Posts Tagged ‘Doses’

Bosentan
Type of Drug     Endothelia receptor antagonist.
Prescribed For
Pulmonary arterial hypertension.
General Information
These drugs lower blood pressure by working on the endothelin system. Endothelia is a hormone that plays an important role in maintaining blood pressure. It is normally found in blood vessels, but endothelin levels are very high in the blood and lungs of people with pulmonary arterial hypertension. People with this condition have high blood pressure, trouble breathing, and get very tired even when walking or doing other moderate exercising. Pulmonary arterial hypertension can be fatal.
Cautions and Warnings
These drugs should not be used by those who are allergic or sensitive to any of their ingredients.
Bosentan can cause liver injury. People taking these drugs should have their liver enzymes checked monthly. Enzyme increases can be a sign of liver injury and may be a reason to stop taking bosentan.
These drugs are broken down in the liver. People with liver damage should take them with caution.
These drugs should not be taken during pregnancy as they are likely to cause birth defects (see “Special Populations”).
These drugs cause a reduction in red blood cells, leading to anemia. Larger doses of bosentan cause a greater loss of red blood cells.
Possible Side Effects
Ambrisentan
Most side effects are mild. Only stuffy nose increases with increased dosage.
V Most common: swelling k%) -aims or legs, stuffy nose, si1)u6fis, flushing, heart palpitations, abdominal pain, constipation, difficulty breathing, and headache.
Bosentan
♦ Most common: headache and sore throat and nose.
Drug Interactions
•    It is possible that bosentan may cause failure of hormonal contraceptives.
•    Cyclosporine, used to prevent transplant rejection, increases blood levels of bosentan and ambrisentan. Do not combine these drugs.
•    Mixing glyburide, an antidiabetes drug, with bosentan increases the risk of elevated liver enzyme levels. Do not combine these drugs.
•    Ketoconazole greatly increases blood levels of bosentan by slowing its breakdown in the liver.
•    Combining bosentan with a statin-type cholesterol - lowering drug such as simvastatin, lovastatin, or atorvastatin reduces the amount of statin drug in the blood. Dose increases may be needed.
•    Bosentan can reduce the amount of warfarin in the blood by
about 1/3. Changes in warfarin dosage may be needed.
•    Combining ambrisentan with atanazavir, clarithromycin, indinavir, itraconazole, ketoconazole, nelfinavir, ritonavir, omeprazole, saquinavir,or telithromycin may increase the amount of ambrisentan in the blood. Caution is advised.
•    Combining ambrisentan with rifampin may reduce the
amount of ambrisentan in the blood. Caution is advised.
Food Interactions
These drugs may be taken with or without food.
U’Suk Dose
Ambrisentan
Adult (age 18 and over): 5-10 mg once a day. Do not crush, split, or chew these tablets.
Child: not recommended.
Possible Side Effects (continued)
♦    Common: flushing, abnormal liver blood pressure, and heart
♦    Less common: upset stomach, tiredness.
ver function, leg swelling, palpitations.
, swelling, itching, anemia,
Bosentan
Adult (age 18 and over): 62.5 mg twice a day for 4 weeks, then
125 mg twice a day.
Child: not recommended.
Overdosage
Massive overdose may result in severe lowering of blood pressure, requiring emergency attention. The most common effects associated with overdosage are headache, low blood pressure, increased heart rate, and nausea and vomiting. Overdose victims should be taken to a hospital emergency room for treatment. ALWAYS bring the prescription bottle or container.
Special Information
Do not stop taking these drugs without gradually reducing the dosage as instructed by your doctor.
If you forget to take a dose, take it as soon as you remember. If it is almost time for your next dose, skip the dose you forgot and continue with your regular schedule. Do not take a double dose.
Contact your doctor at once if you develop severe itching, yellowing of the skin or eyes, tiredness, swelling in the arms or legs, nausea, vomiting, fever, or abdominal pain.
Doctors must enroll in special restricted distribution programs before they can prescribe these medicines, because of the risks of liver injury and birth defects associated with them. These medicines are not available in regular pharmacies but are mailed to you from a central pharmacy only after the testing and other program requirements have been met by your doctor.
Special Populations
Pregnancy/Breast-feeding: These medicines are very likely to cause major birth defects and should not be taken by pregnant women. Women must be sure they are not pregnant before beginning these treatments.
Women should also use non-hormone contraceptives while on these drugs. Hormone-based contraceptives such as birth control pills, injections, and implants may not work in women taking Wst m or ambrisentan.
It is not known if either of these medicines passes into breast milk. Nursing mothers should use infant formula.
Seniors: The greater chance of kidney, liver, and cardiac function side effects in seniors may affect drug dosage. Seniors may also experience more swelling in the arms or legs.

Drug compliance
It must be admitted that relatively few patients leave the consulting room with a clear idea of the nature and dose of the prescribed medication, partly as a result of fear of th
and partly because of the difficulties of understanding complex therapy. Here, nurses can play a valuable part in reducing difficulties and misunderstandings, particularly when dealing with the elderly and/or confused patient, and it is often helpful to ask patients to repeat the directions that they believe they have been given. Misunderstandings and errors can then be cleared
up at an early stage. The containers of the dispensed medicines should bear not
only the name of the drug, but also useful additional information such as The Heart Tablets’ or ‘The Water Tablets’. Vague directions should be avoided: whenever possible definite times for administration of drugs should be arranged. Such timing can be linked with some regular activity, such as a meal time, or a favourite TV programme may be used as a memory aid for regular dosing. With multiple therapy, patients should be encouraged to set each day’s dose aside, so that a double dose of a drug will not be taken by forgetfulness. Patients should be advised that the occasional missed dose is not always important, and a missed dose should not be made up by taking a double dose later on.
Although regular dosing is important in securing patient compliance, many modern drugs have relatively long half-lives so the regular administration of full doses for long periods may lead to overdose. The ideal dose depends on many factors, including absorption, metabolism, transport and excretion, but in many cases the margin of safety is fairly wide. In the elderly, however, reduced renal efficiency may lead to the gradual accumulation of a drug with insidious toxic effects. Many elderly patients, for example, on digoxin, may become overdivitalized because of poor metabolism and excretion of the drug. It is by no
means unknown for elderly and confused patients, once admitted to hospital for observation, to make an apparently surprising recovery from an illness that was basically due to over-medication, often as a result of following blindly a misunderstood drug regimen. It is here that the community nurse has an exceptionally valuable part to play in ensuring regular and accurate medication, and reporting any incipient signs of overdose or side-effects.
Ail increasing problem of current therapy is patient compliance with prescribed treatment. It is easy for a doctor to prescribe, but to ensure that the patient takes the prescribed drugs in the right dose is a very different matter. The magnitude of the problem has increased with the rise in multiple therapy, and the reluctance on the part of some doctors to prescribe mixed products.

Notes on dosage
In this dictionary of drugs, the doses, unless otherwise stated, are average daily doses for adults, and are normally given as divided doses at suitable intervals. An indication is given of those few drugs that are taken as a single daily dose, or where
the dose is based on the surface area of the body expressed as square metres (ml).
When a dose range is indicated, a small initial dose is often followed by gradually increasing doses according to need and response, but with long-acting drugs care must be taken to avoid excessive dosage, as such drugs may then accumulate in the body and have toxic side-effects. It should be noted that the side-effects of a drug may prevent the administration of an optimum therapeutic dose, and a recommended dose is often a compromise between activity and toxicity. The gap is sometimes referred to as the ‘therapeutic window’, and the wider the gap the safer the drug.
Dosage is also influenced by the route of administration, as oral doses are normally larger than those given by intramuscular injection, and the latter are in turn larger than those given intravenously. The weight, age and sex of a patient may also have to be taken into account when assessing dosage. Renal and hepatic
-impairment may require an adjustment of dose, whereas if tolerance to a drug
develops, a larger dose may be required to evoke an adequate response. Dosage
also requires particular care during pregnancy if toxic effects on the fetus are to be avoided and, ideally, no drug should be given in pregnancy unless the need outweighs the risks.
Doses for infants also present problems. Their drug-detoxifying enzyme
systems and renal excretory capabilities are not fully developed although,
paradoxically, they have higher metabolic rates than adults, and so may sometimes require an apparently relatively high dose of a drug.

Doses for the elderly also frequently require modification, as their reduced renal efficiency may cause accumulation of the drug and increase susceptibility to toxic effects, unless reduced doses are given. Elderly patients are, in any case, more susceptible to nephrotic drugs generally. Hepatic disease may also increase drug toxicity as liver enzymes play a major part in drug metabolism, and severe liver disease may give rise to a drug toxicity that might not otherwise occur. Hyperlipidaemic drugs, fusidic acid and some antifungal agents of the ketoconazole type are examples of drugs best avoided in hepatic disease. Multiple therapy may also lead to an increased and not always appreciated incidence of drug toxicity. For further information on these important aspects of drug dosage, a book for nurses on drugs and pharmacology should be consulted.

Controlled drugs
Drugs likely to cause dependence and misuse are referred to as ‘controlled drugs’ (CDs), as they are subject to the strict prescription requirements of the Misuse of Drugs Act, 1971, and are distinguished in this book by a dagger t. They include opium, morphine, heroin (diamorphine), pethidine and other synthetic, potent analgesics/narcotics, dihydrocodeine injection, barbiturates (except intravenous anaesthetics) and amphetamines. Controlled drugs can be supplied only on receipt of a hand-written prescription from the prescriber, giving full details of the patient, the drug, the form and strength of the prescription to be dispensed, and the total amount to be supplied expressed in both words and figures. Certain weak preparations of some controlled drugs, such as Kaolin and Morphine Mixture for diarrhoea, with which misuse is unlikely, are exempt from control, and can be obtained without prescription.