Pentamidine isethionate. A review of its antiprotozoal activity, pharmacokinetic properties and therapeutic use in Pneumocystis carinii pneumonia

Pentamidine isethionate, an aromatic diamidine, is an antiprotozoal agent proven to decrease mortality from Pneumocystis carinii pneumonia in debilitated infants and immunodeficient adults and children. Like the combination antimicrobial agent co-trimoxazole, pentamidine has been shown in retrospective studies to resolve episodes of pneumonia in approximately 41 to 87% of patients, including those with the acquired immunodeficiency syndrome (AIDS), when used alone or as sequential therapy. Although about 45% of all patients given pentamidine experience side effects--which may include nephrotoxicity, hypotension, hypoglycaemia or local reactions--in patients with AIDS the incidence of side effects is less with pentamidine than with co-trimoxazole. Thus, despite its profile of potentially severe side effects, pentamidine isethionate is a proven antimicrobial agent with a distinct place in the treatment of Pneumocystis carinii pneumonia in the growing population of AIDS patients.     

Piracetam. An overview of its pharmacological properties and a review of its therapeutic use in senile cognitive disorders.

Piracetam is the first of the so-called 'nootropic' drugs, a unique class of drugs which affect mental function. In animal models and in healthy volunteers, the drug improves the efficiency of the higher telencephalic functions of the brain involved in cognitive processes such as learning and memory. The pharmacology of piracetam is unusual because it protects against various physical and chemical insults applied to the brain. It facilitates learning and memory in healthy animals and in animals whose brain function has been compromised, and it enhances interhemispheric transfer of information via callosal transmission. At the same time, even in relatively high dosages it is devoid of any sedative, analeptic or autonomic activities. How piracetam exerts its effects on memory disorders is still under investigation, although among other proposed mechanisms of action it is thought to facilitate central nervous system efficiency of cholinergic neurotransmission. Results from trials involving elderly patients with senile cognitive disorders have been equivocal, as have the results obtained when piracetam has been combined with acetylcholine precursors. Piracetam seems to be almost completely devoid of adverse effects, and is extremely well tolerated. In conclusion, opinion is divided as to the benefits of piracetam in the treatment of senile cognitive decline. Although double-blind studies in the elderly have produced mixed results, some such trials (particularly those involving larger numbers of patients) have reported favourable findings, thus offering some reason for cautious optimism in a notoriously difficult area of therapeutics. However, further investigations of piracetam alone and in combination therapy are required before any absolute conclusions can be drawn.     

Amiodarone. An overview of its pharmacological properties, and review of its therapeutic use in cardiac arrhythmias.

Amiodarone, originally developed over 20 years ago, is a potent antiarrhythmic drug with the actions of all antiarrhythmic drug classes. It has been successfully used in the treatment of symptomatic and life-threatening ventricular arrhythmias and symptomatic supraventricular arrhythmias. In patients with left ventricular dysfunction amiodarone does not usually produce any clinically significant cardiodepression and the drug has relatively high antiarrhythmic efficacy. Preliminary studies indicate that amiodarone may have a beneficial effect on mortality and survival in certain groups of patients with ventricular arrhythmias, an action probably related to both its antiarrhythmic and antifibrillatory effects. The adverse effect profile of amiodarone is diverse, involving the cardiac, thyroid, pulmonary, hepatic, gastrointestinal, ocular, neurological and dermatological systems. Interstitial pneumonitis and hepatitis are potentially fatal, but the vast majority of adverse events are less serious, and some may be dose dependent. Pretreatment monitoring, regular assessments and the use of minimum effective doses are, therefore, necessary. Thus, with appropriate monitoring to control its well recognised adverse effects amiodarone has an important place as an effective 'broad spectrum' antiarrhythmic drug which has, so far, been used when other treatments have proved ineffective. More recent preliminary data also suggest that it may also have a beneficial effect in the prevention of sudden death in some patients.     

Clomipramine. An overview of its pharmacological properties and a review of its therapeutic use in obsessive compulsive disorder and panic disorder

During the 20 years that have elapsed since clomipramine (chlorimipramine) was first marketed, it has become well established in the treatment of depressive illness, particularly treatment-resistant depression. However, in addition to its role as an antidepressant, attention is being focused on the use of clomipramine in 2 other areas of psychiatry: obsessive compulsive disorder and panic disorder. Short term clinical trials have shown that clomipramine is generally more effective than amitriptyline, imipramine, desipramine, nortriptyline or clorgiline in reducing obsessive compulsive symptoms. Clomipramine appears to produce some short term benefit with exposure therapy in patients with obsessive compulsive disorder. However, the efficacy of the drug after long term follow-up has not been fully investigated. The antiobsessional efficacy of clomipramine appears to be independent of its antidepressant activity. In patients with panic disorder with or without agoraphobia (DSM-IIIR), clomipramine reduces the frequency and severity of panic attacks within 7 to 21 days of beginning treatment and efficacy is maintained for at least 12 months. Clomipramine is more effective than imipramine, the generally accepted standard treatment for patients with panic disorder after 2 weeks' treatment, but after 6 or 10 weeks both drugs are similarly effective. Other double-blind studies have shown that clomipramine is more effective than placebo and at least as effective as fluvoxamine and oxitriptan (5-hydroxytryptophan) in reducing panic attacks and associated anxiety. Adverse effects associated with clomipramine treatment are mild to moderate in nature and are predominantly a result of the drug's anticholinergic activity. The incidence of seizures is dose related, occurring in 0.48% of all patients receiving clomipramine less than or equal to 250 mg/day and 2.1% of patients receiving greater than or equal to 300 mg/day. In conclusion, the available data indicate that clomipramine is a worthwhile addition to the limited treatments available for obsessive compulsive disorder and panic disorder, two psychiatric disorders which have previously been difficult to manage pharmacologically.     

Update on pentamidine for the treatment of Pneumocystis carinii pneumonia

The chemistry, spectrum of activity, mechanism of action, pharmacokinetics, adverse effects, and dosage and administration of pentamidine are reviewed, and the role of the drug in treating Pneumocystis carinii infections in immunocompromised patients is discussed. Pentamidine isethionate, an aromatic diamidine compound, is active against certain protozoan organisms. Used extensively in the tropics in the treatment of Trypanosoma and Leishmania infections, its value in the management of Pneumocystis carinii infections has been demonstrated in infected immunosuppressed children and adults. Recently, interest in pentamidine has increased with the rising number of patients with acquired immunodeficiency syndrome (AIDS) who have P. carinii pneumonia. Pentamidine's mechanism of action and pharmacokinetic profile are not completely understood. Pentamidine is distributed extensively after i.v. or i.m. administration, with a volume of distribution of 3 L/kg. Appreciable quantities of pentamidine concentrate in the urine, and drug levels are detectable for up to six to eight weeks after cessation of therapy. After aerosol administration, the drug is almost exclusively recovered from the lung, with little extrapulmonary distribution. Available data suggest that approximately 50% of patients who receive the drug by the i.v. or i.m. route will experience some drug toxicity (local pain, sterile abscesses at the intramuscular injection site, hypoglycemia, hypotension, or azotemia), while adverse effects after aerosol therapy include bronchial irritation but little systemic toxicity. Regardless of the route of administration, pentamidine has emerged as a mainstay of therapy in the management of P. carinii pneumonitis in AIDS patients, especially in those who are allergic to the sulfa component of trimethoprim-sulfamethoxazole.     

Glipizide: a review of its pharmacological properties and therapeutic use.

Glipizide is a 'second generation' oral hypoglycaemic agent similar in potency to glibenclamide. It is completely absorbed after oral administration and has a rapid onset of action, but the duration of its hypoglycaemic effect is shorter than that of glibenclamide. It is rapidly metabolised to inactive metabolites which are excreted in the urine. Therapeutic trials have shown the efficacy of glipizide in maturity onset diabetes mellitus to be comparable with that of glibenclamide and chlorpropamide in newly diagnosed patients unresponsive to diet as well as in patients previously treated with oral hypoglycaemic drugs. Glipizide is well tolerated, but careful adjustment of dosage and attention to diet may be needed to avoid hypoglycaemic symptoms a few hours after a single daily dose.     

Verapamil: a review of its pharmacological properties and therapeutic use.

Verapamil is a novel antiarrhythmic and antianginal agent which, although introduced in 1962, has only recently gained prominence not only as a significant agent in cardiovascular therapeutics but also as a powerful tool to examine the nature of some of the biophysical phenomena at the membrane of cardiac and other excitable tissues. Verapamil is the prototype of those agents which selectively inhibit membrane transport of calcium, an action which accounts for the drug's peripheral and coronary vasodilator properties, its effect on excitation-contraction coupling and hence its negative inotropic propensity, as well as its depressant effects on the sinus node and atrioventricular conduction. Its pharmacological effects are largely independent of the autonomic nervous system. The main therapeutic uses of the drug are in the management of atrial tachyarrhythmias, angina, and possibly hypertension. The overall exp:rimental and clinical data suggest that verapamil will become an important and safe addition to existing drug regimens, especially as an agent of choice for the short-term treatment of most cases of paroxysmal supraventricular tachycardias. The initial experience in other arrhythmias, angina and hypertension, is also sufficiently encouraging to justify further detailed clinical trials to define its potential role in cardiovascular therapeutics.     

Sufentanil. A review of its pharmacological properties and therapeutic use

Sufentanil, an opioid analgesic, is an analogue of fentanyl, and has been used for the induction and maintenance of anaesthesia, and for postsurgical analgesia. It has shorter distribution and elimination half-lives, and is a more potent analgesic than fentanyl. In clinical practice, however, intravenously administered sufentanil produces essentially equivalent anaesthesia to fentanyl and is a better anaesthetic than morphine or pethidine (meperidine) for major surgery. It would appear to maintain haemodynamic stability during surgery better than other opioids or inhalational anaesthetics. Postoperative respiratory depression has been reported in a few patients. For outpatient surgery, intravenous sufentanil produces equivalent anaesthesia to isoflurane or fentanyl. Recovery tends to be more rapid after sufentanil and the requirement for postoperative analgesia is less. Initial clinical trials with sufentanil administered epidurally to relieve pain during labour have produced encouraging results, but further studies are required to establish the drug's role in this indication. Epidural sufentanil produces a more rapid onset and better initial quality of analgesia than morphine, buprenorphine or hydromorphine when administered postoperatively, but the duration of analgesia is shorter. Thus, sufentanil's primary place in therapy at this time would appear to be as high dose anaesthesia for major surgery such as cardiac surgery, and as low dose supplement to balanced anaesthesia in general surgery. In addition, low doses administered epidurally seem to have a potential role for analgesia during labour or after surgery although further studies are required to clarify this situation.     

Nabilone. A preliminary review of its pharmacological properties and therapeutic use

Nabilone is a new orally active cannabinoid for the treatment of severe gastrointestinal toxicity associated with cancer chemotherapy. The pharmacological profile of nabilone suggests that it acts primarily by preventing emesis controlled by the medulla oblongata, although its secondary mild anxiolytic activity may contribute to the overall efficacy. Nabilone 2mg twice daily starting 12 hours prior to, and continued for the duration of, chemotherapy produces significant reduction in the severity and duration of nausea and the frequency of vomiting in about 50 to 70% of patients with severe symptoms refractory to conventional therapy. Nabilone has proven to be more effective in controlling symptoms and preferred by more patients than prochlorperazine 10mg 2 to 4 times daily in a limited number of studies, despite a higher incidence of side effects. Comparative trials against other new antiemetic agents, such as high dose metoclopramide, and use of nabilone in combination with other antiemetics remain to be undertaken. The incidence of side effects is high with nabilone; drowsiness, dizziness and/or vertigo occur in 60 to 70% of patients, but rarely lead to drug withdrawal, although more troublesome effects, such as postural hypotension, ataxia, vision disturbance and toxic psychoses, may cause discontinuation of therapy. Thus, nabilone offers an effective alternative to the treatment options available in a difficult therapeutic area - those patients with severe gastrointestinal side effects from cancer chemotherapy who are refractory to conventional therapy.     

Milrinone. A preliminary review of its pharmacological properties and therapeutic use

Milrinone is a bipyridine derivative of amrinone, with approximately 10 to 75 times greater positive inotropic potency, and separate direct vasodilatory properties. As with amrinone, the relative importance of these properties to treatment of congestive heart failure still remain controversial. The mode of action of milrinone appears to be due in part to selective inhibition of a specific cardiac phosphodiesterase with a subsequent increase in intracellular cyclic adenosine monophosphate and alteration in intracellular and extracellular calcium transport. Clinical experience has involved both short and long term treatment of a limited number of patients with moderate to severe congestive heart failure refractory to conventional therapy. Milrinone has usually been administered as intravenous bolus doses (12.5 to 75 micrograms/kg) and/or continuous intravenous infusion (0.5 microgram/kg/min), or orally (30 to 40 mg/day in divided doses). Milrinone rapidly improves cardiac performance by enhancing myocardial contractility, and by decreasing systemic vascular resistance (afterload), left ventricular filling pressure (preload), and pulmonary arterial pressure. Exercise performance improvement occurs with enhancement of left ventricular performance but without a significant increase in myocardial oxygen consumption or significant decrease in mean arterial pressure. Milrinone has been compared with dobutamine, nitroprusside and captopril in preliminary short term studies in patients with severe congestive heart failure. Milrinone significantly increased stroke work index and decreased left ventricular filling pressure compared to nitroprusside. When compared with dobutamine, both drugs improved cardiac index (to a similar degree), but milrinone significantly reduced right atrial pressure, pulmonary capillary wedge pressure and left ventricular end-diastolic pressure. One small study suggests that short term effects of intravenous milrinone may be superior to those of oral captopril, and it appears that the addition of captopril to milrinone therapy may produce a synergistic haemodynamic effect. Preliminary long term studies suggest that tolerance to the haemodynamic effects of milrinone does not occur, and that the drug is well tolerated and without the thrombocytopenic effects, fever and gastrointestinal complications observed with amrinone. However, it has not been demonstrated that milrinone improves the prognosis of the disease or the overall mortality and its propensity to produce arrhythmias has not been fully agreed upon.(ABSTRACT TRUNCATED AT 400 WORDS)     

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.     

Flurbiprofen: a review of its pharmacological properties and therapeutic use in rheumatic diseases.

Flurbiprofen, a phenylalkanoic acid derivative, is a non-steroidal anti-inflammatory, antipyretic, analgesic agent advocated for use in rheumatoid arthritis, degenerative joint disease, ankylosing spondylitis and allied conditions. Published data suggest that flurbiprofen 120 to 150 mg daily is comparable in effectiveness with therapeutic doses of aspirin (3 to 4 g) in rheumatoid arthritis, but generally causes fewer side effects. Flurbiprofen 150 to 300 mg appears to be comparable with 75 to 150 mg of indomethacin in rheumatoid arthritis and degenerative joint disease, and comparable with phenylbutazone or indomethacin in ankylosing spondylitis. In comparison with other non-steroidal agents, flurbiprofen appears to be at least as effective as naproxen, ibuprofen or sulindac, but generally causes more side effects than these drugs. However, as no one of the non-steroidal anti-inflammatory agents is the most suitable drug for all patients requiring such therapy, flurbiprofen should be considered along with other drugs of its type in the arthritic patient.     

Clobazam: a review of its pharmacological properties and therapeutic use in anxiety

Clobazam1 is a 1,5-benzodiazepine with antianxiety and anticonvulsant properties, advocated for the treatment of primary anxiety and that associated with organic or functional disorders. Clobazam itself has a half-life of 18 hours, but that of the principal metabolite, N-desmethylclobazam, is about 50 hours. Although the metabolite is pharmacologically less active than the parent drug, steady-state plasma concentrations of the metabolite are 8 times higher than those of the unchanged drug. Therapeutic trials indicate that the antianxiety effect of clobazam 30 to 80 mg daily is comparable with that of half its dose of diazepam. Clobazam has minimal muscle relaxant and hypnotic activity. Although subjective drowsiness has occurred with similar frequency with clobazam and diazepam in some studies, clobazam causes less objectively measured sedation or psychomotor impairment in experimental studies. Results of studies of vigilance and psychomotor performance during therapeutic use in patients are less conclusive, but clobazam may be useful in anxious patients who experience such impairment with other benzodiazepines.     

Terfenadine. An updated review of its pharmacological properties and therapeutic efficacy

Terfenadine is a selective histamine H1-receptor antagonist which, in pharmacodynamic studies, is devoid of central nervous system depressant activity. In clinical studies terfenadine is well tolerated and at a dose of 60mg administered twice daily the drug provides effective relief of symptoms in patients with allergic rhinitis (seasonal and perennial), allergic dermatological conditions (particularly chronic urticaria), and other histamine-mediated disorders. Terfenadine is superior to placebo, has a more rapid onset of action than astemizole and is as effective as most other histamine H1-receptor antagonists, in relieving rhinitis symptoms. In allergic rhinitis, terfenadine relieves ocular symptoms to a greater extent (but nasal symptoms to a lesser extent) than inhaled corticosteroids. Administration of oral terfenadine with inhaled sodium cromoglycate (cromolyn sodium) or an inhaled corticosteroid appears more effective than terfenadine alone. Despite the absence of CNS depressant activity in pharmacodynamic studies, sedation is the adverse effect most frequently associated with terfenadine treatment. However, it is important to realise that the incidence of this adverse effect is similar in terfenadine and placebo recipients, and is less frequent than with traditional histamine H1-receptor antagonists. In conclusion, terfenadine is a clinically effective antihistamine which has an improved adverse effect profile compared with classic histamine H1-receptor antagonists. Like other nonsedating antihistamines, it can be considered as a first-line agent in the treatment of allergic rhinitis and chronic urticaria. With additional clinical experience, the drug could find a similar role in other disorders in which a histamine H1-receptor antagonist is indicated.     

Benzbromarone: a review of its pharmacological properties and therapeutic use in gout and hyperuricaemia.

Benzbromarone1 is a benzofuran derivative which lowers serum urate and increases urinary urate excretion in normal, hyperuricaemic and gouty subjects. In open short- and long-term studies benzbromarone reduced serum uric acid levels by one-third to one-half and maintained its effectiveness for periods of up to 8 years. Single-dose experimental studies have shown benzbromarone to have a urate-lowering effect similar to that of a therapeutic dose of probenecid or sulphinpyrazone, but unlike these drugs benzbromarone can be administered in a once daily regimen. In 2 short-term comparative therapeutic trials in a small number of patients with hyperuricaemia, 80mg of micronised benzbromarone daily was at least as effective as 1000mg of probenecid or 300mg of allopurinol daily in lowering serum uric acid levels. Side-effects during benzbromarone administration are usually mild and primarily gastrointestinal in nature.     

Cefuroxime: a review of its antibacterial activity, pharmacological properties and therapeutic use.

Cefuroxime is a new semisynthetic cephalosporin for parenteral administration. It is resistant to destruction by beta-lactamases produced by staphylococci and most Gram-negative aerobic bacteria and is active against many bacteria resistant to cephalothin. Cefuroxime is the most active of the cephalosporins against gonococci and Haemophilus influenzae particularly against beta-lactamase producing strains. Given by intramuscular or intravenous injection cefuroxime is effective against a wide variety of infections caused by Gram-positive or Gram-negative aerobes, but has no effect against infections caused by Pseudomonas aeruginosa or B. fragilis. Cefuroxime is of value in the treatment of respiratory infections due to Haemophilus influenzae and Streptocococcus pneumoniae and is useful against cephalosporin-resistant Klebsiella and Enterobacter infections. Cefuroxime is an alternative to spectinomycin for the treatment of beta-lactamase producing Neisseria gonorrhoeae infections. It is generally well tolerated and appears not to be nephrotoxic when given alone at usual dosages.     

Clozapine. A review of its pharmacological properties, and therapeutic use in schizophrenia

Clozapine, an antipsychotic agent of the dibenzodiazepine class, is characterised by relatively weak central dopaminergic activity and displays atypical pharmacological and clinical properties in relation to the classic antipsychotics. Clinical studies have shown clozapine to be effective in suppressing both the positive and negative symptoms of schizophrenia and to be associated with an extremely low incidence of extrapyramidal side effects. Clozapine has been shown to be of comparable, or on some criteria superior, therapeutic efficacy to perphenazine, levomepromazine, haloperidol and chlorpromazine in several short term comparative studies in patients with schizophrenia of predominantly acute symptomatology. Moreover, clozapine is effective in a substantial proportion (30 to 50%) of schizophrenic patients who are refractory to or intolerant of classic antipsychotic therapy. Despite its promising therapeutic potential, the relatively high incidence of clozapine-induced agranulocytosis (1 to 2% of patients) is a major factor restricting the drug's wider use in psychiatric practice. In accordance with current guidelines, clozapine therapy, performed in conjunction with close haematological monitoring, is indicated for the management of severe and chronic schizophrenia refractory to classic antipsychotic therapy, and in those unable to tolerate such therapy. In such appropriately selected patients, clozapine represents an important alternative to the classic antipsychotics.     

Disopyramide: a review of its pharmacological properties and therapeutic use in treating cardiac arrhythmias.

Disopyramide is a new antiarrhythmic drug with a pharmacological profile of action similar to that of quinidine and procainamide. In a few controlled therapeutic trails and a large number of uncontrolled studies in patients with arrhythmias, often following a myocardial infarction, disopyramide has been relatively effective (more so in ventricular than in atrial arrhythmias) and usually well tolerated. In treating premature atrial and ventricular contractions, the best-studied area of its therapeutic use, disopyramide was superior to a placebo and of similar efficacy to but better tolerated than quinidine; the drop-out rate due to adverse effects of the disopyramide group (10%) being less than one-third that of the quinidine group (36%). In an open ward setting, disopyramide used prophylactically after myocardial infarction appeared to reduce both the incidence of reinfarction and the mortality rate, while in patients treated in coronary care units although the incidence of reinfarction was lower with disopyramide than with a placebo, the mortality rate was not significantly different. Further well-designed trials with adequate numbers of patients are needed before the routine use of disopyramide in infarct patients treated in either setting can be justified. Comparative studies are also required to determine if disopyramide has advantages over other antiarrhythmic agents in this area of use. Side-effects with disopyramide are usually a result of its anticholinergic activity, a dry mouth and difficulty in urination being the most common. Like other antiarrhythmic agents, disopyramide exerts a negative inotropic action on cardiac muscle, and development of acute heart failure has been reported. Development of worsening of heart block and hypotension have also occurred. Disopyramide is largely excreted unchanged and dosage should be reduced in patients with impaired renal function, in accordance with creatinine clearance values.