Drug administration in renal failure

Effects of renal insufficiency on the pharmacokinetics and pharmacodynamics of opioid analgesics

The disposition and pharmacologic activities of morphine, meperidine, methadone, propoxyphene, dihydrocodeine, and codeine are reviewed. Dose-related toxicities of these opioid analgesics include mental obtundation, respiratory depression, and hypotension. Furthermore, convulsions have been associated with normeperidine and cardiac toxicities with norpropoxyphene. Hepatic metabolism is the primary route of elimination, except for methadone, for which there is also significant renal excretion. Although the pharmacokinetics of morphine are unchanged in renal insufficiency, accumulation of active metabolites may lead to narcosis. Similar accumulation of normeperidine and norpropoxyphene, metabolites of meperidine and propoxyphene, respectively, as well as propoxyphene itself, and dihydrocodeine and codeine may explain reports of adverse reactions in patients with impaired renal function. A high index of suspicion of opioid-induced toxicities should be maintained in patients who have renal dysfunction and receive opioids.

Dihydrocodeine in renal failure: further evidence for an important role of the kidney in the handling of opioid drugs

The pharmacokinetics of a single oral dose of dihydrocodeine were studied in nine patients with chronic renal failure treated by haemodialysis and nine subjects with normal renal function. In the patients the mean peak plasma dihydrocodeine concentration occurred later and the area under the curve was greater than in the normal subjects. Furthermore, the drug was still detectable after 24 hours in all the patients but only three of the normal subjects. These data, together with those obtained from previously published clinical case reports, contradict the traditional view that the body's ability to cope with opioid drugs is not altered in renal failure.

Digoxin-quinidine interaction in patients with renal failure

Investigations were performed in order to study whether or not quinidine would exert similar effects on the serum digoxin concentration in patients with renal failure as in normal subjects. Fourteen out of fifteen patients showed a significant increase of the serum digoxin level after four days of quinidine application. This indicates, that the quinidine effect is not solely caused by a decrease of the renal digoxin clearance, although nine patients, not being hemodialysed, revealed a correlation between their creatinine clearance and the rise of the serum digoxin concentration after quinidine. As however, the patients on hemodialysis did not show higher digoxin levels than those treated conservatively, it is suggested that the degree of the uremic intoxication might be responsible for the observed correlation.

Pharmacokinetics of dihydroquinidine in congestive heart failure patients after intravenous quinidine administration

The pharmacokinetics of dihydroquinidine were studied in 8 patients with congestive heart failure following a 22 min intravenous infusion of a quinidine preparation that contained 5.9% dihydroquinidine as an impurity. Using a thin layer chromatography-fluorometric assay procedure for dihydroquinidine, the post-infusion plasma dihydroquinidine concentrations declined biexponentially. The half-life of the fast and slow dispositional processes was 4.42 +/- 1.81 min and 6.52 +/- 2.40 h, respectively. The central compartment volume for dihydroquinidine in these patients was 0.44 +/- 0.11 l/kg with an overall apparent volume of distribution of 1.14 +/- 0.38 l/kg. The computed values of total body plasma clearance of dihydroquinidine ranged from 1.29 to 2.69 ml/min/kg with a mean value of 1.94 +/- 0.60 ml/min/kg. In these patients, approximately 16% of the administered dihydroquinidine dose was excreted intact into the urine in 48 h. The estimated value of renal clearance was 0.314 +/- 0.129 ml/min/kg. When compared to control cardiac patients, the data showed that the apparent volume of distribution for dihydroquinidine is smaller in patients with congestive heart failure and as a result of this diminished volume, the clearance rate of dihydroquinidine was slower. The net effect of these differences was the production of higher plasma concentrations of dihydroquinidine in the heart failure group.

Biotransformation of diflunisal and renal excretion of its glucuronides in renal insufficiency

1 A single oral dose of 500 mg diflunisal was administered to control subjects and patients with varying degrees of renal insufficiency to estimate the disposition kinetics of this drug.

2 Diflunisal and the sum of its ester and ether glucuronides conjugates were measured fluorimetrically.

3 In normals terminal plasma half-lives (T_½β) of diflunisal and its glucuronides were very similar: 10.8 h and 11.8 h respectively. The finding that plasma half-life was shortened with declining diflunisal plasma levels suggests capacity-limited elimination.

4 In subjects with normal renal function 78.6 ± 2.7% of the administered dose was recovered in 72 h urine, mainly as the glucuronide conjugates.

5 With increasing degree of renal function impairment T_½β of diflunisal was progressively prolonged up to ten times normal probably due to slowed biotransformation. This was associated with increasing retention of the conjugated metabolites in plasma due to marked reduction of the urinary excretion of the glucuronide conjugates.

6 The apparent volume of distribution of diflunisal was very small in normals (7.3 ± 0.4 l) and was significantly increased in patients with renal insufficiency (up to 16.2 ± 2.2 l).

7 Diflunisal elimination studies performed during haemodialysis did not reveal any significant change in diflunisal plasma half-time. In vivo ultrafiltration studies during haemodialysis have shown that diflunisal is 98-99% plasma protein bound in uraemic patients.

8 The present study indicates that although diflunisal is primarily eliminated by biotransformation, T_½β is prolonged in renal insufficiency and dose adjustment will accordingly be required in patients with renal function impairment.