Prednisone and prednisolone are used in a wide variety of diseases. The two compounds are metabolically interconvertible; prednisolone is assumed to be the pharmacologically active species.Prednisone and prednisolone plasma concentrations are commonly determined by either radioimmunoassay or competitive protein binding techniques. No relationship has been demonstrated between prednisolone plasma concentration (unbound or total concentration) and clinical response; alternate day dosage regimens with fluctuating plasma concentrations being considered generally to be as effective with less side effects than a daily dosage regimen.Both drugs are rapidly absorbed after oral administration, reaching peak plasma concentrations after I to 3 hours. In general, plasma half-lives for prednisone are slightly longer (3.4 to 3.8h) than for prednisolone (2.1 to 3.5h). Either drug can be prescribed in most situations. On average, however, the bioavailability of prednisolone after oral prednisone is approximately 80 % of that after prednisolone. A wide intersubject variation in prednisolone concentration is evident after both drugs, which may suggest impaired drug absorption in some individuals. Prednisolone shows dose dependent pharmacokinetics; an increase in dose leading to an increase in volume of distribution and plasma clearance. This can be explained in terms of the non-linear binding of the drug to plasma proteins. The degree of binding will determine the distribution and clearance of free (i.e. pharmacologically active) drug. Reduced doses are recommended in patients with hypoalbuminaemia.Prednisolone pharmacokinetics are also dependent on age; the half-life being shorter in children. Liver disease prolongs the prednisolone half-life and, due to thefrequently associated hypoalbuminaemia, also increases the percentage of unbound drug. It has been recommended by some that prednisolone rather than prednisone is the drug of choice in active liver disease owing to the poor conversion of prednisone to prednisolone in some patients. However, the reduced plasma concentration of prednisolone in such patients is compensated for by delayed clearance. Thus, there is little advantage of one preparation over the other.

C-reactive protein (CRP) levels were measured in 105 patients with rheumatoid arthritis (RA) during treatment with slow-acting anti-rheumatoid drugs D-penicillamine, alclofenac, hydroxychloroquine, gold, sulphasalazine and azathioprine. A control group treated with aspirin alone was also included. Patients were assessed clinically (pain score, articular index and summated change score) and in terms of acute-phase reactants (CRP, haptoglobin, fibrinogen, ESR and plasma viscosity) at eight separate clinic visits during the 6-month treatment period. The estimation of CRP was found to be more useful than haptoglobin, fibrinogen or ESR as an index of disease activity.

No abstract

The pharmacokinetics of prednisolone elimination have been studied in both arthritic patients and normal volunteers using tritiated prednisolone alone, and in conjunction with unlabelled prednisolone in doses of 0.15 mg-kg-1 and 0.3 mg-kg-1 body weight. With increasing dose there is prolongation of the plasma half-life and increase in the volume of distribution and plasma clearance of prednisolone. It is proposed that these changes in pharmacokinetic parameters may be associated with non-linear binding of the steroid to plasma proteins.

The absorption of a range of steroids (water soluble to lipid soluble) in the mouth was investigated under standard conditions and using gas chromatography. A two-compartment open model was used to describe the absorption of these steroids into, and through, the membrane. Rate constants were calculated on this basis using a feathering technique, and were used in an analogue computer program to predict steroid concentration which agree favourably with experimental data. Correlations between absorption and partition data were made in an attempt to relate the proposed model to anatomical features of the absorptive membrane and to make comparison with models proposed to describe drug absorption across the intestinal mucosa.

No abstract

1 Ephedrine plasma levels have been measured in ten asthmatic patients given a singel dose of ephedrine hydrochloride (22 mg) along and in combination with theophylline and a barbiturate. 2 Pharmacokinetic assessment of the data indicated no significant intra‐subject changes in kinetic parameters before or after chronic treatment with ephedrine HCl (11 mg three times a day) alone or in combination. 3 Tolerance to these therapeutic doses, if it occurs, is therefore not disposition‐ related but rather to pharmacodynamic changes.

1 Single-dose studies were conducted to investigate the relative potency of prednisolone and betamethasone in suppressing adrenocortical function. 2 Betamethasone produced more profound suppression of plasma cortisol than an equivalent antiinflammatory dose of prednisolone.