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Biomedical subjects

L F Gram

Publications and source records attributed to L F Gram.

At least 91 records · Page 5Linked to original sources
PubMed1991

Extremely slow metabolism of amitriptyline but normal metabolism of imipramine and desipramine in an extensive metabolizer of sparteine, debrisoquine, and mephenytoin.

A 34-year-old man with bipolar manic depressive illness suffered from severe adverse effects during treatment with amitriptyline, 50 mg/day. It was subsequently shown that the patient was a slow metabolizer of amitriptyline. However, he tolerated a dose of 200 mg of imipramine/day, which was necessary in order to reach a therapeutic level of about 900 nM for imipramine plus desipramine. Since both antidepressants are subject to the genetic sparteine/debrisoquine oxidation polymorphism, the patient was phenotyped with sparteine. The test performed during paroxetine treatment indicated that the patient was a poor metabolizer. Subsequent tests performed during a drug-free period, however, showed the patient to be an extensive metabolizer, with a sparteine metabolic ratio (MR) of 1.7 and 2.8 and debrisoquine MR of 2.3. It was subsequently shown that paroxetine is a potent, competitive inhibitor of 1'-hydroxybufuralol formation in a human liver microsome preparation (K1 approximately 800 nM). This patient thus illustrates two problems: (a) the erroneous phenotyping due to concurrent medication, and (b) the existence of a very slow amitriptyline elimination apparently not related to the sparteine/debrisoquine oxidation polymorphism.

Administration, Oral↗
PubMed1991

Concentration-response relationship in paroxetine treatment of diabetic neuropathy symptoms: a patient-blinded dose-escalation study.

A single-blind dose-escalation study with the selective serotonin reuptake inhibitor paroxetine was conducted in 19 diabetic patients with neuropathy symptoms. The effect of treatment was evaluated by self-rating using visual analog scales. After an initial placebo period, paroxetine doses were increased from 10 mg/day in 10 mg steps, until the dose was 30-70 mg/day. In all except four patients, there was a marked relief of symptoms. Plasma concentrations of paroxetine above 300-400 nM were required to insure maximal relief in the majority of patients responding on paroxetine, but a considerable interindividual variation was observed (10-800 nM, median of 195 nM). The therapeutic effect appeared to increase gradually as the plasma concentration increased. The great interindividual variation in the pharmacokinetics of paroxetine was confirmed, but as the effect is maximal within approximately 1 week, and the drug is nontoxic, it may be clinically feasible simply to titrate the dose from 20 mg/day until the maximal effect is achieved. However, it is advised that titration to an effect, in diabetic neuropathy using doses above 50 mg/day, be undertaken with care as there is limited experience with doses above this level in any population. The beneficial effect of paroxetine appeared to be maintained unaltered during an additional 1 month open-label treatment on optimal paroxetine doses.

Adult↗
PubMed1991

The activation of the biguanide antimalarial proguanil co-segregates with the mephenytoin oxidation polymorphism--a panel study.

The activation of the antimalarial drug proguanil (PG) to the active metabolite cycloguanil (CG) has been evaluated in a panel of 18 subjects. These subjects had previously been screened and classified as mephenytoin poor (PMm) or extensive metabolisers (EMm) and sparteine poor (PMs) or extensive metabolisers (EMs). Five subjects had the phenotype PMm/EMs, one was PMm/PMs, six subjects were EMm/PMs and six were EMm/EMs. The PG/CG ratio in urine (8 h) was significantly higher in PMm than in EMm (P = 0.0013). This study shows that the P450-isozyme involved in the polymorphic oxidation of mephenytoin is of critical importance in the activation of PG to CG and this may explain the large intersubject variability in CG concentrations in man. PMm make up about 3% of Caucasians, but up to about 20% of Orientals. From the present study, it may be anticipated that the antimalarial effect of PG is absent or impaired in this phenotype. The sparteine polymorphism appeared not to influence the activation of PG to CG significantly.

Adult↗
PubMed1991

Drugs and femoral neck fracture: a case-control study.

Two hundred consecutive patients with femoral neck fractures (FNF) and 200 controls matched by age, sex, nursing home residency and number of admissions within the last 2 years, were interviewed about recent drug use. The matching criteria were chosen to achieve case and control groups that were comparable with regard to overall physical disability. Thus a preliminary study had shown FNF to be strongly associated with nursing home residency and to be correlated with the number of recent hospital admissions. FNF was found to be negatively associated with use of coronary drugs (OR = 0.27; 95% CI = 0.11-0.70) and positively associated with drug use in general (OR = 2.00; 95% CI = 1.04-3.05). The OR for the various classes of psychotropic drugs was consistently greater than 1., although this was not statistically significant. An inherent problem in interpreting such findings is that underlying disease may predispose the subject to both FNF and drug use, thus creating a non-causal relationship.

Aged↗
PubMed1991

Drug-related admissions to a department of medical gastroenterology. The role of self-medicated and prescribed drugs.

Three hundred and twenty-eight consecutive patients admitted to a department of medical gastroenterology were evaluated in a high-intensity study of drug-related hospitalizations (DRH). The drug events considered were adverse drug reaction and dose-related therapeutic failures (DTF). With regards to the 'definite' and 'probable' drug events, DRHs accounted for 26 admissions (7.9%; 95% confidence interval (CI), 5.2-11.4%), and with the additional inclusion of 'possible' drug events DRHs accounted for 39 admissions (11.9%; CI, 8.6-15.9%). Of these, five and seven admissions, respectively, were caused by DTF. Patients admitted because of drug events took significantly more drugs than others. An evaluation of the circumstances of the 26 'definite' or 'probable' DRH showed none to be 'definitely avoidable', 6 to be 'possibly avoidable', and 20 to be 'not avoidable' by efforts from the prescribing physicians. Gastroduodenal lesions causally related to non-steroidal anti-inflammatory drug (NSAID) or aspirin use accounted for 17 of the definite, probable, or possible DRHs (44%). Only 1 of the 11 cases related to NSAID use was rated as possibly avoidable by efforts from the health service personnel. In 13 cases self-medication with aspirin played a substantial role in the DRH. Self-medication was largely characterized by poor indication, uncontrolled use, polypharmacy, treatment of epigastric pain with aspirin, and the patient's unawareness of potential adverse reactions. This suggests the need for intensified information to the public concerning the adverse effects of aspirin and NSAID.

Adult↗
PubMed1991

Drug related events and drug utilization in patients admitted to a geriatric hospital department.

Two hundred ninety-four consecutive admissions to a geriatric department were evaluated for drug events as cause of admission. The drug events considered were adverse drug reactions (ADRs) and dose-related therapeutic failures. In 39 cases (13.3%), a definite, probable or possible drug event was a dominant or contributing cause of the admission (11.2% ADRs and 2.0% dose-related therapeutic failures). Five of these cases (1.7%) were judged to be due to errors in prescription and a further seven (2.4%) were found to have been avoidable by efforts exceeding the obligatory. There were no statistically significant differences between drug-related and non-drug related admissions in terms of age, sex, number of drugs taken at the admission or duration of hospitalization. ADRs in the geriatric patients are difficult to recognize and may be interpreted as senile loss of function. Sixty-seven percent of the patients took drugs with a sedative action, 68% took drugs with a hypotensive action, 67% took drugs with a potential for confusional states, 15% took drugs with a potential for depression, and 64% took drugs with a potential for constipation. A reduction of the number of drug-related hospital admissions by means of a large-scale intervention would be a difficult task for several reasons: no particular class of drugs caused the drug events, no particular mechanism dominated, no particular group of doctors were responsible for the drug events, and only a part of the drug events were judged to be avoidable.

Aged↗
PubMed1990

The teaching and organisation of clinical pharmacology in European medical schools (W.H.O. Working Group on Clinical Pharmacology).

A World Health Organisation (European Regional Office) working party has been established to review the progress of clinical pharmacology in European countries. As part of this review a questionnaire on the teaching of clinical pharmacology was sent to the Deans of all 350 medical schools in the region. Very few replies were received from U.S.S.R., Greece and Portugal and these countries' returns were not analysed further. The overall compliance rate (excluding these countries) was 82% with a figure of 84% from Western Europe and 74% from Eastern Europe. An average time of 96 h (range 0-320) was devoted to pharmacology teaching in the medical curriculum in Western Europe with 124 (0-240) h in Eastern Europe. In contrast 28 h (0-210) was devoted to clinical pharmacology teaching in Western Europe and 27 h (0-90) in Eastern Europe. On average in Western Europe each medical school had 2 individuals trained in clinical pharmacology with 1.3 posts in the subject and the figures for Eastern Europe were 2.3 and 1.1 respectively. However these figures hide a wide variance in the teaching of clinical pharmacology. Particularly in Western Europe there are a number of medical schools in Italy, Spain and the Federal Republic of Germany (FRG) where clinical pharmacology is not taught and there is a dearth of individuals trained in the subject. Every effort to encourage clinical pharmacology and its teaching should be made, particularly in these countries.

Curriculum↗
PubMed1990

Plasma ratio tryptophan/neutral amino acids in relation to clinical response to paroxetine and clomipramine in patients with major depression.

The pretreatment plasma ratio of tryptophan (Trp) to other large neutral amino acids (LNAA), thought to reflect brain serotonin formation, was determined in 44 inpatients with major depression, who were subsequently treated double-blind on a fixed-dose schedule for 4 weeks with the selective serotonin uptake inhibitor paroxetine (n = 27) or clomipramine (n = 17). The study took place at four clinical centers. Endogenous and non-endogenous depressives were comparable with respect to the ratio Trp/LNAA and clinical improvement and were therefore analyzed together. The clomipramine group showed a significant inverse correlation between ratio Trp/LNAA and improvement, and patients with a ratio Trp/LNAA below the mean showed a trend towards greater improvement than patients with a higher ratio but with comparable serum drug levels. The improvement in the paroxetine group was significantly inversely correlated with the Trp concentration but not with the ratio Trp/LNAA. The findings accord with previous trials of various antidepressant treatments, in which about 25% of the variance in therapeutic response associates with pretreatment plasma amino acid profiles.

Adult↗
PubMed1990

Codeine increases pain thresholds to copper vapor laser stimuli in extensive but not poor metabolizers of sparteine.

The analgesic efficacy and kinetics of a single oral dose of 75 mg codeine was investigated in 12 extensive metabolizers and 12 poor metabolizers of sparteine in a double-blind, placebo-controlled crossover study. The cosegregation of the O-demethylation of codeine to morphine with the sparteine oxidation polymorphism was confirmed. Hence morphine could not be detected in the plasma of any of the poor metabolizers, whereas detectable morphine plasma levels were found in 10 of 12 extensive metabolizers. Pain thresholds to laser stimuli were determined before drug intake and 90, 150, and 210 minutes after drug intake. Codeine significantly increased the pricking pain thresholds in the extensive metabolizers (p less than 0.05), whereas there were no significant changes in the poor metabolizers. No change in pain thresholds occurred with placebo in any of the two phenotypes. In the extensive metabolizers there was a significant positive correlation between the increase in pain threshold and plasma concentration of codeine. The study supports the hypothesis that morphine formation is essential for achievement of analgesia during codeine treatment.

Administration, Oral↗
PubMed1990

Concentration-response relationship in imipramine treatment of diabetic neuropathy symptoms.

A single-blind imipramine dose titration study was conducted in 15 diabetic patients with neuropathy symptoms. The effect of treatment was evaluated by use of visual analog scales. Imipramine doses were individually adjusted until doses yielded plasma concentrations of imipramine plus desipramine that were well above 400 nmol/L or until all neuropathy symptoms had vanished. In all except one patient, there was marked relief of symptoms. In the responding patients (n = 14), much of the effect occurred at plasma levels of imipramine plus desipramine below 100 nmol/L, but a considerable interindividual variation was observed. Concentrations above 400 to 500 nmol/L were required to ensure maximal effect in all patients, and we did not find any indication of a decreased effect at high drug levels. The dose-dependent kinetics of imipramine was confirmed, and dose increments should therefore be carried out in small steps and preferably with monitoring of drug levels.

Adult↗
PubMed1990

Inadequate dosing and pharmacokinetic variability as confounding factors in assessment of efficacy of antidepressants.

The scientific literature on tricyclic antidepressants contains few studies on the dose-effect relationship, and this aspect of the treatment has for many years been given little attention. However, recent reviews point out inadequate dosing as an important factor in "drug resistant depressions." Tricyclic antidepressants have a narrow therapeutic range and standard doses, which are frequently recommended, will not be therapeutic in some patients and toxic in other patients. Use of flexible dose schemes, which has been customary in clinical trials, carry a considerable risk of underdosing because common side effects occur at subtherapeutic doses. Dosing according to therapeutic effect is not feasible in light of the slow and variable rate of response. Much of the difficulties in establishing a dose-effect relationship appears to be related to the considerable pharmacokinetic variability. The major source of this variability is the genetic polymorphism related to the sparteine/debrisoquine oxygenase. For some of the tricyclic antidepressants, a concentration effect relationship has been established, but almost exclusively on the basis of retrospective studies. The dose-response problem is particularly important in clinical trials. Apparent differences or equivalence between a new drug and the control therapy thus may entirely be related to differences in doses of the two drugs. For tricyclic antidepressants, the use of flexible dose schedules and poor control of compliance may often lead to underdosing and a response rate below the real potentials of these drugs. Underdosing combined with a high rate of placebo response will increase the type 2 error risk considerably and may ultimately lead to the introduction of drugs that are less effective than the classical drugs.

Antidepressive Agents, Tricyclic↗
PubMed1990

Nonlinear kinetics of imipramine in low and medium plasma level ranges.

Steady state plasma concentrations of imipramine and desipramine were studied at three to nine different imipramine dose levels in 17 extensive metabolizers of sparteine and at two dose levels in two poor metabolizers of sparteine, all treated for diabetic neuropathy symptoms. The imipramine doses were changed stepwise from doses yielding plasma concentrations of imipramine plus desipramine below 150 nM, up to doses yielding therapeutic drug levels of at least 300-500 nM. The imipramine doses required to achieve therapeutic drug levels was 20 or 25 mg/day in the two poor metabolizers and 50-350 mg/day in the extensive metabolizers. In the extensive metabolizers, the concentration/dose ratio increased for imipramine and desipramine with increasing dose. Dose adjustments based on a simple linear prediction from drug levels at initial dose (50 or 75 mg imipramine/day) thus would result in 0-130% (median, 20%) overestimates, most pronounced in patients with initial low steady state levels. The nonlinear kinetics of imipramine thus may be a significant clinical problem in patients treated for diabetic neuropathy symptoms.

Adult↗
PubMed1990

Quinidine kinetics after a single oral dose in relation to the sparteine oxidation polymorphism in man.

The kinetics at a single oral dose (400 mg) of quinidine were studied in four extensive metabolizers (EM) and four poor metabolizers (PM) of sparteine. The clearance of quinidine by 3-hydroxylation was significantly lower in PM than in EM, but the difference was small (25-30%). This finding suggests that 3-hydroxylation, in part, is catalyzed by the same isoenzyme of cytochrome P450, P450db1 which oxidizes sparteine. Otherwise, no significant phenotypic differences in total or metabolic clearance were found and it is concluded that the metabolism of quinidine is largely carried out by P450 isoenzymes different from P450db1. A biexponential decline in the log plasma quinidine concentration vs time curves was observed in all subjects, and the mean elimination half-life was 11-12 h. This is about twice as long as generally reported in the literature.

Adult↗
PubMed1990

A dose-effect study of the in vivo inhibitory effect of quinidine on sparteine oxidation in man.

1. Twelve healthy extensive metabolisers of sparteine were sparteine tested daily for 6 days (19.00 h to 07.00 h). A small but statistically significant rise in sparteine metabolic ratio (MR) was observed. 2. Following 100 mg quinidine sulphate given to four of the subjects at 16.00 h, sparteine tests were carried out 19.00 h to 07.00 h on the same day and then daily for 6 days. Quinidine caused an immediate twenty-fold increase in sparteine-MR which then gradually returned to normal over the following 4-6 days. Quinidine concentrations in plasma were measurable only up to 20 h after the quinidine test dose. 3. At weekly intervals, all 12 subjects received single doses of quinidine sulphate of 5, 10, 20, 40 and 80 mg at 16.00 h, each time followed by a sparteine test 19.00 h to 07.00 h on the same day. A clear dose-effect relationship was found with a significant rise in the sparteine-MR even after 5 mg quinidine. After 80 mg quinidine, 8 of 12 subjects became phenotypically poor metabolisers (MR greater than 20).

Adult↗
PubMed1990

Clomipramine vs desipramine vs placebo in the treatment of diabetic neuropathy symptoms. A double-blind cross-over study.

1. The effect of clomipramine and desipramine on diabetic neuropathy symptoms was examined in a double-blind, randomised, placebo controlled, cross-over study for 2 + 2 + 2 weeks. Drug doses were adjusted according to the sparteine phenotype, i.e. extensive metabolisers were treated with 75 mg clomipramine day-1 and 200 mg desipramine day-1 whereas poor metabolisers were treated with 50 mg day-1 of both drugs. Nineteen patients completed the study. 2. Plasma concentration of clomipramine plus desmethylclomipramine was 70-510 nM in extensive metabolisers, vs 590 and 750 nM in two poor metabolisers. Desipramine levels were 130-910 nM, vs 860 and 880 nM. 3. Both clomipramine and desipramine significantly reduced the symptoms of neuropathy as measured by observer- and self rating in comparison with placebo. Clomipramine tended to be more efficacious than desipramine. Patients with a weak or absent response on clomipramine had lower plasma concentrations (clomipramine plus desmethyl-clomipramine less than 200 nM) than patients with a better response. For desipramine a relationship between plasma concentration and effect was not established. 4. Side effect ratings did not differ for clomipramine and desipramine and on both drugs three patients withdrew due to side effects. 5. Compared with earlier results obtained with imipramine dosed on the basis of plasma level monitoring, clomipramine and desipramine on fixed doses appeared less efficacious whereas the side effect profiles were the same. At least for clomipramine, appropriate dose adjustment on the basis of plasma level monitoring may increase the efficacy.

Adult↗
PubMed1990

Drug related hospital admissions: the role of definitions and intensity of data collection, and the possibility of prevention.

Three hundred and thirty-three consecutive patients in a medical ward were evaluated in a high-intensity monitoring scheme for drug events as a cause of hospitalization. Taking into consideration only 'definite' and 'probable' drug events, we found 36 cases (10.8%) of all admissions to be drug-related hospitalizations (DRH). Of these, 8.1% were adverse drug reactions and 2.7% were therapeutic failures due to ineffective dosage. In 8 cases (2.4%) the drug event could definitely have been avoided, and a further 13 cases (3.9%) were considered to have been potentially avoidable if appropriate measures had been taken by the health service. In 19 cases (53%) the referring physician was unaware of the drug-related problem. Those patients admitted because of a drug event were taking significantly more drugs than other individuals. The avoidable drug events pointed to the primary health care physicians as the appropriate targets for preventive measures in terms of intensified drug education. The study demonstrated that a reliable estimate of the DRH rate requires active data collection by a qualified health service worker in close collaboration with the patient's family doctor in cases of suspected DRH.

Adolescent↗
PubMed1990

Drug related admissions to a cardiology department; frequency and avoidability.

Three hundred and sixty-six consecutive patients admitted to a department of cardiology were evaluated for drug events as a cause of admission. The drug events considered were adverse drug reactions (ADR) and dose-related therapeutic failures (DTF). 'Definite' or 'probable' drug events accounted for 15 admissions (4.1%, 95% confidence limits 2.3-6.7%), of which eleven were ADR and four were DTF. With the inclusion of six 'possible' drug events, the rate of drug-related hospitalizations (DRH) was 5.7%. DRHs were characterized by a preponderance of acute admissions and elderly patients. Hypokalaemia (less than 3.5 mM) was observed in 27 (16%) patients receiving diuretics, and could be related to four cases of arrhythmias (two 'probable' and two 'possible' ADR). The average serum potassium level was similar in diuretic treated patients with or without drugs to counteract hypokalaemia, irrespective of the drugs chosen. Among the 15 'definite'/'probable' DRHs, five were considered to be due to an error in prescription, and a further five cases were judged to have been avoidable had appropriate measures been taken by prescribing physicians. A DRH educational intervention programme should primarily deal with non-compliance or with prescription of diuretics or digoxin, since these problems constitute the majority of cases of DRH. No specific group of doctors could be targeted as responsible for DRH, avoidable or not.

Cardiovascular Agents↗