Linear pharmacokinetic behavior of ropinirole during multiple dosing in patients with Parkinson's disease

The objectives of this study were to measure the pharmacokinetics of ropinirole at steady state when the drug is used as an adjunct to L-dopa and evaluate the long-term tolerability of ropinirole in this indication. Twenty-four patients who were taking L-dopa for Parkinson's disease and experiencing a lack of symptomatic control were recruited. Patients received open-label adjunctive treatment with ropinirole for up to 2 years. The starting dose was 0.5 mg bid, which could be titrated to a maximum of 6.0 mg tid. Ropinirole demonstrated approximately dose-linear pharmacokinetics at steady state; corresponding values were higher during tid than bid dosing. A reduction in mean L-dopa dose was maintained throughout the trial. The combination of L-dopa and ropinirole was generally well tolerated, with only 1 patient withdrawing from treatment because of adverse events. Thus, ropinirole shows approximately linear steady-state pharmacokinetics and a good safety profile when administered with L-dopa.

Pharmacokinetics of a hematoregulatory peptide (SK&F107647) in healthy male volunteers and in patients with colorectal or pancreatic adenocarcinoma not amenable to standard therapy

PURPOSE

To describe the pharmacokinetics of SK&F 107647, a synthetic hematoregulatory peptide, in healthy volunteers and in patients with adenocarcinoma.

METHODS

SK&F 107647 pharmacokinetics were evaluated in 2 dose-escalation studies. Volunteers received SK&F 107647 as single 15-minute iv infusion doses of 1, 10, 100, 500, and 1,000 microg/kg. Cancer patients received 2-hour iv infusions of 0.001, 0.01, 0.1 and 1 microg/kg once daily for 10 days. Drug concentrations were quantified in plasma and urine of healthy volunteers and on days 1 and 10 in plasma of cancer patients receiving the two top dose levels.

RESULTS

In volunteers, mean clearance (CL) ranged from 76.7 to 101 ml/hour/kg; mean volume of distribution at steady-state (Vss) ranged from 175 to 268 ml/kg. Most of the administered dose was renally excreted as intact peptide within 24 hours postinfusion. In patients, mean CL was 57.6 ml/hour/kg, mean Vss ranged from 128 to 150 ml/kg and terminal half-life from 2.1 to 3.4 hours. There was little accumulation of drug. In both studies, linear pharmacokinetics was observed. Clearance approached normal glomerular filtration rate (GFR) in volunteers and correlated with creatinine clearance in cancer patients.

CONCLUSIONS

SK&F 107647 exhibits linear pharmacokinetics, a small Vss, and clearance, primarily renal, approaching normal GFR.

Disposition of ropinirole in animals and man

1. The disposition and metabolic fate of ropinirole, a novel compound indicated for the symptomatic treatment of Parkinson's disease, was studied in the mouse, rat, cynomolgus monkey and man, following oral and intravenous administration of ropinirole hydrochloride. 2. In all species, nearly all of the p.o. administered dose (94%) was rapidly absorbed from the gastrointestinal tract following administration of 14C-ropinirole hydrochloride. In rat and monkey, the compound distributed rapidly beyond total body water and was shown to cross the blood-brain barrier. Blood clearance of the compound was high, approximately equal to one-half the hepatic blood flow in the monkey and similar to the hepatic blood flow in rat. Terminal phase elimination half-lives for the compound were relatively short (0.5 and 1.3 h in rat and monkey respectively), although there was evidence of a second elimination phase in the monkey with an elimination half-life of approximately 5-11 h. Plasma concentrations of ropinirole after the intravenous dose were not determined in the mouse and were below the lower limit of quantification in man (0.08 ng/ml) at the doses used in the studies described in this paper. 3. In both animals and man, ropinirole was extensively metabolized. In the rat, the major metabolic pathway was via hydroxylation of the aromatic ring to form 7-hydroxy ropinirole. In mouse, monkey and man, the major pathway was via N-depropylation. The N-despropyl metabolite was metabolized further to form 7-hydroxy and carboxylic acid derivatives. Metabolites formed in all species were generally metabolized further by glucuronidation. 7-Hydroxy ropinirole is the only metabolite of ropinirole previously shown to possess significant dopamine agonist activity in vivo. In all species, the major route of excretion of ropinirole-related material after oral or intravenous administration of the compound was renal (60-90% of dose).

Lack of a pharmacokinetic interaction at steady state between ropinirole and L-dopa in patients with Parkinson's disease

STUDY OBJECTIVE

To assess the interaction between therapeutic dosages of ropinirole and L-dopa plus a decarboxylase inhibitor administered at steady state in patients with Parkinson's disease. DESIGN. Open, 6-week, overlap trial with random allocation.

PATIENTS

Thirty patients with Parkinson's disease not previously treated with dopamine agonists, of whom 28 produced evaluable pharmacokinetic data for ropinirole and 23 for L-dopa.

INTERVENTION

Group A (14 patients) received L-dopa for weeks 1-5 and ropinirole in increasing increments for weeks 2-6; group B (16) received ropinirole for weeks 1-5 and L-dopa for weeks 5 and 6.

MEASUREMENTS AND MAIN RESULTS

Primary end points were AUC0-8 and Cmax for ropinirole, and AUC0-8, AUC0-infinity and Cmax for L-dopa. Secondary end points were Tmax for ropinirole, and Tmax and half-life for L-dopa. Coadministration with L-dopa at steady state did not affect rate or extent of availability of ropinirole: point estimates of the geometric mean ratio for ropinirole plus L-dopa compared with ropinirole alone for both Cmax and AUC0-8 approximated to unity. The small (16%) increase in peak concentrations of L-dopa on administration with ropinirole is unlikely to be of clinical consequence, as peak concentrations of L-dopa are typically highly variable.

CONCLUSION

There are no pharmacokinetic grounds for adjusting dosages of either ropinirole or L-dopa when given in combination.

Effect of food on the pharmacokinetics of ropinirole in parkinsonian patients

AIMS

Ropinirole is a specific non-ergoline dopamine D2-receptor agonist with antiparkinsonian properties. The pharmacokinetic parameters of ropinirole taken in the fasted condition were compared with those when it was co-administered with food.

METHODS

This was an open, randomized, two sessions cross over study in 12 patients with Parkinson's disease, comparing the steady-state pharmacokinetic profiles of ropinirole on two different study days: 'fasted' and 'fed'.

RESULTS

The mean Cmax was lower in the 'fed' regimen than in the 'fasted' one (-25%, P=0.002). The median tmax was observed 2.6 h later in the 'fed' regimen than in the 'fasted' regimen (P<0.05). There was a slight but significant decrease in AUC(0,8 h) in the 'fed' regimen (P=0.03).

CONCLUSIONS

Food decreases the rate of absorption of ropinirole, but has little effect on the extent of absorption.

Interspecies pharmacokinetics of a novel hematoregulatory peptide (SK&F 107647) in rats, dogs, and oncologic patients

PURPOSE

To study the pharmacokinetics of SK&F 107647, a novel hematoregulatory agent, in rats, dogs, and patients with non-lymphoid solid tumor malignancy.

METHODS

Sprague Dawley rats and beagle dogs (n = 6 each; 3 M, 3 F) were given 25 mg/kg of SK&F 107467 as an iv bolus injection, and patients (n = 6; 4 M, 2 F) received 100 mg/kg as a 2 hour iv infusion. Plasma samples were assayed for drug using either HPLC (rat and dog) or RIA (human).

RESULTS

In each species the plasma clearance (CL) of SK&F 107647 was low in relation to hepatic blood flow, and the volume of distribution (Vd ss) was reflective of distribution to extracellular body water. The plasma CL in humans was near that of average glomerular filtration rate. Using allometric equations for interspecies scaling (Y = a.W(b)), body-weight normalized human pharmacokinetic data were reasonably predicted using either the body weight normalized rat or the dog data. The allometric exponents (b) for CL, Vd(ss), and T(1/2) of SK&F 107647 were 0.63, 0.94, and 0.29, respectively.

CONCLUSIONS

Use of a limited pool of available animal data allowed for reasonable predictions of human pharmacokinetics of SK&F 107647.