INFORMATION FOR HEALTH PROFESSIONALS
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Phentermine HCl in:
30mg sustained release capsule: A size 2 capsule having a green cap and clear body filled with white to off-white beadlets.
Phentermine is an indirect acting sympathomimetic agent with both alpha- and beta-adrenergic activity. Its actions include stimulation of the central nervous system, and elevation of blood pressure. Tachyphylaxis and tolerance may develop. Phentermine is an anorectic agent, however, it has not been established that its action in treating obesity is primarily one of appetite suppression. Other mechanisms may be involved.
Short-term clinical trials have shown that adult obese subjects treated by dietary management and "anorectic agents" lose more weight on average than those treated with placebo and diet.
Phentermine is readily absorbed from the gastrointestinal tract, peak concentrations being expected between 2-4 hours after oral administration. It distributes readily and since it is structurally related to amphetamine, can be expected to appear in breast milk. Duration of action may be up to 12-14 hours.
Dimethyl substitution on the α-carbon of the benzene ring side chain means phentermine is resistant to oxidation by monoamine oxidase so that elimination occurs by biotransformation in the liver and renal excretion.
The half-life of phentermine has been measured as between 19-24 hours. Urinary elimination is pH dependent and enhanced in acid urine.
Umine is indicated as a short-term adjunct in a medically monitored comprehensive regimen of weight reduction based on exercise, diet (caloric restriction) and behaviour modification in obese patients with a body mass index (BMI) of = 30kg/m2 who have not achieved an adequate clinical response to an approppriate weight-reducing regimen alone. Patients with the following co-morbidities are particular candidates for medical assistance with weight reduction, and may be considered for treatment even if their BMI does not exceed 30kg/m2.
Failure to achieve a weight reduction of 5% within a period of 12 weeks is an indication for discontinuation of treatment. Treatment may continue beyond this point provided continued monitoring of the patient occurs (for weight loss and medical conditions) and for as long as weight loss is maintained.
Secondary organic causes for obesity should be excluded by diagnosis before prescribing this agent.
Umine Timedcaps 30mg are taken orally, the dose being 30mg each morning. To reduce the risk of dependence, the maximum continuous period of treatment should not exceed four to eight weeks (followed by similar period without treatment).
Children and the elderly - not recommended.
Umine Timedcaps should not be used in: agitated patients, alcoholic patients either active or in remission, advanced arteriosclerosis, the presence of symptomatic cardiovascular disease including arrhythmias, patients with a history of or actively abusing drugs or being dependent on drugs, glaucoma, moderate to severe hypotension, hyperthyroidism.
Tolerance to the anorectic effect may occur in which case the medicine should be discontinued. Phentermine HCl may impair the ability of the patient to engage in potentially hazardous activities such as operating machinery, driving a vehicle. Since phentermine HCl is related chemically and pharmacologically to the amphetamines, there is a possibility that it may be abused. Abuse may be associated with intense psychological dependence and severe social dysfunction. There are reports of patients who have increased the dosage to many times that recommended.
Abrupt cessation after prolonged high dose administration results in extreme fatigue, mental depression and changes in the sleep EEG. Chronic intoxication may result in severe dermatoses, marked insomnia, irritability, hyperactivity, personality changes, the most severe of which is psychosis, often clinically indistinguishable from schizophrenia.
Insulin requirements in diabetes mellitus may be altered in association with the use of phentermine HCl such that strict monitoring of blood glucose concentrations is required.
Do not use in pregnancy. There is inadequate evidence of safety in human pregnancy and there is no information from animal studies.
Concurrent administration of phentermine HCl with alcohol is not recommended since this may increase possible CNS effects such as dizziness, lightheadedness, fainting and confusion. Chronic use of phentermine HCl prior to anaesthesia may result in cardiac arrhythmias because these anaesthetics sensitise the myocardium to the effects of sympathomimetics. Dosage adjustment of hypoglycaemics may be required during and subsequent to phentermine HCl use because of altered insulin requirements.
Valvular heart disease had been reported in association with fenfluramine or dexfenfluramine in combination with phentermine, but not with phentermine alone. Umine is not recommended for use in those with pre-existing valvular heart disease, although there is no evidence showing that phentermine alters the course of valvular heart disease. Primary pulmonary hypertension has been reported with medicines used for weight loss, and its association with phentermine cannot be ruled out.
Umine should not be used in men or women for loss of weight for cosmetic reasons.
Umine should not be used by children or adolescents or during pregnancy or lactation.
Those who have failed to respond to medical treatment for weight loss in the past should only be treated after review by a medical practitioner specialising in the treatment of weight loss.
The ability of the patient to maintain effective lifestyle interventions of exercise and diet, and adhere to a medical regimen should be assessed before treatment is commenced.
The adverse effects of phentermine HCl are commonly symptoms of overstimulation of the central nervous system and include insomnia, nervousness, restlessness, irritability, and euphoria that may be followed by fatigue and depression. There may be dryness of the mouth, anorexia, abdominal cramps and other gastrointestinal disturbances, headache, dizziness, tremor, sweating, tachycardia, palpitations, increased blood pressure, difficulty in micturition, altered libido, and impotence. Psychotic reactions have occurred as has muscle damage with associated renal complications.
In acute overdosage, the adverse effects are accentuated and may be accompanied by hyperpyrexia, mydriasis, hyperreflexia, chest pain, cardiac arrhythmias, confusion, panic states, aggressive behaviour, hallucinations, delirium, convulsion, respiratory depression, coma, circulatory collapse and death.
Individual patient response may vary widely and toxic manifestations may occur at relatively low doses.
Phentermine HCl may interfere with the hypotensive effects of clonidine, guanethidine and methyldopa. Concurrent use with thyroid hormones may increase CNS stimulation.
Phentermine HCl should not be administered during or within 14 days following administration of MAO inhibitors since concurrent use may potentiate sympathomimetic effects possibly resulting in a hypertensive crisis. Chlorpromazine may antagonise the anorectic effect of phentermine HCl.
The co-administration of phentermine with fenfluramine is not recommended, due to the possibility of heart valve abnormalities and/or pulmonary hypertension.
Serotonin reuptake inhibitors and tricyclic antidepressants may interact with Umine by increasing serotonin levels, and Umine should be used with caution in those taking these agents.
Overdosage with phentermine manifests as: restlessness, tremor, hyperreflexia, rapid respiration, confusion, assaultive behaviour with hallucinations and panic states. The above result from central stimulation and are usually followed by fatigue and depression.
Cardiovascular effects are also possible and include arrhythmias, hypertension or hypotension and circulatory collapse.
Other symptoms include nausea, vomiting, diarrhoea and abdominal cramps. If fatal, death is usually preceded by convulsions and coma.
Management of acute phentermine intoxication is largely symptomatic and includes lavage and barbiturate sedation.
Acidification of the urine increases excretion. The effect of haemodialysis or peritoneal dialysis is unknown.
Acute severe hypertension complicating phentermine overdose should be treated by appropriate intravenous therapy.
Store below 30°C. Protect from light and moisture. Keep out of reach of children.
Controlled Drug C5.
100 sustained release capsules.
Phentermine HCl is benzene ethanamine,α,α-dimethyl-,hydrochloride. It has a molecular formula and weight of C10H15N.HCl and 185.7 respectively.
Other ingredients of the capsules are: Sucrose, Maize starch, Stearic acid, Shellac, Polivinylpyrrolidinone, and Talc.
Douglas Pharmaceuticals Ltd
P O Box 45-027
AUCKLAND 8
Ph: (09) 835 0660
Fax: (09) 835 0665
3 November 2000