Adverse effects may be local, i.e. limited to a certain location, or systemic, where a medication has caused adverse effects throughout the systemic circulation.

For instance, some ocular antihypertensives cause systemic effects, although they are administered locally as eye drops, since a fraction escapes to the systemic circulation.

Causality assessment is used to determine the likelihood that a drug caused a suspected ADR. There are a number of different methods used to judge causation, including the Naranjo algorithm, the Venulet algorithm and the WHO causality term assessment criteria. Each have pros and cons associated with their use and most require some level of expert judgement to apply.

An ADR should not be labeled as 'certain' unless the ADR abates with a challenge-dechallenge-rechallenge protocol (stopping and starting the agent in question). The chronology of the onset of the suspected ADR is important, as another substance or factor may be implicated as a cause; co-prescribed medications and underlying psychiatric conditions may be factors in the ADR.

Assigning causality to a specific agent often proves difficult, unless the event is found during a clinical study or large databases are used. Both methods have difficulties and can be fraught with error. Even in clinical studies some ADRs may be missed as large numbers of test individuals are required to find that adverse drug reaction. Psychiatric ADRs are often missed as they are grouped together in the questionnaires used to assess the population.

Within all classes of medicinal drugs that possibly can lead to pulmonary toxicity as a side effect, most pulmonary toxicity is due to chemotherapy for cancer.

Many medicinal drugs can lead to pulmonary toxicity. A few medicinal drugs can lead to pulmonary toxicity frequently (in medicine defined by international regulatory authorities such as the U.S. Food and Drug Administration and the EMEA [European Union] as > 1% and 10%). These medicinal drugs can include gold and nitrofurantoin, as well as the following drugs used in chemotherapy for cancer: Methotrexate, the taxanes (paclitaxel and docetaxel), gemcitabine, bleomycin, mitomycin C, busulfan, cyclophosphamide, chlorambucil, and nitrosourea (e.g., carmustine).

Also, some medicinal drugs used in cardiovascular medicine can lead to pulmonary toxicity frequently or very frequently. These include above all amiodarone, as well as beta blockers, ACE inhibitors (however, pulmonary toxicity of ACE inhibitors usually lasts only 3–4 months and then usually disappears by itself), procainamide, quinidine, tocainide, and minoxidil.

Both oncologists and cardiologists are well aware of possible pulmonary toxicity.

The "medical benefit-cost ratio" for the patient should be kept in mind. Medicinal drugs should not be ruled out completely right from the start just because they possibly could cause pulmonary toxicity. A number of medicinal drugs that could cause pulmonary toxicity can be life-saving for certain patients with specific diseases. For example, amiodarone falls into this category. Ideally, the pros and cons should be weighed at the start of therapy and in regular intervals thereafter, based on the available scientific/medical evidence, by an expert physician, together with an informed patient.

Acute infection does not usually require treatment and most adults clear the infection spontaneously. Early antiviral treatment may be required in fewer than 1% of people, whose infection takes a very aggressive course (fulminant hepatitis) or who are immunocompromised. On the other hand, treatment of chronic infection may be necessary to reduce the risk of cirrhosis and liver cancer. Chronically infected individuals with persistently elevated serum alanine aminotransferase, a marker of liver damage, and HBV DNA levels are candidates for therapy. Treatment lasts from six months to a year, depending on medication and genotype. Treatment duration when medication is taken by mouth, however, is more variable and usually longer than one year.

Although none of the available drugs can clear the infection, they can stop the virus from replicating, thus minimizing liver damage. As of 2008, there are seven medications licensed for the treatment of infection in the United States. These include antiviral drugs lamivudine (Epivir), adefovir (Hepsera), tenofovir (Viread), telbivudine (Tyzeka) and entecavir (Baraclude), and the two immune system modulators interferon alpha-2a and PEGylated interferon alpha-2a (Pegasys). In 2015 the World Health Organization recommended tenofovir or entecavir as first-line agents. Those with current cirrhosis are in most need of treatment.

The use of interferon, which requires injections daily or thrice weekly, has been supplanted by long-acting PEGylated interferon, which is injected only once weekly. However, some individuals are much more likely to respond than others, and this might be because of the genotype of the infecting virus or the person's heredity. The treatment reduces viral replication in the liver, thereby reducing the viral load (the amount of virus particles as measured in the blood). Response to treatment differs between the genotypes. Interferon treatment may produce an e antigen seroconversion rate of 37% in genotype A but only a 6% seroconversion in type D. Genotype B has similar seroconversion rates to type A while type C seroconverts only in 15% of cases. Sustained e antigen loss after treatment is ~45% in types A and B but only 25–30% in types C and D.

Some cases of myotonia congenita do not require treatment, or it is determined that the risks of the medication outweigh the benefits. If necessary, however, symptoms of the disorder may be relieved with quinine, phenytoin, carbamazepine, mexiletine and other anticonvulsant drugs. Physical therapy and other rehabilitative measures may also be used to help muscle function. Genetic counseling is available.

The treatment should be tailored to the cause involved and the severity of the disease process. With oral osteoporosis the emphasis should be on good nutrient absorption and metabolic wastes elimination through a healthy gastro-intestinal function, effective hepatic metabolism of toxicants such as exogenous estrogens, endogenous acetaldehyde and heavy metals, a balanced diet, healthy lifestyle, assessment of factors related to potential coagulopathies, and treatment of periodontal diseases and other oral and dental infections.

In cases of advanced oral ischaemic osteoporosis and/or ONJ that are not bisphosphonates related, clinical evidence has shown that surgically removing the damaged marrow, usually by curettage and decortication, will eliminate the problem (and the pain) in 74% of patients with jaw involvement. Repeat surgeries, usually smaller procedures than the first, may be required. Almost a third of jawbone patients will need surgery in one or more other parts of the jaws because the disease so frequently present multiple lesions, i.e., multiple sites in the same or similar bones, with normal marrow in between. In the hip, at least half of all patients will get the disease in the opposite hip over time; this pattern occurs in the jaws as well. Recently, it has been found that some osteonecrosis patients respond to anticoagulation therapies alone. The earlier the diagnosis the better the prognosis. Research is ongoing on other non-surgical therapeutic modalities that could alone or in combination with surgery further improve the prognosis and reduce the morbidity of ONJ. A greater emphasis on minimizing or correcting known causes is necessary while further research is conducted on chronic ischaemic bone diseases such as oral osteoporosis and ONJ.

In patients with bisphosphonates-associated ONJ, the response to surgical treatment is usually poor. Conservative debridement of necrotic bone, pain control, infection management, use of antimicrobial oral rinses, and withdrawal of bisphosphonates are preferable to aggressive surgical measures for treating this form of ONJ. Although an effective treatment for bisphosphonate-associated bone lesions has not yet been established, and this is unlikely to occur until this form of ONJ is better understood, there have been clinical reports of some improvement after 6 months or more of complete cessation of bisphosphonate therapy.

In assisted reproductive technology, sperm washing is not necessary for males with hepatitis B to prevent transmission, unless the female partner has not been effectively vaccinated. In females with hepatitis B, the risk of transmission from mother to child with IVF is no different from the risk in spontaneous conception.

Those at high risk of infection should be tested as there is effective treatment for those who have the disease. Groups that screening is recommended for include those who have not been vaccinated and one of the following: people from areas of the world where hepatitis B occurs in more than 2%, those with HIV, intravenous drug users, men who have sex with men, and those who live with someone with hepatitis B.

Congenital myotonia, also called myotonia congenita, is a congenital neuromuscular channelopathy that affects skeletal muscles (muscles used for movement). It is a genetic disorder. The hallmark of the disease is the failure of initiated contraction to terminate, often referred to as delayed relaxation of the muscles (myotonia) and rigidity. Symptoms include delayed relaxation of the muscles after voluntary contraction (myotonia), and may also include stiffness, hypertrophy (enlargement), transient weakness in some forms of the disorder (from certain genetic mutations), and cramping. The condition is sometimes referred to as fainting goat syndrome, as it is responsible for the eponymous 'fainting' seen in fainting goats when presented with a sudden stimulus.

The first three cases of bisphosphonate-associated osteonecrosis of the jaw were spontaneously reported to the FDA by an oral surgeon in 2002, with the toxicity being described as a potentially late toxicity of chemotherapy. In 2003 and 2004, three oral surgeons independently reported to the FDA information on 104 cancer patients with bisphosphonate-associated osteonecrosis of the jaw seen in their referral practices in California, Florida, and New York. These case series were published as peer-reviewed articles — two in the "Journal of Oral and Maxillofacial Surgery" and one in the "Journal of Clinical Oncology". Subsequently, numerous instances of persons with this ADR were reported to the manufacturers and to the FDA. By December 2006, 3607 cases of people with this ADR had been reported to the FDA and 2227 cases had been reported to the manufacturer of intravenous bisphosphonates.

The International Myeloma Foundation's web-based survey included 1203 respondents, 904 patients with myeloma and 299 with breast cancer and an estimate that after 36 months, osteonecrosis of the jaw had been diagnosed in 10% of 211 patients on zoledronate and 4% of 413 on pamidronate. A population based study in Germany identified more than 300 cases of osteonecrosis of the jaw, 97% occurring in cancer patients (on high-dose intravenous bisphosphonates) and 3 cases in 780,000 patients with osteoporosis for an incidence of 0.00038%. Time to event ranged from 23–39 months and 42–46 months with high dose intravenous and oral bisphosphonates. A prospective, population based study by Mavrokokki "et al.". estimated an incidence of osteonecrosis of the jaw of 1.15% for intravenous bisphosphonates and 0.04% for oral bisphosphonates. Most cases (73%) were precipitated by dental extractions. In contrast, safety studies sponsored by the manufacturer reported bisphosphonate-associated osteonecrosis of the jaw rates that were much lower.

Although the majority of cases of ONJ have occurred in cancer patients receiving high dose intravenous bisphosphonates, almost 800 cases have been reported in oral bisphosphonate users for osteoporosis or Pagets disease. In terms of severity most cases of ONJ in oral bisphosphonate users are stage 1–2 and tend to progress to resolution with conservative measures such as oral chlorhexidine rinses.

Owing to prolonged embedding of bisphosphonate drugs in the bone tissues, the risk for BRONJ is high even after stopping the administration of the medication for several years.

This form of therapy has been shown to prevent loss of bone mineral density (BMD) as a result of a reduction in bone turnover. However, bone health entails quite a bit more than just BMD. There are many other factors to consider.

In healthy bone tissue there is a homeostasis between bone resorption and bone apposition. Diseased or damaged bone is resorbed through the osteoclasts mediated process while osteoblasts form new bone to replace it, thus maintaining healthy bone density. This process is commonly called remodelling.

However, osteoporosis is essentially the result of a lack of new bone formation in combination with bone resorption in reactive hyperemia, related to various causes and contributing factors, and bisphosphonates do not address these factors at all.

In 2011, a proposal incorporating both the reduced bone turnover and the infectious elements of previous theories has been put forward. It cites the impaired functionality of affected macrophages as the dominant factor in the development of ONJ.

In a systematic review of cases of bisphosphonate-associated ONJ up to 2006, it was concluded that the mandible is more commonly affected than the maxilla (2:1 ratio), and 60% of cases are preceded by a dental surgical procedure. According to Woo, Hellstein and Kalmar, oversuppression of bone turnover is probably the primary mechanism for the development of this form of ONJ, although there may be contributing co-morbid factors (as discussed elsewhere in this article). It is recommended that all sites of potential jaw infection should be eliminated before bisphosphonate therapy is initiated in these patients to reduce the necessity of subsequent dentoalveolar surgery. The degree of risk for osteonecrosis in patients taking oral bisphosphonates, such as alendronate (Fosamax), for osteoporosis is uncertain and warrants careful monitoring. Patients taking dexamethasone and other glucocorticoids are at increased risk.

Matrix metalloproteinase 2 may be a candidate gene for bisphosphonate-associated osteonecrosis of the jaw, since it is the only gene known to be associated with bone abnormalities and atrial fibrillation, both of which are side effects of bisphosphonates.