Enzyme induction in man caused by smoking

Menstrual disturbances in thyrotoxicosis

OBJECTIVES

In thyroid textbooks it is stated that hyperthyroidism in women may be associated in almost 50% of the cases with hypomenorrhoea, oligomenorrhoea or amenorrhoea and perhaps with reduced fertility. Our experience at a busy thyroid clinic has given a picture which differs from that described in the literature. Most of our female thyrotoxic patients had normal menstruation. This study was performed to define the menstrual abnormalities in hyperthyroidism.

DESIGN AND PATIENTS

We investigated the menstrual history, starting 6 months before the discovery of the disease, the smoking habits and the body mass index (BMI), in 214 female, premenopausal thyrotoxic patients and a similar number of normal controls matched for age and weight.

MEASUREMENTS

TT4 and TT3 were measured by radioimmunoassay, while BMI was calculated from the ratio of body weight in kg to height in m2.

RESULTS

Of the 214 patients, 168 (78.5%) had regular menstrual cycles and 46 (21.5%) irregular cycles. No difference in BMI was found between the patients with or without menstrual abnormalities. Out of the 46 patients with irregular periods, 23 (50%) were smokers, while only 32 out of the 168 patients (19%) with normal periods were smokers (P < 0.001). TT4 levels were higher as a group in patients with menstrual disturbances (mean +/- SD 267.7 +/- 66.9 nmol/l) than in those with normal periods (240.6 +/- 47.6 nmol/l) (P < 0.05). The 23 smokers with irregular periods had higher TT4 levels (280.5 +/- 51.8 nmol/l) than the remaining non-smokers from the same group (241.9 +/- 43.7 nmol/l) (P < 0.01). No such differences were found for TT3 levels. Out of 214 normal controls, matched for age and weight, 196 (91.6%) had normal menstruation and 18 (8.4%) irregular cycles. The latter group included mainly women with oligomenorrhoea. Out of 18 normal controls with irregular periods, 6 (33.3%) were smokers, while 57 (29.1%) out of 196 with normal periods were smokers.

CONCLUSIONS

These data demonstrate that hyperthyroidism in women is less frequently associated with menstrual abnormalities than was previously believed. Furthermore, no patient presented with amenorrhoea. Smoking and TT4 levels are strongly associated with the occurrence of menstrual disturbances in thyrotoxicosis.

Age, environmental factors and drug metabolism

Both ageing and the environment have a significant impact on xenobiotic metabolism. Furthermore, there is some evidence from in vivo studies that the elderly respond to environmental changes to a lesser degree than younger individuals. This article reviews the available evidence and concentrates on possible underlying mechanisms.

Lack of effect of cimetidine on cigarette smoking

The efficacy of cimetidine as a treatment that could reduce smoking in heavily dependent smokers has been determined. In a randomised, double-blind, double-crossover experiment, 43 heavy smokers were divided into two groups, one receiving cimetidine 400 mg orally three times a day, and the other receiving placebo for two weeks followed by the alternative treatment (placebo or cimetidine). No significant difference in the mean alveolar carbon monoxide, nicotine or cotinine levels was found between the two treatment groups compared to baseline. Since the alveolar carbon monoxide level reflects the intensity of smoking behaviour, the results suggest that no change in smoking behaviour occurred in the subjects. Contrary to our previous findings that cimetidine decreased the total body clearance of nicotine by 30% in a population of non-smokers, in the heavily dependent smokers, cimetidine did not appear to alter nicotine elimination. One possible explanation for the discrepancy is that tobacco smoking is known to induce nicotine metabolism and the induction might have offset any effect of cimetidine on nicotine elimination. Cimetidine does not appear to be a useful treatment leading to a reduction or cessation of cigarette smoking.

Sensitivity and tolerance to nicotine in smokers and nonsmokers

We studied the responses of smokers and lifelong non-smokers to transdermal nicotine patches over 24 h in three groups of subjects: non-smokers on a 15 mg patch (n = 8), non-smokers on a 30 mg patch (n = 8) and smokers on a 30 mg patch (n = 8). Unexpectedly, the non-smokers appeared to absorb nicotine more rapidly. The increase in blood nicotine concentrations of non-smokers over the first 2 h of patch use was double that of the smokers, with mean increases of 4.5 (SD = 3.7), 10.9 (SD = 4.2) and 4.1 (SD = 2.7) ng/ml in the three groups, respectively (P less than 0.005). The smokers had no pleasant or unpleasant effects from the 30 mg patch (X Cmax 13.9 ng/ml, SD = 4.9; Tmax 8.75 h) but all eight non-smokers experienced mild nausea and lightheadedness (P less than 0.01) within the first hour, and seven dropped out (P less than 0.01) at 3-8 h due mainly to severe nausea, vomiting or headache (X Cmax 18.4 ng/ml, SD = 4.9; Tmax 5.25 h). Only one non-smoker dropped out on the 15 mg patch, but five had transient nausea in the first hour (X Cmax 7.9 ng/ml, SD = 3.0; Tmax 8.0). Our study provides evidence of chronic pharmacodynamic nicotine tolerance in smokers, but does not address whether this is acquired or innate. The higher rate of transdermal nicotine absorption in non-smokers is unexplained and requires replication.

Elimination of cotinine from body fluids: disposition in smokers and nonsmokers

We have evaluated differences in the elimination of cotinine, a major nicotine metabolite, in smokers who quit smoking and never-smokers who were exposed to environmental tobacco smoke (ETS) under controlled conditions. The mean biological half-life of cotinine in urine, collected from the nine smokers was 16.5 +/- 1.2 h, in never-smokers exposed to ETS, 27.3 +/- 1.9 h. Differences in the mode of uptake and absorption of nicotine and possible differences in nicotine metabolism may play roles in the clearance rate differences between smokers and nonsmokers.

Disopyramide pharmacokinetics and metabolism: effect of inducers

1. The disposition of orally administered disopyramide was studied in a population of smokers (n = 6) and non-smokers (n = 8) before and during phenobarbitone treatment (100 mg daily for 21 days; Cp 21st day = 13.9 +/- 2.0 micrograms ml-1). The comparative inducibility of these populations by phenobarbitone was assessed as was the inductive effect of cigarette smoking, per se. Furthermore, the determinants of the intensity of the inductive effect were examined, as well as the effect of the barbiturate on the binding of disopyramide to alpha 1-acid glycoprotein (AGP). 2. Smokers and non-smokers exhibited similar half-lives (6.48 +/- 1.49 vs 6.66 +/- 1.02 h), apparent total body clearances (0.100 +/- 0.020 vs 0.117 +/- 0.034 l h-1 kg-1), mean renal clearances (0.043 +/- 0.0093 vs 0.057 +/- 0.013 l h-1 kg-1) and apparent intrinsic metabolic clearances (0.057 +/- 0.015 vs 0.060 +/- 0.024 l h-1 kg-1) before phenobarbitone treatment. 3. Both populations responded comparably to barbiturate exposure in that apparent intrinsic metabolic clearance more than doubled. Interestingly, the magnitude of this increase was highly dependent on the observed baseline apparent intrinsic metabolic clearance, (r' = 0.81; P less than 0.001). 4. Phenobarbitone treatment of non-smokers resulted in an increase in the AUC of the active metabolite N-despropyl disopyramide (MND), but not significantly (3.8 +/- 1.6 vs 4.1 +/- 2.3 micrograms ml-1 h). Similar results were observed in smokers (3.5 +/- 1.4 vs 3.9 +/- 2.0 micrograms ml-1 h, respectively). 5. The percent of administered dose recovered in urine as disopyramide in non-smokers was significantly decreased upon phenobarbitone treatment (43 +/- 6% vs 25 +/- 5%), whereas the percent of dose recovered as MND increased significantly in this group (25 +/- 6% vs 31 +/- 5%). The population of smokers responded similarly. 6. At doses typically used to achieve hepatic microsomal enzyme induction in man, phenobarbitone treatment caused no significant change or trend towards a change in serum AGP concentrations as measured using the radial immunodiffusion method in nonsmokers (67.4 +/- 19.9 mg dl-1 vs 68.0 +/- 40.7 mg dl-1) or smokers (64.5 +/- 15.7 vs 67.9 +/- 14.9). Similarly, when AGP concentration was estimated in serum from non-smokers using a nephelometric method no effect attributable to phenobarbitone was observed (47.9 +/- 1.3 vs 47.9 +/- 16.8 mg dl-1). Consistent with this observation, disopyramide free fraction was not affected by barbiturate treatment.

Clinical pharmacokinetics of nicotine

Nicotine intake is considered to be a major factor in sustaining tobacco addiction. For this reason, nicotine gum has recently been introduced as an adjuvant to smoking cessation. The introduction of nicotine as a 'therapeutic' entity necessitates a careful examination of its clinical pharmacokinetics. Insufficient data exist to quantitatively assess the absorption of nicotine after oral administration. Based upon physicochemical and pharmacokinetic principles, the oral bioavailability of nicotine would be expected to be less than 20%. The limited data available in the literature appear to support this conclusion. Absorption from the oral mucosa is the principal site of nicotine absorption in subjects who chew tobacco or nicotine gum. Absorption by this route is highly pH dependent. Nicotine is also readily absorbed from the nasal mucosa, and after topical administration. Nicotine distributes extensively into body tissues with a volume of distribution ranging from 1.0 to 3.0 L/kg. Nicotine has been shown to transfer across the placenta and into breast milk in humans. Plasma protein binding is negligible, ranging from 4.9 to 20%. The predominant route of nicotine elimination is hepatic metabolism. Although a number of metabolites of nicotine have been identified, it is unclear whether any of these compounds contribute to the pharmacological effect of nicotine. Nicotine is also excreted unchanged in urine in a pH-dependent fashion. With urinary pH less than 5, an average 23% of the nicotine dose is excreted unchanged. When urinary pH is maintained above 7.0, unchanged nicotine urinary excretion drops to 2%. After intravenous administration, nicotine exhibits biexponential decline in plasma. Total plasma clearance ranges from 0.92 to 2.43 L/min. During urinary acidification, renal clearance averages 0.20 L/min. Non-renal blood clearance averages 1.2 L/min, indicating that nicotine elimination is dependent on hepatic blood flow. The literature is devoid of information regarding the effect of disease on the pharmacokinetics of nicotine. Based upon the drug's pharmacokinetics in healthy smokers, it would be anticipated that disease states which alter hepatic blood flow may have the greatest impact on nicotine pharmacokinetics. In addition, drugs which alter hepatic blood flow may cause significant alterations in the systemic clearance of nicotine. Dependence on smoking appears to be related, at least in part, to the achievement of a rapid rise in plasma nicotine concentrations. If this assessment is correct, the most desirable adjuvant for smoking cessation would be one that closely mimics this pattern of plasma nicotine concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of chronic exposure to carbon disulfide on biotransformation of phenazone in rabbits

A significant but reversible inhibition of phenazone elimination was observed in rabbits chronically exposed to CS2. Lack of significant difference of phenazone pharmacokinetics in exposed rabbits 24 h after the last exposure compared with the control group, indicates that alteration of phenazone elimination after chronic exposure to CS2 is reversible. The results obtained with phenazone as a model substance suggest that, during chronic exposure to CS2, elimination of other drugs metabolized by the pathway similar to phenazone may also be altered. This should be taken into account in selecting their dosage.

No effect of smoking on sulfamethazine acetylation

Seven healthy subjects who smoked at least one pack of cigarettes/d were acetylator-phenotyped with sulfamethazine (SMZ) while they were actively smoking, and again at least one month after they had completely stopped. There were no significant differences of the acetylation profiles in the smoking vs. nonsmoking state, as measured by %ASMZ in serum six hours post-SMZ dosing or by %ASMZ in urine five to six hours post-SMZ dosing. We conclude that smoking does not influence SMZ acetylation and probably does not affect drug acetylation in general.

Human cytochromes P-450

Studies in vivo have provided evidence for a multiplicity of cytochromes P-450 in man, some of which are under independent monogenic control. Although the activity of cytochromes P-450 in man are generally lower than those of rat, this is by no means always the case. There are several important exceptions including the N-hydroxylation of 2-acetamidofluorene. Studies in vitro by a number of different techniques have confirmed the evidence from studies in vivo that there are multiple forms of human cytochrome P-450. In addition to differences in Vmax, the different forms of cytochrome P-450 may also exhibit marked differences in their apparent Km values. The implications that this may have for pharmacokinetics and toxicology are discussed. The polymorphism in the 4-hydroxylation of debrisoquine observed in vivo has been shown to be due to a defect in a specific form of cytochrome P-450 which appears to be under monogenic regulation. Cross-inhibition studies have enabled the specificity of this isozyme to be characterized. Such studies have also enabled the contribution of this isozyme of cytochrome P-450 to the oxidation of other substrates to be determined. Compounds investigated include bufuralol and phenytoin. Evidence from studies both in vivo and in vitro suggest that selective induction of different forms of cytochrome P-450 can occur in man. However, the number of different classes of inducer in man is not yet known. Human cytochromes P-450 have been purified to near homogeneity in several laboratories. Different forms of cytochrome P-450 purified from the same liver sample vary in molecular weight, chromatographic characteristics and substrate specificities.

Effects of urinary pH on the behavioral responses of squirrel monkeys to nicotine

The present study evaluated the behavioral effects of nicotine under conditions that manipulated urinary pH. The effects of nicotine were examined on the responding of squirrel monkeys under a multiple fixed-interval, fixed-ratio schedule of stimulus-shock termination when nicotine was administered alone or together with the gastric administration of an acidifier (ammonium chloride) or an alkalinizer (sodium bicarbonate). Responding under the FI schedule was increased markedly across a range of doses of nicotine (0.02-0.20 mg/kg). Responding under the FR was increased to a lesser extent by the lower doses of nicotine (0.02-0.05 mg/kg) and was decreased by doses of nicotine that increased responding under the FI (0.10-0.20 mg/kg). Generally, administration of the acidifier attenuated the effects of nicotine while administration of the alkalinizer potentiated those effects. These findings support the argument that changes in cigarette smoking under conditions that alter urinary pH involve nicotine per se. In addition, a new interpretation of the relationship between urinary pH and cigarette smoking is offered.

Menopausal age in various ethnic groups in Israel

The effects of various parameters on age at menopause have been investigated in five ethnic groups in Israel comprising East European, West European, North African, Israeli and other Middle Eastern (Mediterranean) women, respectively. The data were acquired by means of anonymous questionnaires and were programmed for 1770 women. Correlation coefficients between various variables and age at menopause revealed three variables which have a straight correlation, vis. obesity index, number of children, and years of amenorrhoea (during the reproductive years). The years-of-smoking variable has an inverse correlation with age at menopause. East Europeans have the highest age at menarche. Two-way analysis of variance has shown that the obesity index, years of amenorrhoea, number of children and years-of-smoking parameters are individually more important than ethnic origin. The finding that the age at menopause is highest in the North African group is explained by the higher incidence in this group of high parity, a greater number of amenorrhoea, obesity, and low cigarette consumption. Since many habits (such as smoking, diet, use of contraceptive pills, multiple partners and marital obligations) are subject to frequent change in the modern world, it is of the utmost importance to repeat such a study every few years.

An evaluation of the effects of smoking on codeine pharmacokinetics and bioavailability in normal human volunteers

Cigarette smoking has been shown to increase the clearance of several drugs, including pentazocine, theophylline, and phenacetin. This effect presumably is mediated through enzyme induction, resulting from inhaled polycyclic aromatic hydrocarbons. Because the O-demethylation pathway for codeine is similar to that of other drugs known to be influenced by cigarette smoking, a study was conducted to compare the pharmacokinetics and metabolism of codeine in smokers and nonsmokers. Twelve volunteers with no history of cigarette smoking and ten volunteers who smoke cigarettes were studied; an open, two-treatment, simultaneous parallel and crossover study design was used. Each volunteer received a single dose of codeine sulfate 60 mg po and codeine phosphate 60 mg im, in random treatment order, at one-week intervals. Serial blood samples were collected up to 12 hours after dosing, and plasma codeine and morphine concentrations were measured by radioimmunoassay. There was no significant difference between smokers and nonsmokers in either codeine or morphine areas under the plasma concentration-time curves (AUCs), with either route of administration. The relative codeine bioavailability in these groups was 54.8 +/- 4.9 percent and 50.2 +/- 2.1 percent (mean +/- SE), respectively. Smoking was associated with greater variability in plasma concentrations. Interestingly, greater morphine:codeine AUC ratios were observed in both groups after oral than after intramuscular administration. Cigarette smoking should have no clinically important influence on codeine absorption or disposition.

Physiological predisposition toward becoming a cigarette smoker: experimental evidence for a sex difference

In two experiments, nonsmoking females whose urine was acidified were more willing after smoking one cigarette to volunteer to smoke additional cigarettes than were females whose urine was made alkaline. Males did not exhibit this effect. The results indicate that physiological factors that influence nicotine intake during the early smoking experiences of nonsmokers help determine who becomes a cigarette smoker, at least for females. These results may help us interpret recent increases in smoking among teenage females.

Coffee consumption, cigarette smoking and reporting of drowsiness in anxious patients treated with benzodiazepines or placebo

Data obtained from anxious outpatients treated with either chlordiazepoxide or diazepam (n = 533) or placebo (n = 285) were used to explore the impact of coffee/tea and cigarette consumption upon the frequency of reporting of drowsiness after 2 weeks of treatment. Strong evidence was provided that both cigarette smoking and coffee drinking affect the frequency with which drowsiness is reported by patients receiving the two benzodiazepines. However, not only the magnitude but also the direction of the impact of coffee consumption upon drowsiness depends upon the level of cigarette smoking and vice versa. For patients smoking less than or equal to 1 pack of cigarettes/day, drowsiness is reported less frequently by heavy coffee users while for patients smoking greater than 1 pack of cigarettes/day, drowsiness is reported more frequently by heavy coffee users. Similarly, for patients drinking less than or equal to 2 cups of coffee/day, drowsiness occurs less frequently among heavier smokers while for patients drinking greater than 2 cups of coffee/day, drowsiness occurs more frequently among heavier smokers. These results are consistent with reports that particular substances contained in coffee and tea and in cigarette smoke stimulate the synthesis of hepatic enzymes which metabolize both the benzodiazepines here studied and the substances which have stimulated enzyme synthesis.

The relationships between clinical response, psychophysiological variables and plasma levels of amitriptyline and diazepam in neurotic outpatients

In a 4 week study of the response of neurotic outpatients to treatment with amitriptyline, diazepam, amitriptyline and diazepam, or placebo clinical and psychophysiological variables and plasma levels of the drug were assessed. Clinical improvements were substantial in all treatment groups but clear relationships between clinical change, psychophysiological change and plasma levels of the drugs were not established. There was no relationship between plasma levels of the drugs and cigarette smoking. It is concluded that neither plasma levels of amitriptyline and diazepam nor change in skin conductance responsivity offer a useful guide to clinical response to drug treatment.

Influence of cigarette smoking on drug metabolism in man

The pervasiveness of tobacco use in our society and the frequency of altered disposition of many common therapeutic and recreational drugs in smokers makes it apparent that the smoking habit should be considered as one of the primary sources of drug interactions in man. Each scientific report dealing with drug disposition should list the smoking status of the subjects studied as smoking should be included as a basic characteristic of each subject along with age, race, body weight, and presence and type of disease. Most of the experimental work in human and animal systems indicates that the dominant effect of smoking is enhanced disposition caused by induction of hepatic microsomal enzymes. The primary causal agents are probably the polynuclear aromatic hydrocarbons which are potent and persistent in tissues. There are numerous examples of both an increased metabolism rate and absence of an effect of smoking on drug disposition in man. This selectivity is consistent with the known inductive effects of P-448 stimulators in animal systems. Studies with theophylline have demonstrated that both tobacco and marijuana markedly alter its clearance in man. However, smoking is only one of numerous factors which can perturb hepatic biotransformation as patient surveillance studies show that age and cardiac and liver disease may be of greater importance in actual patients undergoing therapy.

Relation between smoking and age of natural menopause. Report from the Boston Collaborative Drug Surveillance Program, Boston University Medical Center

The relation of cigarette smoking to natural menopause has been evaluated in two independent sets of data. In both, at each age from 44 to 53 years, more current smokers were post-menopausal compared to "never" smokers. In the first set of data the age-standardised proportions of women who were postmenopausal were 35, 36, 43, and 49%, respectively, for never smokers, ex-smokers, and current smokers of 1/2 and greater than or equal to 1 pack per day. The corresponding proportions for the second set were 53, 59, 60 and 65%.

The influence of smoking on the intersubject variation in pentazocine elimination

The cumulative urinary excretion over 24 h of pentazocine, under conditions of acidic urinary pH, has been measured in smokers and non-smokers using both male and female subjects (seventy subjects in total). A restricted urban population was studied. An overall three-fold inter-subject variation in elimination was observed. The cumulative urinary excretion of pentazocine was normally distributed in both smokers and non-smokers. Smokers metabolize 40% more pentazocine than non-smokers. It is concluded that induction is principally responsible for the observed subject variability.

Tolerance development to the arousal effects of nicotine

To determine if repeated daily doses of nicotine induces tolerance to both its EEG and behavioral activating effects, rats implanted with sets of bipolar cortical elecrodes and carotid cannulae received intracarotid injections of either (1) 6 daily doses of nicotine (as tartrate, 30 mug/kg) (Group 1) or (2) 3 daily doses of saline followed by 4 days of nicotine (Group 2). From an exercise-induced resting state, nicotine produced immediate EEG and behavioral arousal, both of which disappeared in Group 1 by Day 6. Saline administered to Group 2 rats produced little or no response but subsequent nicotine resulted in responses similar to those produced by Group 1 animals. It is concluded that tolerance development to nicotine activation is reflected not only in behavior, but also in the EEG.