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57-451: Phenylpropanolamine ( PPA ), sold under many brand names, is a sympathomimetic agent which is used as a decongestant and appetite suppressant . It was previously commonly used in prescription and over-the-counter cough and cold preparations . The medication is taken by mouth . Side effects of PPA include increased heart rate and blood pressure , among others. Rarely, PPA has been associated with hemorrhagic stroke . PPA acts as

114-453: A norepinephrine releasing agent , thereby indirectly activating adrenergic receptors . As such, it is an indirectly acting sympathomimetic . It was previously thought to act as a mixed acting sympathomimetic with additional direct agonist actions on adrenergic receptors, but this proved not to be the case. Chemically, PPA is a substituted amphetamine and is closely related to ephedrine , pseudoephedrine , amphetamine , and cathinone . It

171-542: A performance-enhancing drug in exercise and sports . However, clinical studies suggest that PPA is not effective in this regard. PPA is not on the World Anti-Doping Agency (WADA) list of prohibited substances as of 2024. In Sweden, PPA is still available in prescription decongestants; PPA is also still available in Germany. It is used in some polypill medications like Wick DayMed capsules. In

228-436: A drug is metabolized by a CYP450 enzyme and drug B blocks the activity of these enzymes, it can lead to pharmacokinetic alterations. A. This alteration results in drug A remaining in the bloodstream for an extended duration, and eventually increase in concentration. In some instances, the inhibition may reduce the therapeutic effect, if instead the metabolites of the drug is responsible for the effect. Compounds that increase

285-444: A drug's mechanism of action is affected by the concomitant administration of substances such as foods, beverages, or other drugs. A popular example of drug–food interaction is the effect of grapefruit on the metabolism of drugs . Interactions may occur by simultaneous targeting of receptors , directly or indirectly. For example, both Zolpidem and alcohol affect GABA A receptors , and their simultaneous consumption results in

342-428: A harmful interaction, including drugs with a narrow therapeutic index , where the difference between the effective dose and the toxic dose is small. The drug digoxin is an example of this type of drug. Risks are also increased when the drug presents a steep dose-response curve , and small changes in the dosage produce large changes in the drug's concentration in the blood plasma. As of 2008, among adults in

399-554: A high bioavailability . For this reason its administration is contraindicated in enteral feeding . Some drugs also alter absorption by acting on the P-glycoprotein of the enterocytes . This appears to be one of the mechanisms by which grapefruit juice increases the bioavailability of various drugs beyond its inhibitory activity on first pass metabolism . Drugs also may affect each other by competing for transport proteins in plasma , such as albumin . In these cases

456-546: A public health advisory against the use of the drug in November 2000. In this advisory, the FDA requested but did not require that all drug companies discontinue marketing products containing PPA. The agency estimates that PPA caused between 200 and 500 strokes per year among 18-to-49-year-old users. In 2005, the FDA removed PPA from over-the-counter sale and removed its "generally recognized as safe and effective" (GRASE) status. Under

513-570: A release of catecholamines , triggering symptoms that hint the organism to take action, like consuming sugary foods. If a patient is on insulin , which reduces blood sugar, and also beta-blockers , the body is less able to cope with an insulin overdose. Pharmacokinetics is the field of research studying the chemical and biochemical factors that directly affect dosage and the half-life of drugs in an organism, including absorption, transport, distribution, metabolism and excretion. Compounds may affect any of those process, ultimately interfering with

570-426: Is a small-molecule compound with the molecular formula C 9 H 13 NO and a molecular weight of 151.21   g/mol. It has an experimental log P of 0.67, while its predicted log P values range from 0.57 to 0.89. The compound is relatively lipophilic , but is also more hydrophilic than other amphetamines. The lipophilicity of amphetamines is closely related to their brain permeability. For comparison to PPA,

627-736: Is a substituted phenethylamine and amphetamine derivative . It is closely related to the cathinones (β-ketoamphetamines). β-Hydroxyamphetamine exists as four stereoisomers , which include d - ( dextrorotatory ) and l -norephedrine ( levorotatory ), and d - and l -norpseudoephedrine . d -Norpseudoephedrine is also known as cathine , and is found naturally in Catha edulis ( khat ). Pharmaceutical drug preparations of PPA have varied in their stereoisomer composition in different countries, which may explain differences in misuse and side effect profiles. In any case, racemic dl -norephedrine, or (1 RS ,2 SR )-phenylpropanolamine, appears to be

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684-485: Is a widely used direct-acting β 2 -agonist . Other examples include phenylephrine , isoproterenol , and dobutamine . Stimulation of the D1 receptor by dopaminergic agonists such as fenoldopam is used intravenously to treat hypertensive crisis . Dopaminergic stimulants such as amphetamine , ephedrine , and propylhexedrine work by causing the release of dopamine and norepinephrine, along with (in some cases) blocking

741-541: Is about 4   hours, with a range in different studies of 3.7 to 4.9   hours. The half-life of extended-release PPA has ranged from 4.3 to 5.8   hours. The elimination of PPA is dependent on urinary pH . At a more acidic urinary pH, the elimination of PPA is accelerated and its half-life and duration are shortened, whereas at more basic urinary pH, the elimination of PPA is reduced and its half-life and duration are extended. Urinary acidifying agents like ascorbic acid and ammonium chloride can increase

798-433: Is approximately 20%. However, it has been said that no recent studies have substantiated this value. PPA is not substantially metabolized . It also does not undergo significant first-pass metabolism . Only about 3 to 4% of an oral dose of PPA is metabolized. Metabolites include hippuric acid (via oxidative deamination of the side chain ) and 4-hydroxynorephedrine (via para - hydroxylation ). The methyl group at

855-779: Is its USAN Tooltip United States Adopted Name and BANM Tooltip British Approved Name in the case of the hydrochloride salt . It is also known by the synonym norephedrine . Brand names of PPA have included Acutrim, Appedrine, Capton Diet, Control, Dexatrim, Emagrin Plus A.P., Glifentol, Kontexin, Merex, Monydrin, Mydriatine, Prolamine, Propadrine, Propagest, Recatol, Rinexin, Tinaroc, and Westrim, among many others. It has also been used in combinations under brand names including Allerest, Demazin, Dimetapp, and Sinarest, among others. PPA remains available for medical and veterinary use in certain countries. There has been interest in PPA as

912-409: Is most commonly a racemic mixture of the (1 R ,2 S )- and (1 S ,2 R )- enantiomers of β-hydroxyamphetamine and is also known as dl -norephedrine. PPA was first synthesized around 1910 and its effects on blood pressure were first characterized around 1930. It was introduced for medical use by the 1930s. The medication was withdrawn from many markets starting in 2000 following findings that it

969-501: Is not extensively metabolized, it would probably not be affected by hepatic impairment . Conversely, there is likely to be accumulation of PPA with renal impairment due to its dependence on urinary excretion. Norephedrine is a minor metabolite of amphetamine and methamphetamine , as shown below. It is also a minor metabolite of ephedrine and a major metabolite of cathinone . PPA, also known as (1 RS ,2 SR )-α-methyl-β-hydroxyphenethylamine or as (1 RS ,2 SR )-β-hydroxyamphetamine,

1026-464: Is opposite to that of the main drug. These may be c ompetitive antagonists , if they compete with the main drug to bind with the receptor. or u ncompetitive antagonists, when the antagonist binds to the receptor irreversibly. The drugs can be considered heterodynamic competitors, if they act on distinct receptor with similar downstream pathways . The interaction my also occur via signal transduction mechanisms. For example, low blood glucose leads to

1083-454: Is readily- and well-absorbed with oral administration . Immediate-release forms of the drug reached peak levels about 1.5   hours (range 1.0 to 2.3   hours) following administration. Conversely, extended-release forms of PPA reach peak levels after 3.0 to 4.5   hours. The pharmacokinetics of PPA are linear across an oral dose range of 25 to 100   mg. Steady-state levels of PPA are achieved within 12   hours when

1140-723: Is still available either by prescription or sometimes over-the-counter. In Canada , it was withdrawn from the market on 31 May 2001. It was voluntarily withdrawn from the Australian market by July 2001. In India , human use of PPA and its formulations was banned on 10 February 2011, but the ban was overturned by the judiciary in September 2011. Phenylpropanolamine is the generic name of the drug and its INN Tooltip International Nonproprietary Name , BAN Tooltip British Approved Name , and DCF Tooltip Dénomination Commune Française , while phenylpropanolamine hydrochloride

1197-411: Is the case for oral anticoagulants and avocado . The formation of non-absorbable complexes may occur also via chelation , when cations can make certain drugs harder to absorb, for example between tetracycline or the fluoroquinolones and dairy products, due to the presence of calcium ions . . Other drugs bind to proteins. Some drugs such as sucralfate bind to proteins, especially if they have

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1254-710: Is used to control urinary incontinence in dogs. Stimulants: Phenylethanolamine Sympathomimetic agent These drugs can act through several mechanisms, such as directly activating postsynaptic receptors , blocking breakdown and reuptake of certain neurotransmitters, or stimulating production and release of catecholamines. The mechanisms of sympathomimetic drugs can be direct-acting (direct interaction between drug and receptor), such as α-adrenergic agonists , β-adrenergic agonists , and dopaminergic agonists ; or indirect-acting (interaction not between drug and receptor), such as MAOIs , COMT inhibitors , release stimulants, and reuptake inhibitors that increase

1311-579: The United Kingdom , PPA was available in many "all in one" cough and cold medications which usually also feature paracetamol or another analgesic and caffeine and could also be purchased on its own; however, it is no longer approved for human use. A European Category 1 Licence is required to purchase PPA for academic use. In the United States, the Food and Drug Administration (FDA) issued

1368-551: The blood–brain barrier , and limits its central nervous system (CNS) effects. Hence, PPA crosses into the brain only to some extent, has only weak CNS effects, and most of its effects are peripheral. In any case, PPA can produce amphetamine -like psychostimulant effects at very high doses. PPA is more lipophilic than structurally related sympathomimetics with hydroxyl groups on the phenyl ring like epinephrine (adrenaline) and phenylephrine and has greater brain permeability than these agents. The plasma protein binding of PPA

1425-540: The hydrochloride salt . PPA was first synthesized in the early 20th century, in or around 1910. It was patented as a mydriatic in 1913. The pressor effects of PPA were characterized in the late 1920s and the 1930s. PPA was first introduced for medical use by the 1930s. In the United States , PPA is no longer sold due to an increased risk of haemorrhagic stroke . In a few countries in Europe , however, it

1482-434: The mesial temporal areas of the brain. There has been very little research on drug interactions with PPA. In one study, PPA taken with caffeine was found to quadruple caffeine levels. In another study, PPA reduced theophylline clearance by 50%. PPA acts primarily as a selective norepinephrine releasing agent . It also acts as a dopamine releasing agent with around 10-fold lower potency . The stereoisomers of

1539-442: The precipitation of thiopentone. Pharmacodynamic interactions are the drug–drug interactions that occur at a biochemical level and depend mainly on the biological processes of organisms. These interactions occur due to action on the same targets; for example, the same receptor or signaling pathway . Pharmacodynamic interactions can occur on protein receptors . Two drugs can be considered to be homodynamic , if they act on

1596-492: The 2020 CARES Act , it requires FDA approval before it can be marketed again effectively banning the drug even as a prescription drug. Because of its potential use in amphetamine manufacture, PPA is controlled by the Combat Methamphetamine Epidemic Act of 2005 . It is still available for veterinary use in dogs, however, as a treatment for urinary incontinence . Internationally, an item on

1653-442: The absorption of other drugs such as zalcitabine , tipranavir and amprenavir . The opposite is more common, with, for example, the antacid cimetidine stimulating the absorption of didanosine . Some resources describe that a gap of two to four hours between taking the two drugs is needed to avoid the interaction. Factors such as food with high-fat content may also alter the solubility of drugs and impact its absorption. This

1710-637: The agenda of the 2000 Commission on Narcotic Drugs session called for including the stereoisomer norephedrine in Table I of United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances . Drugs containing PPA were banned in India on 27 January 2011. On 13 September 2011, Madras High Court revoked a ban on manufacture and sale of pediatric drugs PPA and nimesulide . PPA remains available for use in veterinary medicine . It

1767-428: The amine is primary or secondary, it will have direct action, but if the amine is tertiary, it will have poor direct action. Also, if the amine has bulky substituents, then it will have greater beta adrenergic receptor activity, but if the substituent is not bulky, then it will favor the alpha adrenergic receptors. Direct stimulation of the α- and β- adrenergic receptors can produce sympathomimetic effects. Salbutamol

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1824-471: The appearance of interactions include factors such as old age . This is where human physiology changing with age may affect the interaction of drugs. For example, liver metabolism, kidney function, nerve transmission, or the functioning of bone marrow all decrease with age. In addition, in old age, there is a sensory decrease that increases the chances of errors being made in the administration of drugs. The elderly are also more vulnerable to polypharmacy , and

1881-453: The chances of déjà vu occurring in the user, resulting in a strong sensation that an event or experience currently being experienced has already been experienced in the past. Some pharmaceutical drugs, when taken together, have also been implicated in the cause of déjà vu . The Journal of Clinical Neuroscience reported the case of an otherwise healthy male who started experiencing intense and recurrent sensations of déjà vu upon taking

1938-578: The drug have only weak or negligible affinity for α- and β-adrenergic receptors . PPA was originally thought to act as a direct agonist of adrenergic receptors and hence to act as a mixed acting sympathomimetic , However, PPA was subsequently found to show only weak or negligible affinity for these receptors and has been instead characterized as exclusively an indirectly acting sympathomimetic. It acts by inducing norepinephrine release and thereby indirectly activating adrenergic receptors. Many sympathetic hormones and neurotransmitters are based on

1995-467: The drug is taken once every 4   hours. There is 62% accumulation of PPA at steady state in terms of peak levels, whereas area-under-the-curve levels are not increased with steady state. The volume of distribution of PPA is 3.0 to 4.5   L/kg. Levels of PPA in the brain are about 40% of those in the heart and 20% of those in the lungs . The hydroxyl group of PPA at the β carbon increases its hydrophilicity , reduces its permeation through

2052-541: The drug that arrives first binds with the plasma protein, leaving the other drug dissolved in the plasma, modifying its expected concentration. The organism has mechanisms to counteract these situations (by, for example, increasing plasma clearance ), and thus they are not usually clinically relevant. They may become relevant if other problems are present, such as issues with drug excretion. Many drug interactions are due to alterations in drug metabolism . Further, human drug-metabolizing enzymes are typically activated through

2109-418: The drugs amantadine and PPA together to relieve flu symptoms. He found the experience so interesting that he completed the full course of his treatment and reported it to the psychologists to write up as a case study. Because of the dopaminergic action of the drugs and previous findings from electrode stimulation of the brain, it was speculated that déjà vu occurs as a result of hyperdopaminergic action in

2166-454: The efficiency of the enzymes, on the other hand, may have the opposite effect and increase the rate of metabolism. An example of this is shown in the following table for the CYP1A2 enzyme, showing the substrates (drugs metabolized by this enzyme) and some inductors and inhibitors of its activity: Some foods also act as inductors or inhibitors of enzymatic activity. The following table shows

2223-406: The engagement of nuclear receptors . One notable system involved in metabolic drug interactions is the enzyme system comprising the cytochrome P450 oxidases . Cytochrome P450 is a very large family of haemoproteins (hemoproteins) that are characterized by their enzymatic activity and their role in the metabolism of a large number of drugs. Of the various families that are present in humans,

2280-402: The excretion of and thereby reduce exposure to amphetamines including PPA, whereas urinary alkalinizing agents including antacids like sodium bicarbonate as well as acetazolamide can reduce the excretion of these agents and thereby increase exposure to them. Total body clearance of PPA has been reported to be 0.546   L/h/kg, while renal clearance was 0.432   L/h/kg. As PPA

2337-453: The experimental log P of methamphetamine is 2.1, of amphetamine is 1.8, of ephedrine is 1.1, of pseudoephedrine is 0.7, of phenylephrine is -0.3, and of norepinephrine is -1.2. Methamphetamine has high brain permeability, whereas phenylephrine and norepinephrine are peripherally selective drugs . The optimal log P for brain permeation and central activity is about 2.1 (range 1.5–2.7). PPA has been used pharmaceutically exclusively as

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2394-589: The flux of drugs in the human body , increasing or reducing drug availability. Drugs that change intestinal motility may impact the level of other drugs taken. For example, prokinetic agents increase the intestinal motility , which may cause drugs to go through the digestive system too fast, reducing absorption. The pharmacological modification of pH can affect other compounds. Drugs can be present in ionized or non-ionized forms depending on pKa , and neutral compounds are usually better absorbed by membranes. Medication like antacids can increase pH and inhibit

2451-469: The levels of endogenous catecholamines. A primary or secondary aliphatic amine separated by 2 carbons from a substituted benzene ring is minimally required for high agonist activity. The pKa of the amine is approximately 8.5-10. The presence of hydroxy group in the benzene ring at 3rd and 4th position shows maximum alpha- and beta-adrenergic activity. For maximum sympathomimetic activity, a drug must have: The structure can be modified to alter binding. If

2508-403: The more drugs a patient takes, the higher is the chance of an interaction. Genetic factors may also affect the enzymes and receptors, thus altering the possibilities of interactions. Patients with hepatic or renal diseases already may have difficulties metabolizing and excreting drugs, which may exacerbate the effect of interactions. Some drugs present an intrinsic increased risk for

2565-1551: The most common: Drugs tightly bound to proteins (i.e. not in the free fraction ) are not available for renal excretion . Filtration depends on a number of factors including the pH of the urine. Drug interactions may affect those points. Herb-drug interactions are drug interactions that occur between herbal medicines and conventional drugs. These types of interactions may be more common than drug-drug interactions because herbal medicines often contain multiple pharmacologically active ingredients, while conventional drugs typically contain only one. Some such interactions are clinically significant , although most herbal remedies are not associated with drug interactions causing serious consequences. Most catalogued herb-drug interactions are moderate in severity. The most commonly implicated conventional drugs in herb-drug interactions are warfarin , insulin , aspirin , digoxin , and ticlopidine , due to their narrow therapeutic indices . The most commonly implicated herbs involved in such interactions are those containing St. John’s Wort , magnesium, calcium, iron, or ginkgo . Examples of herb-drug interactions include, but are not limited to: The mechanisms underlying most herb-drug interactions are not fully understood. Interactions between herbal medicines and anticancer drugs typically involve enzymes that metabolize cytochrome P450 . For example, St. John's Wort has been shown to induce CYP3A4 and P-glycoprotein in vitro and in vivo. The factors or conditions that predispose

2622-433: The most commonly used formulation of PPA pharmaceutically. Analogues of PPA include ephedrine , pseudoephedrine , amphetamine , methamphetamine , and cathinone . PPA, structurally, is in the substituted phenethylamine class, consisting of a cyclic benzene or phenyl group, a two carbon ethyl moiety, and a terminal nitrogen, hence the name phen-ethyl-amine . The methyl group on the alpha carbon (the first carbon before

2679-477: The most interesting in this respect are the 1, 2 and 3, and the most important enzymes are CYP1A2 , CYP2C9 , CYP2C19 , CYP2D6 , CYP2E1 and CYP3A4 . The majority of the enzymes are also involved in the metabolism of endogenous substances, such as steroids or sex hormones , which is also important should there be interference with these substances. The function of the enzymes can either be stimulated ( enzyme induction ) or inhibited ( enzyme inhibition ). If

2736-556: The nitrogen group) also makes this compound a member of the substituted amphetamine class. Ephedrine is the N -methyl analogue of PPA. Exogenous compounds in this family are degraded too rapidly by monoamine oxidase to be active at all but the highest doses. However, the addition of the α-methyl group allows the compound to avoid metabolism and confer an effect. In general, N -methylation of primary amines increases their potency, whereas β-hydroxylation decreases CNS activity, but conveys more selectivity for adrenergic receptors. PPA

2793-732: The overstimulation of the receptor, which can lead to loss of consciousness. When two drugs affect each other, it is a drug–drug interaction (DDI) . The risk of a DDI increases with the number of drugs used. A large share of elderly people regularly use five or more medications or supplements, with a significant risk of side-effects from drug–drug interactions. Drug interactions can be of three kinds: It may be difficult to distinguish between synergistic or additive interactions, as individual effects of drugs may vary. Direct interactions between drugs are also possible and may occur when two drugs are mixed before intravenous injection . For example, mixing thiopentone and suxamethonium can lead to

2850-536: The phenethylamine skeleton, and function generally in "fight or flight" type responses, such as increasing heart rate, blood pressure, dilating the pupils, increased energy, drying of mucous membranes, increased sweating, and a significant number of additional effects. PPA has relatively low potency as a sympathomimetic. It is about 100 to 200   times less potent than epinephrine (adrenaline) or norepinephrine (noradrenaline) in its sympathomimetic effects, although responses are variable depending on tissue . PPA

2907-609: The reuptake of these neurotransmitters. Illegal drugs such as cocaine and MDMA also affect dopamine , serotonin , and norepinephrine . Norepinephrine is synthesized by the body from the amino acid tyrosine, and is used in the synthesis of epinephrine, which is a stimulating neurotransmitter of the central nervous system . All sympathomimetic amines fall into the larger group of stimulants (see psychoactive drug chart). In addition to intended therapeutic use, many of these stimulants have abuse potential , can induce tolerance , and possibly physical dependence , although not by

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2964-586: The same mechanism(s) as opioids or sedatives . The symptoms of physical withdrawal from stimulants can include fatigue, dysphoric mood, increased appetite, vivid or lucid dreams, hypersomnia or insomnia, increased movement or decreased movement, anxiety, and drug craving, as is apparent in the rebound withdrawal from certain substituted amphetamines . Sympathomimetic drugs are sometimes involved in development of cerebral vasculitis and generalized polyarteritis nodosa like diseases involving immune-complex deposition. Known reports of such hypersensitivity reactions include

3021-409: The same receptor. Homodynamic effects include drugs that act as (1) pure agonists , if they bind to the main locus of the receptor , causing a similar effect to that of the main drug, (2) partial agonists if, on binding to a secondary site, they have the same effect as the main drug, but with a lower intensity and (3) antagonists , if they bind directly to the receptor's main locus but their effect

3078-466: The use of pseudoephedrine , phenylpropanolamine , methamphetamine and other drugs at prescribed doses as well as at over-doses. " Parasympatholytic " and "sympathomimetic" have similar effects, but through completely different pathways. For example, both cause mydriasis , but parasympatholytics reduce accommodation ( cycloplegia ) while sympathomimetics do not. Drug interaction In pharmaceutical sciences , drug interactions occur when

3135-446: The α carbon of PPA blocks metabolism by monoamine oxidases (MAOs). PPA is also not a substrate of catechol O -methyltransferase . The hydroxyl group at the β carbon of PPA also helps to increase metabolic stability . Approximately 90% of a dose of PPA is excreted in the urine unchanged within 24   hours. About 4% of excreted material is in the form of metabolites . The elimination half-life of immediate-release PPA

3192-428: Was associated with increased risk of hemorrhagic stroke. It was previously available both over-the-counter and by prescription . PPA remains available for medical and/or veterinary use in some countries. PPA is used as a decongestant to treat nasal congestion . It has also been used to suppress appetite and promote weight loss in the treatment of obesity and has shown effectiveness for this indication. PPA

3249-437: Was previously available over-the-counter and in certain combination forms by prescription in the United States . However, these forms have all been discontinued. PPA remains available in certain other countries. PPA produces sympathomimetic effects and can cause side effects such as increased heart rate and blood pressure . It has been associated rarely with incidence of hemorrhagic stroke . Certain drugs increase

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