By W. Sven. Embry-Riddle Aeronautical University.
Figure 10: Dose-response curve Pharmacodynamics The effects of a drug are usually presented in a dose-response curve buy 2.5mg altace visa. The effect of the drug is plotted on the Y-axis and the dose on the X-axis (Figure 10) cheap altace 2.5mg free shipping. The higher the dose the stronger the effect order 2.5 mg altace, until the effect levels off to a maximum. However, the most accurate way is to use the plasma concentration, because it excludes differences in absorption and elimination of the drug. In the following text the plasma concentration-response curve (Cp/response curve) is used. The Cp/response curve The shape of the Cp/response curve is determined by pharmacodynamic factors. Cp/response curves reflect the result in a number of individuals, referred to as a ‘population’. If the plasma concentration is lower than where the curve begins, 0% of the population will experience an effect. An effect of 50% means that the average effect in the total population is 50% of the maximum (and not a 50% effect in one individual) (Figure 10). The concentration that gives the minimum useful effect is the therapeutic threshold, while the plasma concentration at which the maximum tolerated side effects occur is called the therapeutic ceiling. Remember that Cp/response curves represent the dynamics in a group of patients, and can only offer a guideline when thinking in terms of an individual patient. The plasma concentration in one or more patients during a certain period is depicted in a so called plasma concentration/time curve (Cp/time curve). This implies that if the dose is doubled, the steady state plasma concentration is also doubled (Figure 12). The Cp/time curve with a therapeutic window Two horizontal lines can be placed over the Cp/time curve, indicating therapeutic threshold and ceiling. Drug treatment aims at plasma concentrations within Figure 13: Cp/time curve and therapeutic window this therapeutic window. The possible variables to be considered are therefore (1) the position and the width of the window, and (2) the profile of the curve. Therapeutic window The position and the width of the window are determined by pharmacodynamic factors (Figure 14). The position of the window may shift upwards in case of resistance by the patient or competitive Figure 14: Place and width of antagonism by another drug: a higher plasma therapeutic window concentration is needed to exert the same effect. The window can shift downwards in case of hypersensitization or synergism by another drug: a lower plasma concentration is needed. For example, the therapeutic window of theophylline is narrower in small children than in adults. Curve The profile of the curve is determined by four factors: Absorption, Distribution, Metabolism and Excretion. Although most treatments consist of more than one dose of a drug, some pharmacokinetic parameters can best be explained by looking at the effect of one dose only. This means that per unit of time the same percentage of drug is eliminated, for example 6% per hour. The half-life of a drug is the time it takes to decrease the plasma concentration to half of its initial value. With 6% per hour the half-life is about 11 hours (if no more of the drug is given in the meantime). If the original plasma concentration falls within the therapeutic window, a decline to 6. For this reason it is usually said that drugs no longer have a pharmacological effect 4 half-lives after the last dose. Drug treatment The total Cp/time curve is influenced by three actions by the prescriber: starting the drug-treatment; steady state treatment; stopping the treatment. Starting drug treatment The most important issue in starting treatment is Figure 16: Steady state is reached the speed at which the curve reaches steady after 4 half-lives state, within the therapeutic window. If you give a fixed dose per unit of time, this speed is only determined by the half-life of the drug. On a fixed dosage schedule, steady state is reached after about 4 half-lives (Figure 16). In case of a long half-life it may therefore take some time for the drug to reach a therapeutic concentration. Steady state drug treatment 102 Annex 1 In steady state drug treatment two aspects are Figure 17: Dose dependent important.
The plasma concentrations of atovaquone and proguanil in women in the second A and third trimesters of pregnancy are approximately half those of non-pregnant 5 adults (with and without acute malaria) as a result of a greater Vd and increased oral clearance generic 10mg altace fast delivery. Pharmacokinetic parameters of atovaquone cheap altace 5 mg line, proguanil and cycloguanil in studies of currently recommended doses for malaria prophylaxis or treatment (range of mean or median values reported) altace 5mg lowest price. Parameter Atovaquone Proguanil Cycloguanil Cmax (ng/mL) 634–13 270 560–751 37–67 Tmax (h) 5. The side-effects of atovaquone– proguanil are similar in children and adults (9, 14). The most common adverse effects reported are headache, cough and gastrointestinal disturbances (such as abdominal pain, nausea, vomiting and diarrhoea). Other adverse events occur rarely, such as dizziness and oral ulceration, and, very rarely, blood disorders including neutropenia and anaemia and skin reactions such as photosensitivity rash and erythema multiforme. Allergic reactions including anaphylaxis, angioedema, Stevens–Johnson syndrome and vasculitis may rarely occur. Pancytopenia in patients with severe renal impairment treated with proguanil has been reported, probably because of drug accumulation (15). Contraindications Atovaquone–proguanil is contraindicated in patients with known serious hypersensitivity reactions to atovaquone or proguanil. It is also contraindicated as malaria prophylaxis in patients with severe renal impairment because of the high risk for pancytopenia. The main concern is the approximate twofold reduction in plasma concentrations of both atovaquone and proguanil (7, 8), which could leave pregnant women more susceptible to malaria infection or at risk for treatment failure. Additional strategies are strongly advised for pregnant women taking atovaquone– proguanil for malaria prevention. Prolonged protection provided by a single dose of atovaquone–proguanil for the chemoprophylaxis of Plasmodium falciparum malaria in a human challenge model. The pharmacokinetics of atovaquone and proguanil in pregnant women with acute falciparum malaria. The pharmacokinetics and pharmacodynamics of atovaquone and proguanil for the treatment of uncomplicated falciparum malaria in third- trimester pregnant women. Sabchareon A, Attanath P, Phanuaksook P, Chanthavanich P, Poonpanich Y, Mookmanee D, et al. Effcacy and pharmacokinetics of atovaquone and proguanil in children with multidrug-resistant Plasmodium falciparum malaria. Lower atovaquone/proguanil concentrations in patients taking efavirenz, lopinavir/ritonavir or atazanavir/ritonavir. Chloroquine is extensively distributed in body tissues and fuids, including the placenta and breast milk. The drug is eliminated slowly from the body , with ~55% eliminated via the kidneys. Pharmacokinetic properties of chloroquine and desethylchloroquine in studies of currently recommended doses for malaria prophylaxis or treatment (range of mean or median values reported). Parameter Chloroquine Desethylchloroquine Cmax (ng/mL) 283–1430 89–220 Tmax (h) 2. The chloroquine concentrations achieved are reportedly lower during pregnancy, particularly in the second and third trimesters (11,21), although one studies showed no such difference (20). Large doses used for 5 the treatment of rheumatoid arthritis are associated with a higher frequency of adverse events than the lower doses used in malaria. Other less common side- effects include headache, hepatitis, elevated liver enzyme, various skin eruptions and gastrointestinal disturbances, such as nausea, vomiting and diarrhoea. More rarely, central nervous system toxicity, including convulsions and mental changes, may occur. Chronic use (> 5 years continuous use as prophylaxis) may lead to eye disorders, including keratopathy and retinopathy. Other uncommon effects include myopathy, reduced hearing, photosensitivity and hair loss. The patient may progress from feeling dizzy and drowsy with headache and gastrointestinal upset, to sudden visual loss, convulsions, hypokalaemia, hypotension and cardiac arrhythmia. Contraindications Chloroquine is contraindicated in patients with known hypersensitivity to chloroquine or any aminoquinoline compounds. The drug should also be administered with caution to patients with retinal or visual impairment or hepatic impairment. From methylene blue to chloroquine: a brief review of the development of an antimalarial therapy. Recent developments in the understanding of the pharmacokinetics and mechanism of action of chloroquine. Pharmacokinetics of sequential and simultaneous treatment with the combination chloroquine and sulfadoxine–pyrimethamine in acute uncomplicated Plasmodium falciparum malaria in the Philippines. The pharmacokinetics and electrocardiographic effects of chloroquine in healthy subjects. The pharmacokinetics of chloroquine in healthy Thai subjects and patients with Plasmodium vivax malaria. The pharmacokinetics of three multiple dose regimens of chloroquine: implications for malaria chemoprophylaxis.
However purchase altace 2.5 mg online, Podofilox (podophyllotoxin) is a patient-applied antimitotic limited data exist regarding the efficacy or risk for complications drug that causes wart necrosis cheap 2.5mg altace. Treatment regimens are cotton swab) or podofilox gel (using a finger) should be applied classified as either patient-applied or provider-administered to anogenital warts twice a day for 3 days generic 10 mg altace with mastercard, followed by 4 days modalities. This cycle can be repeated, as necessary, for up persons because they can be administered in the privacy of to four cycles. To ensure that patient-applied modalities are 10 cm2, and the total volume of podofilox should be limited effective, instructions should be provided to patients while in to 0. Sinecatechins 15% ointment are provider-applied caustic agents that destroy warts by should be applied three times daily (0. Although these preparations ointment to each wart) using a finger to ensure coverage with are widely used, they have not been investigated thoroughly. This product should not be continued for longer water and can spread rapidly and damage adjacent tissues if than 16 weeks (774–776). If pain is intense or an common side effects of sinecatechins are erythema, pruritus/ excess amount of acid is applied, the area can be covered with burning, pain, ulceration, edema, induration, and vesicular sodium bicarbonate (i. The safety of sinecatechins during Alternative Regimens for External Genital Warts pregnancy is unknown. Cryotherapy is a provider-applied therapy that destroys warts Less data are available regarding the efficacy of alternative by thermal-induced cytolysis. Health-care providers must be regimens for treating anogenital warts, which include trained on the proper use of this therapy because over- and podophyllin resin, intralesional interferon, photodynamic under-treatment can result in complications or low efficacy. Further, alternative regimens Pain during and after application of the liquid nitrogen, might be associated with more side effects. Podophyllin resin 10%–25% in a compound requires substantial clinical training, additional equipment, and tincture of benzoin might be considered for provider- sometimes a longer office visit. After local anesthesia is applied, administered treatment under conditions of strict adherence anogenital warts can be physically destroyed by electrocautery, to recommendations. Podophyllin should be applied to each in which case no additional hemostasis is required. Care must wart and then allowed to air-dry before the treated area comes be taken to control the depth of electrocautery to prevent into contact with clothing. Alternatively, the warts can be removed either by air-dry can result in local irritation caused by spread of the tangential excision with a pair of fine scissors or a scalpel, by compound to adjacent areas and possible systemic toxicity. To avoid the warts are exophytic, this procedure can be accomplished with possibility of complications associated with systemic absorption a resulting wound that only extends into the upper dermis. Suturing is neither required nor open lesions, wounds, or friable tissue; and 3) the preparation indicated in most cases. In patients with large or extensive should be thoroughly washed off 1–4 hours after application. Shelf-life and stability warts, particularly for those persons who have not responded of podophyllin preparations are unknown. Treatment of anogenital and oral warts podophyllin during pregnancy has not been established. Recommended Regimens for Vaginal Warts Counseling Cryotherapy with liquid nitrogen. The use of a cryoprobe in the vagina is not recommended because of the risk for vaginal perforation and Key Messages for Persons with Anogenital Warts fistula formation. Sexual activity should be avoided with new partners until the warts are gone or removed. Most anogenital warts respond within 3 months of • Condoms might lower the chances of transmitting genital therapy. This vaccine can prevent most cases of side effects; treatment response and therapy-associated side genital warts in persons who have not yet been exposed effects should be evaluated throughout the course of therapy. Persistent hypopigmentation or hyperpigmentation Management of Sex Partners can occur with ablative modalities (e. Special Considerations Cervical Cancer Pregnancy Podofilox (podophyllotoxin), podophyllin, and sinecatechins Screening Recommendations should not be used during pregnancy. Imiquimod appears Recommendations for cervical cancer screening in the United to pose low risk but should be avoided until more data are States are based on systematic evidence reviews and are largely available. Anogenital warts can proliferate and become friable consistent across the major medical organizations, including during pregnancy. Instead, Pap testing is recommended every 3 years Pregnant women with anogenital warts should be counseled from ages 21–29 years. Squamous cell carcinomas arising in or be provided with general recommendations regarding when resembling anogenital warts might occur more frequently to schedule follow-up visits and the importance of cervical among immunosuppressed persons, therefore requiring biopsy cancer screening. Women with abnormal screening tests should for confirmation of diagnosis for suspicious cases (786–788). The cytology can differentiate cells from blood and mucus; importance and frequency of Pap testing or co-testing (Pap conventional Pap test might not). However, in most instances (even in 1) cervical cancer screening in conjunction with a Pap test, the presence of some severe infections), Pap tests will be 2) triage of abnormal cervical cytology results, and 3) follow-up reported as satisfactory for evaluation, and reliable final after treatment of cervical precancers. These tests are only reports can be produced without the need to repeat the approved for use with cervical specimens, not oral or anal Pap test after treatment is received.