Wider Clinical Experience Research Articles

Itraconazole

Itraconazole is an orally active triazole antifungal drug which has demonstrated a broad spectrum of activity and a favourable pharmacokinetic profile. It is a potent inhibitor of most human fungal pathogens including Aspergillus sp. In non-comparative clinical trials itraconazole was shown to be extremely effective in a wide range of superficial and more serious 'deep' fungal infections when administered once or twice daily. Generally, greater than 80% of patients with superficial dermatophyte or yeast infections are cured by itraconazole. Similarly, good to excellent response rates (clinical cure or marked improvement) are achieved in paracoccidioidomycosis, histoplasmosis, sporotrichosis, blastomycosis, systemic candidiasis, coccidioidomycosis, chromomycosis, aspergillosis and cryptococcosis. Understandably, given the rare nature of some of these diseases, clinical experience is relatively limited and further evaluation, preferably controlled trials with amphotericin B and ketoconazole, would help clarify the ultimate role itraconazole will have in their management. Preliminary findings also indicate that itraconazole may hold promise for the prophylaxis of opportunistic fungal infections in patients at risk, for example women with chronic recurrent vaginal candidiasis, immunodeficient patients with chronic mucocutaneous candidiasis, AIDS patients and patients receiving immunosuppressant drugs. In studies to date itraconazole has been very well tolerated. Transient changes in indices of liver function occurred in 1 to 2% of patients; however, symptomatic liver dysfunction (as occurs infrequently with ketoconazole) has not been reported. Wider clinical experience is needed to permit clear conclusions as to whether liver dysfunction can result from itraconazole administration. Thus, while several aspects of the drug's profile require further investigation, itraconazole is a promising new oral treatment of fungal disease. The extent to which itraconazole will be employed in preference to ketoconazole will be clarified by wider clinical experience.

Famotidine. Pharmacodynamic and pharmacokinetic properties and a preliminary review of its therapeutic use in peptic ulcer disease and Zollinger-Ellison syndrome.

Famotidine is a new histamine H2-receptor antagonist. On a weight basis, famotidine is 20 times more potent than cimetidine and 7.5 times more potent than ranitidine in inhibiting basal and pentagastrin-stimulated gastric acid secretion in humans. Therapeutic trials have shown that famotidine 20 mg twice daily or 40 mg at bedtime may be an effective alternative to standard doses of cimetidine for healing gastric ulcers and to standard doses of cimetidine and ranitidine for healing duodenal ulcers. When used prophylactically, a single 20 mg dose of famotidine at night decreases the incidence of duodenal ulcer recurrence (versus placebo). However, further study is needed to clarify the comparative efficacy of the H2-receptor antagonists, in particular as maintenance therapy for healed peptic ulcer. Preliminary results in a few patients with Zollinger-Ellison syndrome indicate that famotidine, alone or in combination with an anticholinergic agent, gives good control of gastric acid hyperacidity with no evidence of biochemical or haematological toxicity. Famotidine appears to be well tolerated. Unlike cimetidine, it does not have antiandrogenic effects or alter hepatic metabolism of drugs. However, wider clinical experience with famotidine is needed to accurately determine its relative tolerability compared with other anti-ulcer drugs. Thus, famotidine appears to be a suitable and well tolerated alternative to cimetidine and ranitidine for healing peptic ulcers, but wider clinical experience is needed to assess its relative efficacy and tolerability in the long term maintenance treatment of patients with healed ulcers as well as in patients with Zollinger-Ellison syndrome.

Piretanide. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy.

Piretanide is a potent 'loop' diuretic whose principal site of action is in the thick ascending limb of the loop of Henle. When administered orally or intravenously to healthy volunteers it rapidly increases diuresis and electrolyte excretion, and the effects are short-lived. In comparative studies, piretanide has generally been found to be 5 to 7 times more potent than frusemide (furosemide) but only one-tenth as potent as bumetanide, on a weight-for-weight basis. Piretanide 6 to 12 mg/day, in conventional or sustained release formulations, has been shown to significantly lower elevated blood pressure in a large proportion of patients with mild to moderate hypertension. Comparative trials of up to 3 months duration indicate that at this dosage piretanide is of comparable antihypertensive efficacy as hydrochlorothiazide 50 to 100 mg/day, but has significantly less effect on serum potassium levels. Short term studies in patients with oedema caused by renal, hepatic or cardiac failure demonstrated that piretanide 6 to 9 mg is of similar diuretic potency as frusemide 40 mg and bumetanide 1 mg. In medium term trials in patients with congestive heart failure piretanide 6 mg/day produced equivalent symptomatic improvement as frusemide 40 mg/day. When used to treat oedema caused by liver disease, piretanide 12 to 24 mg/day was successful in only about 50% of patients, but spironolactone added to the treatment regimen greatly increased the response rate. Generally, piretanide has been well-tolerated in clinical trials, although the conventional tablet formulation has caused a relatively high incidence of acute adverse effects--these were greatly reduced with the introduction of the sustained release formulation. Serum concentrations of most electrolytes have not shown any consistent adverse trends and hyperuricaemia and hypokalaemia have been encountered infrequently. Thus, piretanide appears to offer an effective alternative to other 'loop' diuretics for the treatment of oedematous diseases and to hydrochlorothiazide for the management of mild to moderate hypertension. However, its relative place in therapy remains to be clarified with wider clinical experience.

Amrinone A Preliminary Review of its Pharmacological Properties and Therapeutic Use

Amrinone is a bipyridine derivative with positive inotropic effects and vasodilatory properties. However, in the clinical setting of congestive heart failure, the relative contribution of these factors remains a matter of conjecture. Its mode of action appears to be related to alterations in extracellular and intracellular calcium balance, probably mediated by increased levels of tissue cyclic adenosine monophosphate and possibly involving a sodium-dependent pathway. Clinical experience has mostly been short term and is limited to a relatively small number of patients with severe congestive heart failure, refractory to conventional treatment. Amrinone rapidly improves cardiac performance by decreasing systemic vascular resistance (afterload), decreasing the determinants of left ventricular filling pressure (preload) and improving the cardiac contractility. Improvements in exercise performance and clinical symptomatology occur without an increase in heart rate or decrease in mean arterial pressure. Amrinone has been compared with dopamine, dobutamine, pirbuterol and prazosin in preliminary short terms studies in patients with severe congestive heart failure, although more studies are needed before any relative clinical advantages or disadvantages can be ascribed to amrinone. Initial experience suggests that the addition of vasodilators such as hydralazine and isosorbide dinitrate to amrinone therapy may confer additional haemodynamic benefits. Preliminary medium term studies suggest that tolerance to the haemodynamic effects of amrinone does not usually occur, but long term studies are needed to determine whether amrinone alters the normal progression of the disease and whether overall mortality is affected. Amrinone has usually been administered as intravenous bolus doses (totalling 1.5 to 3.6 mg/kg/day) and/or continuous intravenous infusion, with varied results. Generally, an oral dose greater than the intravenous dose is required to achieve an equivalent level of response. Reversible, usually asymptomatic, thrombocytopenia occurs in about 20% of patients treated with amrinone. Arrhythmias and gastrointestinal disturbances have been reported, but wider clinical experience is required to determine the side effect profile of the drug.

Ranitidine: a review of its pharmacology and therapeutic use in peptic ulcer disease and other allied diseases.

Ranitidine is a new histamine H2-receptor antagonist which, unlike cimetidine, does not contain an imidazole group. On a weight basis, ranitidine is 4 to 10 times more potent than cimetidine in inhibiting stimulated gastric acid secretion in humans. Therapeutic trials comparing ranitidine and cimetidine have demonstrated that ranitidine 150 mg twice daily is an effective alternative to cimetidine 1000 mg daily in 4 divided doses in increasing the rate of healing of duodenal and gastric ulcers over a period of 4 to 6 weeks. Ranitidine, given as a single 150 mg dose at night, decreases the incidence of ulcer recurrence. Preliminary studies in the Zollinger-Ellison syndrome and in patients intolerant of, or unresponsive to cimetidine, indicate that ranitidine controls the gastric hyperacidity and heals most ulcers, including those which failed to respond to months of treatment with cimetidine 1 to 1.6 g daily. Ranitidine, unlike cimetidine, has no antiandrogenic effects and does not alter hepatic metabolism of drugs. Ranitidine is well tolerated. Preliminary reports of the resolution of cimetidine-induced adverse effects following substitution of ranitidine, suggest that ranitidine may be of value in patients intolerant of cimetidine. However, wider clinical experience with ranitidine is needed to determine the clinical relevance of these reports.

Captopril: a preliminary review of its pharmacological properties and therapeutic efficacy.

Captopril is the first orally active inhibitor of angiotensin-converting enzyme to become available. It has been studied primarily in hypertension. In mild to moderate essential hypertension captopril is about as effective as usual doses of hydrochlorothiazide or propranolol, about one-half of such patients needing the addition of a diuretic to achieve satisfactory control of blood pressure. In severe hypertension captopril plus a diuretic (and in some patients a beta-blocker) usually reduced blood pressure significantly more than could be achieved with 'standard triple therapy' in patients not responding adequately to such a regimen, and often resulted in an improved feeling of well-being in severely hypertensive patients previously receiving intensive multiple drug therapy. Indeed, at the present stage of the drug's development, patients not responding to or not tolerating 'traditional' antihypertensive therapy represent the most suitable candidates for captopril treatment. While captopril has been well tolerated in most patients, some troublesome or potentially serious side effects have been reported, including agranulocytosis, dysgeusia and reduced renal function; although a clear causal relationship with captopril was not always established, it would appear that the final place of captopril in the treatment of hypertension may ultimately depend on further clarification of its adverse effects profile. In addition to studies in hypertension, captopril has produced encouraging improvement in a small number of patients with severe congestive heart failure resistant to conventional therapy. Captopril must be considered an exciting addition to the therapeutic armamentarium; it, and pharmacologically related compounds of the future, will continue to generate much interest as their final place in therapy becomes better defined through additional well designed studies and wider clinical experience.

Tobramycin: a review of its antibacterial and pharmacokinetic properties and therapeutic use.

Tobramycin is a new aminoglycoside antibiotic with a broad antibacterial spectrum in vitro, and pharmacokinetic properties similar to those for gentamicin. Tobramycin is more active than gentamicin against Pseudomonas aeruginosa and active against many gentamicin resistant strains, but is not active against enterobacteriaceae resistant to gentamicin. Theoretically, tobramycin has an advantage over gentamicin against infections caused by P. aeruginosa, but any advantage in clinical practice has yet to be adequately demonstrated. Clinical experience with tobramycin is considerably less than with gentamicin. Whilst tobramycin appears to offer no clear advantages over gentamicin against sensitive organisms it is indicated in infection caused by strains of P. aeruginosa which are resistant to gentamicin, but sensitive to tobramycin. Like gentamicin, tobramycin acts synergistically with corbenicillin and the cephalosporins. The efficacy of the tobramycin-carbenicillin combination has been shown in endocarditis caused by P. aeruginosa which was unresponsive to gentamicin plus carbenicillin. Ototoxicity and nephrotoxicity similar to that seen with other animoglycosides have been encountered in therapeutic trials with tobramycin and wider clinical experience is necessary to determine the relative incidence of these side-effects with gentamicin and tobramycin used under similar conditions. Antimicrobial activity: In comparative studies, in vitro, tobramycin is more active than gentamicin against clinical isolates of Pseudomonas aeruginosa. Similarly, the inhibitory index, which is the ratio between the serum concentration attained at usual therapuetic doses and the minimum inhibitory concentration, for Pseudomonas aeruginosa is higher for tobramycin than for gentamicin. Against Gram-negative bacteria other than Pseudomonas spp. the spectrum of activity of tobramycin is similar to that of gentamicin. For most species the activity of tobramycin is slightly less than that of gentamicin. Gentamicin is consistently more active than tobramycin against Serratia marcescens. Like other aminoglycoside antibiotics, tobramycin is active in vitro in low concentrations against Staphylococcus aureus. Tobramycin is essentially inactive against Streptococcus pyogenes, Streptococcus faecalis and Streptococcus pneumoniae (pneumococci). Maner aminoglycosides and of other antibiotics against various bacteria in vitro, but comparisons between studies cannot always be interpreted literally because the activity of many antibiotics in vitro, including tobramycin, is influenced by the nature of the culture media and the presence of certain salts. The sensitivity of P. aeruginosa to tobramycin is influenced by the magnesium, and calcium content of the culture media whilst that of all species is reduced by sodium ions. Wide variations in the concentration of these ions may result in divergent MIC values and an inappropriate choice of antibacterial agent to treat pseudomonas infection...