curve (AUC) were estimated using high performance liquid chromatography in 24 renal transplant recipients receiving immunosuppressant MPA plus tacrolimus and steroid.

Results:

There was wide inter-individual variation in MPA plasma level and the AUC. The incidences of gastrointestinal adverse drug events (diarrhoea and acidity) were significantly more in the high MPA AUC patients. Though biopsy proven acute rejection was not found, of the six subjects with lower MPA AUC (<30 mg.h/l), three were clinically diagnosed to develop tacrolimus nephrotoxicity. The Gastrointestinal Symptom Rating Scale (GSRS) and Gastrointestinal Quality of Life Index (GIQLI) scores represented better health related quality of life in lower MPA AUC than in the higher MPA AUC (>60 mg.h/l).

Interpretation & conclusions:

The present findings suggest the MPA AUC of 30 - 60 mg.h/l in the maintenance stage of renal transplant patients to have optimum clinical benefit and relegated adverse events profile indicating the usefulness of AUC of MPA with limited sampling strategy in optimizing its use.

Misuse of corticosteroids in some of the drugs dispensed as preparations from alternative systems of medicine in India

Screening for corticosteroids carried out on 120 samples of alternative medicines which were dispensed to patients suffering mainly from asthma, arthritis, etc., showed that 38.32% of them were adulterated with steroids. Most of these samples were submitted for screening by either a medical practitioner or the patients themselves, who suspected effects of steroids from these drugs. The percentage of steroid positivity was determined in ayurvedic drugs, homeopathic drugs, and unknown or other category of drugs. The presence of steroids in these drugs given for different ailments such as asthma, arthritis, and unknown/other ailments was also tabulated. The results show that a high percentage of these samples contained corticosteroids, however, the distribution of positivity amongst groups was not statistically significant. The lack of proper quality control mechanisms to verify ingredients or efficacy of 'alternative medicines' has led to the proliferation of the practice of dispensing spurious drugs containing corticosteroids as alternative medicines. This study aims to highlight the existence of 'quick fix' remedies dispensed as 'alternative medicines' which not only cause extensive adverse health effects to the patients but also bring alternative systems of medicines into disrepute. The deliberate contamination of corticosteroids with alternative systems of medicine by some practitioners is a cause of great concern. Such practices may not only disgrace alternative systems of medicine but may also lead to adverse side-effects on chronic exposure.