Review of the physiological effects of amyl, butyl, and isobutyl nitrites

Does amyl nitrite have a role in the management of pre-hospital mass casualty cyanide poisoning?

CONTEXT

Amyl nitrite has been recommended as a cyanide antidote for several decades. Its antidotal properties were initially attributed to induction of methemoglobin and later to a nitric oxide mediated hemodynamic effect. The ease of administration and alleged rapid clinical effect would recommend its wide use in the pre-hospital management of mass casualty cyanide poisoning; yet there are concerns regarding the use of amyl nitrite for this indication.

OBJECTIVE

Review the data on amyl nitrite in cyanide poisoning and evaluate its efficacy and safety in mass casualty cyanide poisoning.

METHODS

A literature search utilizing PubMed, Toxnet, textbooks in toxicology and pharmacology, and the bibliographies of the articles retrieved identified 17 experimental studies and human reports on the use of amyl nitrite in cyanide poisoning, and 40 additional articles on amyl nitrite's properties and adverse effects. One paper was excluded as it was a conference abstract with limited data.

MECHANISMS OF ACTION

The antidotal properties of amyl nitrite were attributed initially to induction of methemoglobinemia and later to nitric oxide mediated vasodilation.

EFFICACY

EXPERIMENTAL STUDIES

Animal studies on the use of amyl nitrite in cyanide poisoning are limited, and their results are inconsistent, which makes their extrapolation to humans questionable.

EFFICACY

HUMAN STUDIES

Clinical reports are limited in number and the part played by amyl nitrite relative to the other treatments administered (e.g. life support, sodium nitrite, and sodium thiosulfate) is unclear.

ADVERSE EFFECTS

Amyl nitrite can be associated with potentially serious adverse reactions such as hypotension, syncope, excessive methemoglobinemia, and hemolysis in G6PD deficient patients. These effects are more pronounced in young children, in the elderly, and in patients with cardiac and pulmonary disorders. Dose regimen. The method of administration of amyl nitrite (breaking pearls into gauze or a handkerchief and applying it intermittently to the victim's nose and mouth for a few minutes) is not easily controlled, might result in under- or over-dosing, can prevent the caregiver from administering life support, and possibly expose him/her to amyl nitrite's adverse effects.

CONCLUSIONS

Administration of amyl nitrite in mass casualty cyanide poisoning can result in unnecessary morbidity and may interfere with the proper management of the incident and the required supportive treatment and rapid evacuation. In the authors' opinion these drawbacks make the use of amyl nitrite in pre-hospital mass casualty cyanide poisoning unwarranted.

Paradoxical ozone associations could be due to methyl nitrite from combustion of methyl ethers or esters in engine fuels

We review studies of the effects of low ambient ozone concentrations on morbidity that found a negative coefficient for ozone concentration. We call this a Paradoxical Ozone Association (POA). All studies were in regions with methyl ether in gasoline. All but one study carefully controlled for the effects of other criterion pollutants, so the phenomenon cannot be attributed to them. One was in southern California in mid-summer when ozone levels are highest. Because ozone is created by sunlight, the most plausible explanation for a POA would be an ambient pollutant that is rapidly destroyed by sunlight, such as methyl nitrite (MN). A previously published model of engine exhaust chemistry suggested methyl ether in the fuel will create MN in the exhaust. MN is known to be highly toxic, and closely related alkyl nitrites are known to induce respiratory sensitivity in humans. Support for the interpretation comes from many studies, including three linking asthma symptoms to methyl tertiary butyl ether (MTBE) and the observation that a POA has not been seen in regions without ether in gasoline. We also note that studies in southern California show a historical trend from more significant to less significant ozone-health associations. The timing of those changes is consistent with the known timing of the introduction of gasoline oxygenated with MTBE in that region.

Alcohol, drugs and sexual function: a review

The use of psychoactive substances is popularly believed to loosen sexual inhibitions and contribute to increased sexual activity. However, the actual direct and indirect effects of alcohol and drugs on sexual function are still not fully understood. This article provides a new critical review of the research on the impact on male and female sexual function of psychoactive drugs including alcohol, nicotine, and illicit drugs. The authors consider the effects of both acute and chronic use and review findings from controlled laboratory studies as well as survey and interview research. Research on the impact of substance use and abuse on human sexual function has some limitations due to small and nongeneralizable samples, lack of controlled research design or comparison groups, reliance on self-reported data, or failure to specify or control for dosage effects, expectancies, social effects, and multiple substance use. The lack of controls on physiological, psychological, environmental and cultural factors that could alter the relationship between substance use and sexual function also make it difficult to draw conclusions about direct causal mechanisms. Despite these limitations, this review suggests that chronic alcohol and drug abuse have clear deleterious affects on sexual functioning for many individuals.

Pitfalls in the toxicological analysis of an isobutyl nitrite-adulterated coffee drink

A forensic investigation was carried out on one poisoning case, where cyanide was first detected in an evidence sample of a canned coffee drink. A more complete study revealed that it had been adulterated with isobutyl nitrite (IBN) and not cyanide. We examined the detectivity of IBN and related compounds by headspace gas chromatography and capillary electrophoresis. IBN decomposes to isobutyl alcohol (iBuOH) and nitrite in aqueous solution, and under higher temperature and more acidic conditions, the rate of this reaction becomes more rapid. IBN was also produced by the esterification of iBuOH with nitrite below pH 5. Cyanide was produced in a coffee solution by the addition of nitrite below pH 6. An IBN-spiked canned coffee drink solution was stored at 4 degrees C and periodically analyzed for IBN, iBuOH, nitrite, nitrate, and cyanide. Since the IBN level decreased rapidly, iBuOH was produced in an almost 90% molar yield. Nitrite production reached a maximum of 40% molar recovery on the first day and then gradually disappeared. The nitrate level reached a plateau of approximately 60% molar recovery. Cyanide was also detected, and its level at the 14th day was approximately 0.26% molar recovery. These findings suggest that, in a coffee drink solution, IBN undergoes hydrolysis to produce iBuOH and nitric acid, which is oxidized to nitrate and also produces cyanide through the nonspecific oxidation of organic compounds under acidic conditions.

Saturday night blue--a case of near fatal poisoning from the abuse of amyl nitrite

A case of severe methaemoglobinaemia caused by the abuse of volatile nitrites is reported. The agents are commonly abused, but this complication is rare. The clinical presentation can make diagnosis difficult; however, the subsequent treatment needs to be rapid to avoid serious morbidity or mortality. This report presents the clinical picture and the background information leading to the detection and treatment of this unusual problem.

Subtle features of the hemodynamic response to amyl nitrite inhalation: new aspects of an old tool

Although amyl nitrite inhalation (ANI) antedates all current short acting vasodilators as a clinically useful pharmacologic stressor, few clinicians are aware of the subtle hemodynamic actions of this agent. This study examined transients in left and right heart hemodynamics after ANI in seven men (ages 44 +/- 7 years) undergoing elective cardiac catheterization. High-fidelity central aortic (AoP), left ventricular (LVP), pulmonary artery (PAP), right ventricular (RVP), and right atrial (RAP) pressures were simultaneously recorded from left and right heart multisensor catheters. As expected, ANI caused an acute fall in Ao pressure (27%; p < 0.01) and reflex tachycardia (p < 0.001). Little change was noted in PAP, RVP, RAP, or LV end-diastolic pressures or the time constant of LV isovolumetric relaxation (tau). LV ejection time decreased 23 +/- 10 ms (p < 0.05) and RV ejection time did not change. Baroreflex sensitivity was similar during pressure fall and recovery (6.4 +/- 4.5 vs. 6.1 +/- 3.6 ms/mmHg), however hysteresis (p < 0.05) was noted. Aortic pressure waveforms also changed following ANI. Changes were determined to be in part a consequence of the attenuation and delay in arterial wave reflections. This study extends the understanding of the complex nature of the hemodynamic response associated with ANI.

Volatile substance abuse

Volatile substance abuse has been reported in the literature over the past 20 years or so, and has apparently increased as countries have become more industrialised. This review attempts to clarify trends in volatile substance abuse, problems associated with this behaviour and possible solutions. Data sources included a Medline Search on volatile substance abuse over the last five years, Commonwealth publications, recent State and Territory inhouse publications, three research monographs from the National Institute on Drug Abuse (NIDA) and an article library from the author's workplace. Some 250 articles and monographs were identified, reviewed and categorised into sections relating to epidemiology (including mortality), physiological effects and responses to the problem. Articles were used for reference where they reflected the most up-to-date information or where they were seen as authoritative statements. While the body of knowledge concerning volatile substance abuse has improved, little progress has been made in finding effective solutions to the problem. The fact that users are typically young and that there is a real risk of sudden death associated with even initial use suggests that continuing research is needed to develop innovative approaches to the problem.

Regional cerebral blood flow changes associated with amyl nitrite inhalation

Regional cerebral blood flow (CBF), mood states and somatic symptoms were measured before and after inhalation of amyl nitrite in 10 physically healthy volunteers with a prior history of using volatile nitrites for recreational purposes. CBF was measured with the same technique, under identical laboratory conditions, in an equal number of normal volunteers. During CBF measurements, blood pressure, pulse rate, respiratory rate and end-tidal levels of carbon dioxide were monitored. The amyl nitrite group and the control group were compared on CBF, rating scale scores and physiological indices via analysis of variance. Amyl nitrite inhalation was associated with significant global increases in CBF, while the control group did not show any change. Pulse rate increase was the only physiological change associated with administration of the drug. Subjects who received the drug reported significant decrease in anger, fatigue and depression and increased palpitation, breathing difficulty, dizziness and headache. Changes in the rating scale scores, physiological indices, and somatic symptoms after amyl nitrite did not correlate with regional CBF change.

Mutagenicity of thionitrites in the Ames test. The biological activity of thiyl free radicals

Thiols, such as glutathione and cysteine, are mutagenic in the Ames test, using Salmonella typhimurium strain TA 100 and rat kidney S-9 preparation [Glatt et al. Science 220, (1983)]. Formation of thiyl free radicals, RS., has been implicated in this effect. We have prepared thionitrite (nitrosylmercaptan) derivatives of glutathione and other thiols. These unstable derivatives decompose by homolysis, yielding RS. radicals. Glutathione thionitrite is mutagenic to strains TA 100 and TA 102, in the absence of activation by mammalian S-9 preparations. We suggest that this mutagenicity is evidence for the role of thiyl free radicals as biological reactive intermediates. Since alkyl nitrites readily convert thiols to thionitrites, our findings have implications for the toxicology of nitrosating drugs, such as amyl nitrite.

Massive hemolysis following inhalation of volatile nitrites

Volatile nitrites are drugs which have become widely used for their mood-altering and aphrodisiac effects. Their use has been associated with methemoglobinemia and mild hemolysis; more significant hemolysis has been noted in a patient with G6PD deficiency. We report here a case of massive hemolysis following inhalation of volatile nitrites in the absence of an apparent intrinsic red cell defect. It is important that health care workers are aware of side effects from these commonly abused substances.

Inactivation of B12 and folate coenzymes by butyl nitrite as observed by NMR: implications on one-carbon transfer mechanism

The effects of butyl nitrite, a frequently used recreational drug, on methyl cobalamin and 5-methyl tetrahydrofolate were investigated by using 1H and 31P NMR spectroscopies. While no effect could be observed in organic solvents, strong interactions of butyl nitrite with the methyl cobalamin and 5-methyl tetrahydrofolate were found to occur in water. Butyl nitrite decomposes in water generating H+ and NO-2. The former protonates to give the "base-off" configuration of methyl cobalamin while the Co-CH3 bond is cleaved. Similarly, the methyl group at the 5N position and the pyrazine ring of 5-methyl tetrahydrofolate were found to be affected by butyl nitrite. The overall interaction of butyl nitrite with both coenzymes shows displacement of the methyl group and derivatization or destruction of the coenzymes that may lead to deficiencies of both B-12 and/or folates.

Volatile nitrites. Use and adverse effects related to the current epidemic of the acquired immune deficiency syndrome

Early reports of the acquired immune deficiency syndrome (AIDS) in homosexual men suggested that the cause might be related to homosexual life-style practices, including use of recreational drugs. Inhalation of volatile nitrites is a possible contributing factor in AIDS because their pharmacologic properties lead to toxicity. Metabolism of N-nitroso compounds produces mutagens, teratogens, and potent carcinogens in 39 different animal species, and volatile nitrites have deleterious effects on human lymphocytes in vitro and in vivo. In relation to the current AIDS epidemic, the timing of production and sales of volatile nitrites for recreational use is the only new life-style factor that might answer the question "why AIDS now?" Prevalence of nitrite use among male homosexuals is very high, and almost every reported case of Kaposi's sarcoma during the past three years includes a history of prior nitrite use. The age of the group of patients in whom Kaposi's sarcoma and AIDS are developing is consistent with a cohort initially exposed seven to 10 years ago. Cessation of nitrite use could reduce the epidemic.

Subchronic inhalation toxicity of isobutyl nitrite in BALB/c mice. II. Immunotoxicity studies

Initial epidemiologic studies of acquired immunodeficiency syndrome (AIDS) occurring in homosexual men identified the use of the inhalants amyl, butyl, and isobutyl nitrite as possible risk factors contributing to the disease. Because of the lack of immunotoxicological data on these chemicals, we studied the effects of subchronic exposure to isobutyl nitrite (IBN) on the immune system. BALB/c mice were exposed to either 50 or 300 ppm IBN for 6.5 h/d, 5 d/wk for up to 18 wk. After 7, 13, or 18 wk of exposure, mice were killed and the following assays were performed. Antibody producing cells were enumerated by a slide plaque assay on animals immunized with sheep red blood cells while still in exposure chambers. The lymphocyte proliferative response to mitogens (phytohemagglutinin, concanavalin A, pokeweed mitogen, and lipopolysaccharide) was tested using several concentrations of each mitogen. Additional mice were immunized with Freund's complete adjuvant 21 d prior to death and were tested for delayed hypersensitivity response to purified protein derivative by a radiometric skin test. Finally, the relative numbers of T cells and T-cell subsets among splenic lymphocytes from exposed and control animals were determined. At the time periods tested there were no discernable immunotoxic effects observed in the exposed animals in any of the assays performed. These results indicate that IBN, at the dosages tested, had no discernable detrimental effect on the immune system of mice.

Risk factor analysis among men referred for possible acquired immune deficiency syndrome

Responses to a lifestyle questionnaire among 13 patients with Kaposi's sarcoma and 18 with an opportunistic infection were compared with those of 29 symptom-free referred individuals. Odds ratios (OR) with 95% confidence limits were calculated as an estimate of risk. Significantly elevated odds ratios (P less than 0.05) were found for cigarette smoking (OR = 3.4), marijuana use (OR = 3.7), nitrite use (OR = 5.5), frequenting bathhouses (OR = 7.6), prior syphilis (OR = 3.4), and fist-rectal sexual practices (OR = 3.5). A response gradient for the risk estimates was found for marijuana use (OR = 2.7 for occasional, OR = 4.3 for frequent use); nitrites (OR = 4.0 for occasional; OR = 6.3 for frequent use); and prior syphilis (OR = 2.9 for one to two previous infections and 9.0 for three or more). We believe the evidence is now sufficient to recommend preventive practices which may reduce the male homosexual's risk for developing acquired immune deficiency syndrome, Kaposi's sarcoma, and/or opportunistic infections. These include cessation of cigarette smoking, marijuana use, and nitrite inhalation; reduction in number of anonymous sexual partners to decrease risk of sexually transmitted diseases; and avoidance of fisting.

Subchronic inhalation toxicity of isobutyl nitrite in BALB/c mice. I. Systemic toxicity

The effects of subchronic inhalation exposure to isobutyl nitrite (IBN) on body weight, selected organ weights, hematology, and gross pathology and histopathology of BALB/c mice were evaluated. Mice of both sexes were exposed at 0, 20, 50, or 300 ppm IBN for 6.5 h/d, 5 d/wk for up to 18 wk. Most changes in measured indices occurred in mice exposed at 300 ppm IBN and included decreased thymus weight (females); decreased liver weight (males); decreased white blood cell counts (males); mild focal hyperplasia and vacuolization of the epithelium lining bronchi and bronchioles of the lungs (males and females). Organ weight and hematologic changes, however, were not accompanied by any observed histologic changes. In addition, elevated methemoglobin concentrations were detected in mice of both sexes exposed at 50 and 300 ppm IBN. Body weights were not adversely affected by exposure. These data suggest that mild tissue injury, restricted to the lung, and methemoglobinemia are the major toxic effects observed following exposures of mice to IBN at concentrations up to 300 ppm for 18 wk. No treatment-related effects were noted in mice exposed at 20 or 50 ppm IBN, except for slight elevations in methemoglobin concentrations in mice exposed at 50 ppm.

Recreational drugs: relationship to AIDS

Current data suggest that a transmissible agent causes AIDS, but undefined cofactors may also play a role. This paper reviews published data on the relationship between recreational drugs and immune alterations, with particular emphasis on nitrite inhalant (NI) use by homosexual men. In our original cohort of 15 homosexual men, helper:suppressor (H:S) T-cell ratios are stable, but persistently lower in the NI users. A recent analysis of 245 homosexual men shows that NI use is associated with low H:S ratios in homosexual men in Washington, D.C., but not in New York. Although NI use could increase the risk of AIDS by direct or indirect effects, it could also be a surrogate for a lifestyle practice that predisposes homosexual men to the putative AIDS agent. The current evidence concerning use of NI and the risk of AIDS is inconclusive, as is true for two other recreational drugs, heroin and cocaine. Future studies may not be able to dissect the complex interrelationships of drug use and other variables until precise laboratory tests are available for defining exposure to the putative AIDS agent and suspect cofactors.

Toxicity, immunosuppressive effects and carcinogenic potential of volatile nitrites: possible relationship to Kaposi's sarcoma

Volatile nitrite in the form of amyl nitrite was used for 100 years for the treatment of angina pectoris. In spite of recognized toxicity, its use in this form was considered safe. During the 1960s prescriptions were not required for purchase of amyl nitrite (called poppers) and its use for recreational purposes became popular. With reinstatement of the prescription requirement in 1969, non-medicinal, street-variety volatile nitrites were made commercially available in the form of mixtures of impure butyl and isobutyl nitrite; some of these preparations also included amyl nitrite. These products have been found to be profoundly immunosuppressive for human lymphocytes in vitro, and their by-products when metabolized into N-nitroso compounds have been known to be highly carcinogenic in many animal species. Recreational use of inhaled volatile nitrites is prevalent among male homosexuals and the compounds have been suspected as possible cofactors in Kaposi's sarcoma associated with the Acquired Immune Deficiency Syndrome (AIDS). This association could be explained by nitrite-induced vasodilation of rectal mucosal vessels providing a port of entry for a transmissible agent, by direct immunosuppression of the host allowing expression of a potentially oncogenic virus by co-carcinogenic effects of by-products by themselves or in conjunction with other putative cofactors such as cytomegalovirus. Nitrites should continue to be considered as a possible cofactor in the etiology of Kaposi's Sarcoma among male homosexuals and possibly those with other manifestations of AIDS.

Depression of murine natural killer cell cytotoxicity by isobutyl nitrite

We have investigated the effect of isobutyl nitrite on murine NK-cell antitumor-directed cytotoxicity. This agent has been suggested as one of the factors underlying immunodeficiency syndrome (AIDS) in man. We demonstrated that two injections, each of 0.25 ml isobutyl nitrite, resulted in significant depression of endogenous splenic and peripheral blood natural killer (NK) cell cytotoxicity against T-cell lymphoma, YAC-1. In addition to endogenous NK cells, activity of pyrimidinol-activated NK cells was also substantially depressed by this agent. The latter observation is of the utmost importance, since it suggests that the attempt to augment NK-cell activity (to promote resistance to infections and malignancies) could fail in patients with AIDS who are isobutyl nitrite users. Isobutyl nitrite was NK-cell-suppressive not only after in vivo administration but, most importantly, also after inhalation. This indicates that isobutyl nitrite, via its NK-cell suppressive effect, could contribute to immunodeficiency in AIDS. Studies on the mechanism of NK-cell depression by isobutyl nitrite demonstrated that the NK-cell tumor-binding properties as well as NK-cell cytotoxic potential were substantially depressed. Mixing experiments failed to reveal any regulation by suppressor cell activities. The results of these studies clearly indicate that isobutyl nitrite is an immunosuppressive agent and that its use should be avoided.

Acquired immune deficiency syndrome and the management of associated opportunistic infections

Since the spring of 1981, more than 2300 cases of acquired immune deficiency syndrome (AIDS) have been reported from 41 states to the Centers for Disease Control. Cases also have been reported from 20 foreign countries, and reports are increasing at an alarming rate. More than 900 people (approximately 40 percent) have died of this disease. AIDS is characterized by skin test anergy to recall antigens, decreased T-helper subset, and inverted helper T-cell:suppressor T-cell ratios in the peripheral blood. Overt AIDS may be preceded by a prodrome that may last for many months and consists of fever, weight loss, and lymphadenopathy. The immune defect in AIDS permits the development of opportunistic infections caused by a number of organisms, including Pneumocystis carinii, Mycobacterium avium-intracellulare, Toxoplasma gondii, and various fungi. Certain malignancies also are associated with AIDS, in particular, Kaposi's sarcoma. Although the etiology of AIDS is unknown, the causative agent appears to be infectious. Lifestyle factors such as drug use and certain sexual activities may play a role. Currently, epidemiologists and others investigating the syndrome believe that AIDS can spread through sexual contact, blood products, or both. AIDS patients include homosexual males, users of intravenous drugs, immigrants from Haiti, hemophiliacs, female partners of males with AIDS, infants born to mothers who have AIDS, and persons who have received blood products from AIDS patients. Thus far, questions about AIDS outnumber the answers. Intensive research is being conducted to develop a rational approach to the treatment of AIDS and a better understanding of the relationship between the immune defense system and cancer.

Cellular immunotoxicity of amyl nitrite

Functional deficits in lymphocyte interaction following occasional or chronic exposure to inhaled nitrites may be a potential contributing but not the etiologic factor in the acquired immunodeficiency syndrome (AIDS). We evaluated the effect of amyl nitrite vapors on mononuclear cell function and demonstrated functional deficits and structural alterations in these cells. In this closed, in vitro system, exposure of cells to amyl nitrite for up to 30 minutes did not effect cell viability. The functional deficits demonstrated were: inhibition of lymphocyte erythrocyte (E) rosette formation, a suppression of lymphocyte mitogen (phytohemagglutinin) and antigen (cytomegalovirus) transformation, a block in the S, G2 and M phases of cell cycling and diminished cell cytotoxicity to CMV infected cells. These effects on cellular function were demonstrated following 5, 10, and 15 minutes of amyl nitrite vapor exposure; some effect on all cellular functions was demonstrated at 5 minutes. The structural alterations seen on scanning and transmission electron micrographs were: reduction of filapodia, smoothing of the cell profile, cytoplasmic protrusions with pseudopod-like extensions, an increase in rough endoplasmic reticulum with swollen cisternae, alterations in size and distribution of golgi components and exocytotic vesicles in the outer membrane of the nuclear envelope. These vesicles and increased membrane proliferation suggests an effect on the membrane synthesis mechanism in these cells. These effects may be a potential factor in the alterations of phenotypic markers on T lymphocyte populations, as well as, a potential contributing factor in the functional deficit of mononuclear cells in patients with AIDS.

Amyl nitrite may alter T lymphocytes in homosexual men

To evaluate the recent outbreak of Kaposi's sarcoma (KS) and opportunistic infections in homosexual men, clinical, virological, and immunological data on two homosexual men with KS and on fifteen healthy homosexual volunteers were collected. Both KS patients had regularly used amyl or butyl nitrite (AN); they had low helper/suppressor (H/S) T-lymphocyte ratios before chemotherapy and high titres of antibody against cytomegalovirus (CMV). Eight of the fifteen volunteers were regular AN users; seven of the eight had low H/S ratios due to larger than normal numbers of OKT8-positive suppressor cells and smaller numbers of OKT4-positive helper cells. In all eight AN users the fluorescence profile obtained with monoclonal antibody 9.6 (which detects the sheep E-rosette receptor) was bimodal, indicating a subpopulation of T cells with increased receptor density. A similar pattern was observed when OKT8, the antibody which detects cytotoxic suppressor cells, was used. Two of the seven men who did not use AN had abnormal fluorescence with reagent 9.6, and one of these also had a low H/S ratio. CMV-antibody titres were persistently high in fourteen of the fifteen healthy men, but the titres were not related to AN use of T-cell abnormalities. The data suggest that nitrites may be immunosuppressive in the setting of repeated viral antigenic stimulation and may contribute to the high frequency of DS and opportunistic infections in homosexual men.