Dexamfetamine interactions

INDIRECT ANALGESICS Dexamfetamine and methylphenidate t the analgesic effects and 1 the sedation of opioids when used for chronic pain Uncertain complex interaction between the sympathetic nervous system and the opioid receptors Opioid requirements may be 1 when patients also take indirect sympathomimetics... 

INDIRECT ANTIPSYCHOTICS 1. Case reports of paralytic ileus with trifluoperazine and methylphenidate 2. Case report of acute dystonias with haloperidol and dexamfetamine 3.1 efficacy of chlorpromazine when dexamfetamine was added 1. Additive anticholinergic effect 2. Uncertain possibly due to t dopamine release 3. Uncertain 1. Watch for signs of altered bowel habit 2. Warn patients of this rare interaction 3. Avoid co-administration... 

Interactions. Morphine (also pethidine and possibly other opioids) is potentiated by monoamine oxidase inhibitors. Any central nervous system depressant (including alcohol) will have additive effects. Patients recently exposed to neuromuscular blocking agents (unless this is adequately reversed, e.g. by neostigmine) are particularly at risk from the respiratory depressant effects of morphine. The effect of diuretic drugs may be reduced by release of antidiuretic hormone by morphine. Useful interactions include the potientating effect on pain relief of tricyclic antidepressants and of dexamfetamine. 

In narcolepsy, patients usually need a stimulant for their hypersomnia and a TCA or SSRI for their cataplexy, so care should be taken when combining these. Dexamfetamine and methylphenidate must not be given with MAOIs. There is potential for interaction between methylphenidate and TCAs (hyperteirsion) and SSRI antidepressants. It appears that modafinil, methylphenidate and dexamfeta-mine may themselves be combined without adverse outcome (modafinil is occasionally used regularly and dexamfetamine added intermittently when peak alertness is particularly critical). Modafinil accelerates the metabolism of oral contraceptives, reducing their efficacy. 

Anorectic drugs, which are structurally related to the amphetamines, act mainly on the satiety centre in the hypothalamus and also increase general physical activity (1). All of them, except fenfluramine, stimulate the central nervous system and can cause restlessness, nervousness, irritabihty, and insomnia. Adverse effects also occur through sympathetic stimulation and gastrointestinal irritation. Drug interactions can occur with monoamine oxidase inhibitors. Dexamfetamine, phenmetrazine, and benzfetamine can cause dependence. Some of them have been associated with cardiac valvulopathy and primary pulmonary hypertension (2). 

Anorectic drugs act mainly on the satiety centre in the hypothalamus (1). They also have metabohc effects involving fat and carbohydrate metaboUsm. Most of them are structurally related to amfetamine and increase physical activity. Their therapeutic effect tends to abate after some months, and part of this reduction in effect may be due to chemical alterations in the brain. Fenfluramine commonly produces drowsiness in normal doses, but has stimulaut effects in overdosage. Dexamfetamine, phenmetrazine, and benzfetamine all tend to cause euphoria, with a risk of addiction. Euphoria occasionally occurs with amfepramone (diethylpropion), phentermine, and chlorphentermine, but to a much lesser extent. Some adverse effects are due to sympathetic stimulation and gastrointestinal irritation these may necessitate withdrawal but are never serious. There are interactions with monoamine oxidase inhibitors and antihypertensive drugs. 

The potential for an interaction of modafinil with dexamfetamine, each at steady state, has been investigated in an open, randomized study in 32 healthy subjects (13). All took modafinil orally once daily for 28 days (200 mg on days 1-7 and 400 mg on days 8-28). On days 22-28, half of... 

The appetite suppressant and other effects of amfetamines, chlo-rphentermine and phenmetrazine are opposed by chlorpro-mazine. It seems possible that other phenothiazine will interact similarly. The antipsychotic effects of chlorpromazine can be opposed by dexamfetamine. 

This interaction has been deliberately exploited, with success, in the treatment of 22 children poisoned with various amfetamines or related compounds (amfetamine, dexamfetamine, metamfetamine, phenmetrazine). ... 

Established interactions. These reports suggest that it is not beneficial to attempt to treat patients taking chlorpromazine with amfetamines, such as dexamfetamine, or other central stimulants such as phenmetrazine. In one study, thioridazine also appeared to interact. However, it is not clear whether this interaction takes place with antipsychotics other than chlorpromazine, but it seems possible with the phenothiazines, especially if the suggested mechanism is correct. Note that central stimulants are no longer recommended for the treatment of obesity. 

No pharmacokinetic interaction appears to occur between modafinil and dexamfetamine. 

The concurrent use of non-selective MAOIs and amfetamines and related drugs can result in a potentially fatal hypertensive crisis and/or serotonin syndrome. Interactions have been reported for amfetamine, dexamfetamine, metamfetamine, and methylpheni-date. Interactions have also been reported with the illicit drug ecstasy (MDMA, methylenedioxymethamfetamine) when taken with phenelzine or moclobemide. The manufacturers of fenfluramine and dexfenfluramine contraindicated their use with MAOIs. 

Methylphenidate can increase the levels and rate of response to tricyclic antidepressants. This has led to both increased beneficial and adverse effects. No significant pharmacokinetic interaction has been reported between desipramine and dexamfetamine or methylphenidate. An isolated report describes a blood dyscrasia in a child given methylphenidate and imipramine. 

In contrast, a retrospective review in 142 children and adolescents taking either desipramine alone, or desipramine with dexamfetamine or methylphenidate, indicated the absence of a clinically significant interaction between desipramine and either stimulant. Pharmacokinetic parameters were similar in each group. ... 

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